Rename Root to ArtifactRoot. This is slightly more descriptive, and we will potentially want to use the name Root for a broader concept shared between ArtifactRoot and RootedPath. PiperOrigin-RevId: 182082367

diff --git a/src/main/java/com/google/devtools/build/lib/actions/Artifact.java b/src/main/java/com/google/devtools/build/lib/actions/Artifact.java
index 7468de1..a72c77d 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/Artifact.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/Artifact.java

@@ -164,7 +164,7 @@
 
   private final int hashCode;
   private final Path path;
-  private final Root root;
+  private final ArtifactRoot root;
   private final PathFragment execPath;
   private final PathFragment rootRelativePath;
   private final ArtifactOwner owner;
@@ -176,18 +176,20 @@
    *
    * <p>In a source Artifact, the path tail after the root will be identical to the execPath, but
    * the root will be orthogonal to execRoot.
+   *
    * <pre>
    *  [path] == [/root/][execPath]
    * </pre>
    *
    * <p>In a derived Artifact, the execPath will overlap with part of the root, which in turn will
    * be below the execRoot.
+   *
    * <pre>
    *  [path] == [/root][pathTail] == [/execRoot][execPath] == [/execRoot][rootPrefix][pathTail]
    * </pre>
    */
   @VisibleForTesting
-  public Artifact(Path path, Root root, PathFragment execPath, ArtifactOwner owner) {
+  public Artifact(Path path, ArtifactRoot root, PathFragment execPath, ArtifactOwner owner) {
     if (root == null || !path.startsWith(root.getPath())) {
       throw new IllegalArgumentException(root + ": illegal root for " + path
           + " (execPath: " + execPath + ")");
@@ -233,7 +235,7 @@
    * <pre>
    */
   @VisibleForTesting
-  public Artifact(Path path, Root root, PathFragment execPath) {
+  public Artifact(Path path, ArtifactRoot root, PathFragment execPath) {
     this(path, root, execPath, ArtifactOwner.NULL_OWNER);
   }
 
@@ -241,17 +243,15 @@
    * Constructs a source or derived Artifact for the specified path and specified root. The root
    * must be an ancestor of the path.
    */
-  @VisibleForTesting  // Only exists for testing.
-  public Artifact(Path path, Root root) {
+  @VisibleForTesting // Only exists for testing.
+  public Artifact(Path path, ArtifactRoot root) {
     this(path, root, root.getExecPath().getRelative(path.relativeTo(root.getPath())),
         ArtifactOwner.NULL_OWNER);
   }
 
-  /**
-   * Constructs a source or derived Artifact for the specified root-relative path and root.
-   */
-  @VisibleForTesting  // Only exists for testing.
-  public Artifact(PathFragment rootRelativePath, Root root) {
+  /** Constructs a source or derived Artifact for the specified root-relative path and root. */
+  @VisibleForTesting // Only exists for testing.
+  public Artifact(PathFragment rootRelativePath, ArtifactRoot root) {
     this(root.getPath().getRelative(rootRelativePath), root,
         root.getExecPath().getRelative(rootRelativePath), ArtifactOwner.NULL_OWNER);
   }
@@ -347,13 +347,15 @@
 
   /**
    * Returns the root beneath which this Artifact resides, if any. This may be one of the
-   * package-path entries (for source Artifacts), or one of the bin, genfiles or includes dirs
-   * (for derived Artifacts). It will always be an ancestor of getPath().
+   * package-path entries (for source Artifacts), or one of the bin, genfiles or includes dirs (for
+   * derived Artifacts). It will always be an ancestor of getPath().
    */
-  @SkylarkCallable(name = "root", structField = true,
-      doc = "The root beneath which this file resides."
+  @SkylarkCallable(
+    name = "root",
+    structField = true,
+    doc = "The root beneath which this file resides."
   )
-  public final Root getRoot() {
+  public final ArtifactRoot getRoot() {
     return root;
   }
 
@@ -443,7 +445,11 @@
     private final SpecialArtifactType type;
 
     @VisibleForTesting
-    public SpecialArtifact(Path path, Root root, PathFragment execPath, ArtifactOwner owner,
+    public SpecialArtifact(
+        Path path,
+        ArtifactRoot root,
+        PathFragment execPath,
+        ArtifactOwner owner,
         SpecialArtifactType type) {
       super(path, root, execPath, owner);
       this.type = type;

diff --git a/src/main/java/com/google/devtools/build/lib/actions/ArtifactFactory.java b/src/main/java/com/google/devtools/build/lib/actions/ArtifactFactory.java
index 37bd6f4..26d97f7 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ArtifactFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ArtifactFactory.java

@@ -145,7 +145,7 @@
   }
 
   @Override
-  public Artifact getSourceArtifact(PathFragment execPath, Root root, ArtifactOwner owner) {
+  public Artifact getSourceArtifact(PathFragment execPath, ArtifactRoot root, ArtifactOwner owner) {
     Preconditions.checkArgument(!execPath.isAbsolute(), "%s %s %s", execPath, root, owner);
     Preconditions.checkNotNull(owner, "%s %s", execPath, root);
     execPath = execPath.normalize();
@@ -153,11 +153,11 @@
   }
 
   @Override
-  public Artifact getSourceArtifact(PathFragment execPath, Root root) {
+  public Artifact getSourceArtifact(PathFragment execPath, ArtifactRoot root) {
     return getSourceArtifact(execPath, root, ArtifactOwner.NULL_OWNER);
   }
 
-  private void validatePath(PathFragment rootRelativePath, Root root) {
+  private void validatePath(PathFragment rootRelativePath, ArtifactRoot root) {
     Preconditions.checkArgument(!root.isSourceRoot());
     Preconditions.checkArgument(!rootRelativePath.isAbsolute(), rootRelativePath);
     Preconditions.checkArgument(rootRelativePath.isNormalized(), rootRelativePath);
@@ -177,8 +177,8 @@
    * computed as {@code root.getRelative(rootRelativePath).relativeTo(root.execRoot)}.
    */
   // TODO(bazel-team): Don't allow root == execRootParent.
-  public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root,
-      ArtifactOwner owner) {
+  public Artifact getDerivedArtifact(
+      PathFragment rootRelativePath, ArtifactRoot root, ArtifactOwner owner) {
     validatePath(rootRelativePath, root);
     Path path = root.getPath().getRelative(rootRelativePath);
     return getArtifact(path, root, path.relativeTo(root.getExecRoot()), owner, null);
@@ -192,8 +192,8 @@
    * <p>The root must be below the execRootParent, and the execPath of the resulting Artifact is
    * computed as {@code root.getRelative(rootRelativePath).relativeTo(root.execRoot)}.
    */
-  public Artifact getFilesetArtifact(PathFragment rootRelativePath, Root root,
-      ArtifactOwner owner) {
+  public Artifact getFilesetArtifact(
+      PathFragment rootRelativePath, ArtifactRoot root, ArtifactOwner owner) {
     validatePath(rootRelativePath, root);
     Path path = root.getPath().getRelative(rootRelativePath);
     return getArtifact(
@@ -201,22 +201,22 @@
   }
 
   /**
-   * Returns an artifact that represents a TreeArtifact; that is, a directory containing some
-   * tree of ArtifactFiles unknown at analysis time.
+   * Returns an artifact that represents a TreeArtifact; that is, a directory containing some tree
+   * of ArtifactFiles unknown at analysis time.
    *
    * <p>The root must be below the execRootParent, and the execPath of the resulting Artifact is
    * computed as {@code root.getRelative(rootRelativePath).relativeTo(root.execRoot)}.
    */
-  public Artifact getTreeArtifact(PathFragment rootRelativePath, Root root,
-      ArtifactOwner owner) {
+  public Artifact getTreeArtifact(
+      PathFragment rootRelativePath, ArtifactRoot root, ArtifactOwner owner) {
     validatePath(rootRelativePath, root);
     Path path = root.getPath().getRelative(rootRelativePath);
     return getArtifact(
         path, root, path.relativeTo(root.getExecRoot()), owner, SpecialArtifactType.TREE);
   }
 
-  public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, Root root,
-      ArtifactOwner owner) {
+  public Artifact getConstantMetadataArtifact(
+      PathFragment rootRelativePath, ArtifactRoot root, ArtifactOwner owner) {
     validatePath(rootRelativePath, root);
     Path path = root.getPath().getRelative(rootRelativePath);
     return getArtifact(
@@ -225,12 +225,15 @@
   }
 
   /**
-   * Returns the Artifact for the specified path, creating one if not found and
-   * setting the <code>root</code> and <code>execPath</code> to the
-   * specified values.
+   * Returns the Artifact for the specified path, creating one if not found and setting the <code>
+   * root</code> and <code>execPath</code> to the specified values.
    */
-  private synchronized Artifact getArtifact(Path path, Root root, PathFragment execPath,
-      ArtifactOwner owner, @Nullable SpecialArtifactType type) {
+  private synchronized Artifact getArtifact(
+      Path path,
+      ArtifactRoot root,
+      PathFragment execPath,
+      ArtifactOwner owner,
+      @Nullable SpecialArtifactType type) {
     Preconditions.checkNotNull(root);
     Preconditions.checkNotNull(execPath);
 
@@ -250,7 +253,11 @@
     return artifact;
   }
 
-  private Artifact createArtifact(Path path, Root root, PathFragment execPath, ArtifactOwner owner,
+  private Artifact createArtifact(
+      Path path,
+      ArtifactRoot root,
+      PathFragment execPath,
+      ArtifactOwner owner,
       @Nullable SpecialArtifactType type) {
     Preconditions.checkNotNull(owner, path);
     if (type == null) {
@@ -261,13 +268,15 @@
   }
 
   /**
-   * Returns an {@link Artifact} with exec path formed by composing {@code baseExecPath} and
-   * {@code relativePath} (via {@code baseExecPath.getRelative(relativePath)} if baseExecPath is
-   * not null). That Artifact will have root determined by the package roots of this factory if it
-   * lives in a subpackage distinct from that of baseExecPath, and {@code baseRoot} otherwise.
+   * Returns an {@link Artifact} with exec path formed by composing {@code baseExecPath} and {@code
+   * relativePath} (via {@code baseExecPath.getRelative(relativePath)} if baseExecPath is not null).
+   * That Artifact will have root determined by the package roots of this factory if it lives in a
+   * subpackage distinct from that of baseExecPath, and {@code baseRoot} otherwise.
    */
   public synchronized Artifact resolveSourceArtifactWithAncestor(
-      PathFragment relativePath, PathFragment baseExecPath, Root baseRoot,
+      PathFragment relativePath,
+      PathFragment baseExecPath,
+      ArtifactRoot baseRoot,
       RepositoryName repositoryName) {
     Preconditions.checkState(
         (baseExecPath == null) == (baseRoot == null),
@@ -288,10 +297,10 @@
     if (isDerivedArtifact(execPath)) {
       return null;
     }
-    Root sourceRoot = findSourceRoot(execPath, baseExecPath, baseRoot, repositoryName);
+    ArtifactRoot sourceRoot = findSourceRoot(execPath, baseExecPath, baseRoot, repositoryName);
     Artifact artifact = sourceArtifactCache.getArtifactIfValid(execPath);
     if (artifact != null) {
-      Root artifactRoot = artifact.getRoot();
+      ArtifactRoot artifactRoot = artifact.getRoot();
       Preconditions.checkState(
           sourceRoot == null || sourceRoot.equals(artifactRoot),
           "roots mismatch: %s %s %s",
@@ -308,8 +317,10 @@
    * root directory if our execPath doesn't start with baseExecPath due to uplevel references.
    */
   @Nullable
-  private Root findSourceRoot(
-      PathFragment execPath, @Nullable PathFragment baseExecPath, @Nullable Root baseRoot,
+  private ArtifactRoot findSourceRoot(
+      PathFragment execPath,
+      @Nullable PathFragment baseExecPath,
+      @Nullable ArtifactRoot baseRoot,
       RepositoryName repositoryName) {
     PathFragment dir = execPath.getParentDirectory();
     if (dir == null) {
@@ -323,7 +334,7 @@
     }
 
     while (dir != null && !dir.equals(baseExecPath)) {
-      Root sourceRoot =
+      ArtifactRoot sourceRoot =
           packageRoots.getRootForPackage(PackageIdentifier.create(repositoryName, dir));
       if (sourceRoot != null) {
         return sourceRoot;
@@ -365,7 +376,8 @@
         unresolvedPaths.add(execPath);
       }
     }
-    Map<PathFragment, Root> sourceRoots = resolver.findPackageRootsForFiles(unresolvedPaths);
+    Map<PathFragment, ArtifactRoot> sourceRoots =
+        resolver.findPackageRootsForFiles(unresolvedPaths);
     // We are missing some dependencies. We need to rerun this method later.
     if (sourceRoots == null) {
       return null;
@@ -380,7 +392,7 @@
   public Path getPathFromSourceExecPath(PathFragment execPath) {
     Preconditions.checkState(
         !execPath.startsWith(derivedPathPrefix), "%s is derived: %s", execPath, derivedPathPrefix);
-    Root sourceRoot =
+    ArtifactRoot sourceRoot =
         packageRoots.getRootForPackage(PackageIdentifier.create(RepositoryName.MAIN, execPath));
     if (sourceRoot != null) {
       return sourceRoot.getPath().getRelative(execPath);
@@ -388,7 +400,7 @@
     return execRoot.getRelative(execPath);
   }
 
-  private Artifact createArtifactIfNotValid(Root sourceRoot, PathFragment execPath) {
+  private Artifact createArtifactIfNotValid(ArtifactRoot sourceRoot, PathFragment execPath) {
     if (sourceRoot == null) {
       return null;  // not a path that we can find...
     }

diff --git a/src/main/java/com/google/devtools/build/lib/actions/ArtifactResolver.java b/src/main/java/com/google/devtools/build/lib/actions/ArtifactResolver.java
index 7542118..2b543d2 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ArtifactResolver.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ArtifactResolver.java

@@ -34,15 +34,15 @@
    * @param owner the artifact owner.
    * @return the canonical source artifact for the given path
    */
-  Artifact getSourceArtifact(PathFragment execPath, Root root, ArtifactOwner owner);
+  Artifact getSourceArtifact(PathFragment execPath, ArtifactRoot root, ArtifactOwner owner);
 
   /**
    * Returns the source Artifact for the specified path, creating it if not found and setting its
    * root and execPath.
    *
-   * @see #getSourceArtifact(PathFragment, Root, ArtifactOwner)
+   * @see #getSourceArtifact(PathFragment, ArtifactRoot, ArtifactOwner)
    */
-  Artifact getSourceArtifact(PathFragment execPath, Root root);
+  Artifact getSourceArtifact(PathFragment execPath, ArtifactRoot root);
 
   /**
    * Resolves a source Artifact given an execRoot-relative path.

diff --git a/src/main/java/com/google/devtools/build/lib/actions/Root.java b/src/main/java/com/google/devtools/build/lib/actions/ArtifactRoot.java
similarity index 83%
rename from src/main/java/com/google/devtools/build/lib/actions/Root.java
rename to src/main/java/com/google/devtools/build/lib/actions/ArtifactRoot.java
index 27c6898..47b3c5e 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/Root.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ArtifactRoot.java

@@ -44,16 +44,19 @@
  * <p>The derived roots must have paths that point inside the exec root, i.e. below the directory
  * that is the root of the merged directory tree.
  */
-@SkylarkModule(name = "root",
-    category = SkylarkModuleCategory.BUILTIN,
-    doc = "A root for files. The roots are the directories containing files, and they are mapped "
-        + "together into a single directory tree to form the execution environment.")
+@SkylarkModule(
+  name = "root",
+  category = SkylarkModuleCategory.BUILTIN,
+  doc =
+      "A root for files. The roots are the directories containing files, and they are mapped "
+          + "together into a single directory tree to form the execution environment."
+)
 @Immutable
-public final class Root implements Comparable<Root>, Serializable, SkylarkValue {
+public final class ArtifactRoot implements Comparable<ArtifactRoot>, Serializable, SkylarkValue {
 
   // This must always be consistent with Package.getSourceRoot; otherwise computing source roots
   // from exec paths does not work, which can break the action cache for input-discovering actions.
-  public static Root computeSourceRoot(Path packageRoot, RepositoryName repository) {
+  public static ArtifactRoot computeSourceRoot(Path packageRoot, RepositoryName repository) {
     if (repository.isMain()) {
       return asSourceRoot(packageRoot);
     } else {
@@ -66,8 +69,8 @@
   }
 
   /** Returns the given path as a source root. The path may not be {@code null}. */
-  public static Root asSourceRoot(Path path) {
-    return new Root(null, path);
+  public static ArtifactRoot asSourceRoot(Path path) {
+    return new ArtifactRoot(null, path);
   }
 
   /**
@@ -77,17 +80,17 @@
    * <p>Be careful with this method - all derived roots must be registered with the artifact factory
    * before the analysis phase.
    */
-  public static Root asDerivedRoot(Path execRoot, Path root) {
+  public static ArtifactRoot asDerivedRoot(Path execRoot, Path root) {
     Preconditions.checkArgument(root.startsWith(execRoot));
     Preconditions.checkArgument(!root.equals(execRoot));
-    return new Root(execRoot, root);
+    return new ArtifactRoot(execRoot, root);
   }
 
-  public static Root middlemanRoot(Path execRoot, Path outputDir) {
+  public static ArtifactRoot middlemanRoot(Path execRoot, Path outputDir) {
     Path root = outputDir.getRelative("internal");
     Preconditions.checkArgument(root.startsWith(execRoot));
     Preconditions.checkArgument(!root.equals(execRoot));
-    return new Root(execRoot, root, true);
+    return new ArtifactRoot(execRoot, root, true);
   }
 
   @Nullable private final Path execRoot;
@@ -95,14 +98,14 @@
   private final boolean isMiddlemanRoot;
   private final PathFragment execPath;
 
-  private Root(@Nullable Path execRoot, Path path, boolean isMiddlemanRoot) {
+  private ArtifactRoot(@Nullable Path execRoot, Path path, boolean isMiddlemanRoot) {
     this.execRoot = execRoot;
     this.path = Preconditions.checkNotNull(path);
     this.isMiddlemanRoot = isMiddlemanRoot;
     this.execPath = isSourceRoot() ? PathFragment.EMPTY_FRAGMENT : path.relativeTo(execRoot);
   }
 
-  private Root(@Nullable Path execRoot, Path path) {
+  private ArtifactRoot(@Nullable Path execRoot, Path path) {
     this(execRoot, path, false);
   }
 
@@ -138,7 +141,7 @@
   }
 
   @Override
-  public int compareTo(Root o) {
+  public int compareTo(ArtifactRoot o) {
     return path.compareTo(o.path);
   }
 
@@ -152,10 +155,10 @@
     if (o == this) {
       return true;
     }
-    if (!(o instanceof Root)) {
+    if (!(o instanceof ArtifactRoot)) {
       return false;
     }
-    Root r = (Root) o;
+    ArtifactRoot r = (ArtifactRoot) o;
     return path.equals(r.path) && Objects.equals(execRoot, r.execRoot);
   }
 

diff --git a/src/main/java/com/google/devtools/build/lib/actions/MiddlemanFactory.java b/src/main/java/com/google/devtools/build/lib/actions/MiddlemanFactory.java
index fbbc100..43a9e37 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/MiddlemanFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/MiddlemanFactory.java

@@ -45,15 +45,15 @@
    *
    * @param owner the owner of the action that will be created; must not be null
    * @param purpose the purpose for which this middleman is created. This should be a string which
-   *        is suitable for use as a filename. A single rule may have many middlemen with distinct
-   *        purposes.
+   *     is suitable for use as a filename. A single rule may have many middlemen with distinct
+   *     purposes.
    * @param inputs the set of artifacts for which the created artifact is to be the middleman.
    * @param middlemanDir the directory in which to place the middleman.
    * @return null iff {@code inputs} is empty; the single element of {@code inputs} if there's only
-   *         one; a new aggregating middleman for the {@code inputs} otherwise
+   *     one; a new aggregating middleman for the {@code inputs} otherwise
    */
   public Artifact createAggregatingMiddleman(
-      ActionOwner owner, String purpose, Iterable<Artifact> inputs, Root middlemanDir) {
+      ActionOwner owner, String purpose, Iterable<Artifact> inputs, ArtifactRoot middlemanDir) {
     if (hasExactlyOneInput(inputs)) { // Optimization: No middleman for just one input.
       return Iterables.getOnlyElement(inputs);
     }
@@ -64,28 +64,26 @@
   }
 
   /**
-   * Returns <code>null</code> iff inputs is empty. Returns the sole element
-   * of inputs iff <code>inputs.size()==1</code>. Otherwise, returns a
-   * middleman artifact and creates a middleman action that generates that
-   * artifact.
+   * Returns <code>null</code> iff inputs is empty. Returns the sole element of inputs iff <code>
+   * inputs.size()==1</code>. Otherwise, returns a middleman artifact and creates a middleman action
+   * that generates that artifact.
    *
    * @param owner the owner of the action that will be created.
-   * @param owningArtifact the artifact of the file for which the runfiles
-   *        should be created. There may be at most one set of runfiles for
-   *        an owning artifact, unless the owning artifact is null. There
-   *        may be at most one set of runfiles per owner with a null
-   *        owning artifact.
-   *        Further, if the owning Artifact is non-null, the owning Artifacts'
-   *        root-relative path must be unique and the artifact must be part
-   *        of the runfiles tree for which this middleman is created. Usually
-   *        this artifact will be an executable program.
-   * @param inputs the set of artifacts for which the created artifact is to be
-   *        the middleman.
+   * @param owningArtifact the artifact of the file for which the runfiles should be created. There
+   *     may be at most one set of runfiles for an owning artifact, unless the owning artifact is
+   *     null. There may be at most one set of runfiles per owner with a null owning artifact.
+   *     Further, if the owning Artifact is non-null, the owning Artifacts' root-relative path must
+   *     be unique and the artifact must be part of the runfiles tree for which this middleman is
+   *     created. Usually this artifact will be an executable program.
+   * @param inputs the set of artifacts for which the created artifact is to be the middleman.
    * @param middlemanDir the directory in which to place the middleman.
    */
   public Artifact createRunfilesMiddleman(
-      ActionOwner owner, @Nullable Artifact owningArtifact, Iterable<Artifact> inputs,
-      Root middlemanDir, String tag) {
+      ActionOwner owner,
+      @Nullable Artifact owningArtifact,
+      Iterable<Artifact> inputs,
+      ArtifactRoot middlemanDir,
+      String tag) {
     Preconditions.checkArgument(middlemanDir.isMiddlemanRoot());
     if (hasExactlyOneInput(inputs)) { // Optimization: No middleman for just one input.
       return Iterables.getOnlyElement(inputs);
@@ -114,19 +112,23 @@
    *
    * @param owner the owner of the action that will be created. May not be null.
    * @param middlemanName a unique file name for the middleman artifact in the {@code middlemanDir};
-   *        in practice this is usually the owning rule's label (so it gets escaped as such)
+   *     in practice this is usually the owning rule's label (so it gets escaped as such)
    * @param purpose the purpose for which this middleman is created. This should be a string which
-   *        is suitable for use as a filename. A single rule may have many middlemen with distinct
-   *        purposes.
+   *     is suitable for use as a filename. A single rule may have many middlemen with distinct
+   *     purposes.
    * @param inputs the set of artifacts for which the created artifact is to be the middleman; must
-   *        not be null or empty
+   *     not be null or empty
    * @param middlemanDir the directory in which to place the middleman.
    * @return a middleman that enforces scheduling order (just like a scheduling middleman) and
-   *         propagates errors, but is ignored by the dependency checker
+   *     propagates errors, but is ignored by the dependency checker
    * @throws IllegalArgumentException if {@code inputs} is null or empty
    */
-  public Artifact createErrorPropagatingMiddleman(ActionOwner owner, String middlemanName,
-      String purpose, Iterable<Artifact> inputs, Root middlemanDir) {
+  public Artifact createErrorPropagatingMiddleman(
+      ActionOwner owner,
+      String middlemanName,
+      String purpose,
+      Iterable<Artifact> inputs,
+      ArtifactRoot middlemanDir) {
     Preconditions.checkArgument(inputs != null);
     Preconditions.checkArgument(!Iterables.isEmpty(inputs));
     // We must always create this middleman even if there is only one input.
@@ -135,11 +137,11 @@
   }
 
   /**
-   * Returns the same artifact as {@code createErrorPropagatingMiddleman} would return,
-   * but doesn't create any action.
+   * Returns the same artifact as {@code createErrorPropagatingMiddleman} would return, but doesn't
+   * create any action.
    */
-  public Artifact getErrorPropagatingMiddlemanArtifact(String middlemanName, String purpose,
-      Root middlemanDir) {
+  public Artifact getErrorPropagatingMiddlemanArtifact(
+      String middlemanName, String purpose, ArtifactRoot middlemanDir) {
     return getStampFileArtifact(middlemanName, purpose, middlemanDir);
   }
 
@@ -150,11 +152,15 @@
    * another synchronized method (getArtifact()).
    *
    * @return null iff {@code inputs} is null or empty; the middleman file and the middleman action
-   *         otherwise
+   *     otherwise
    */
   private Pair<Artifact, Action> createMiddleman(
-      ActionOwner owner, String middlemanName, String purpose, Iterable<Artifact> inputs,
-      Root middlemanDir, MiddlemanType middlemanType) {
+      ActionOwner owner,
+      String middlemanName,
+      String purpose,
+      Iterable<Artifact> inputs,
+      ArtifactRoot middlemanDir,
+      MiddlemanType middlemanType) {
     if (inputs == null || CollectionUtils.isEmpty(inputs)) {
       return null;
     }
@@ -175,8 +181,13 @@
    * <p>Note: there's no need to synchronize this method; the only use of a field is via a call to
    * another synchronized method (getArtifact()).
    */
-  public Artifact createMiddlemanAllowMultiple(ActionRegistry registry, ActionOwner owner,
-      PathFragment packageDirectory, String purpose, Iterable<Artifact> inputs, Root middlemanDir) {
+  public Artifact createMiddlemanAllowMultiple(
+      ActionRegistry registry,
+      ActionOwner owner,
+      PathFragment packageDirectory,
+      String purpose,
+      Iterable<Artifact> inputs,
+      ArtifactRoot middlemanDir) {
     String escapedPackageDirectory = Actions.escapedPath(packageDirectory.getPathString());
     PathFragment stampName =
         PathFragment.create("_middlemen/" + (purpose.startsWith(escapedPackageDirectory)
@@ -188,7 +199,8 @@
     return stampFile;
   }
 
-  private Artifact getStampFileArtifact(String middlemanName, String purpose, Root middlemanDir) {
+  private Artifact getStampFileArtifact(
+      String middlemanName, String purpose, ArtifactRoot middlemanDir) {
     String escapedFilename = Actions.escapedPath(middlemanName);
     PathFragment stampName = PathFragment.create("_middlemen/" + escapedFilename + "-" + purpose);
     Artifact stampFile = artifactFactory.getDerivedArtifact(stampName, middlemanDir,

diff --git a/src/main/java/com/google/devtools/build/lib/actions/PackageRootResolver.java b/src/main/java/com/google/devtools/build/lib/actions/PackageRootResolver.java
index 35a795a..e7529bc 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/PackageRootResolver.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/PackageRootResolver.java

@@ -26,13 +26,14 @@
   /**
    * Returns mapping from execPath to Root. Root will be null if the path has no containing package.
    *
-   * @param execPaths the paths to find {@link Root}s for. The search for a containing package will
-   *     start with the path's parent directory, since the path is assumed to be a file.
-   * @return mappings from {@code execPath} to {@link Root}, or null if for some reason we cannot
-   *     determine the result at this time (such as when used within a SkyFunction)
+   * @param execPaths the paths to find {@link ArtifactRoot}s for. The search for a containing
+   *     package will start with the path's parent directory, since the path is assumed to be a
+   *     file.
+   * @return mappings from {@code execPath} to {@link ArtifactRoot}, or null if for some reason we
+   *     cannot determine the result at this time (such as when used within a SkyFunction)
    */
   @Nullable
-  Map<PathFragment, Root> findPackageRootsForFiles(Iterable<PathFragment> execPaths)
+  Map<PathFragment, ArtifactRoot> findPackageRootsForFiles(Iterable<PathFragment> execPaths)
       throws InterruptedException;
 
   /**
@@ -40,13 +41,14 @@
    * Unlike {@link #findPackageRootsForFiles(Iterable)}, this function allows directories in the
    * list of exec paths.
    *
-   * @param execPaths the paths to find {@link Root}s for. The search for a containing package will
-   *     start with the path's parent directory, since the path is assumed to be a file.
-   * @return mappings from {@code execPath} to {@link Root}, or null if for some reason we cannot
-   *     determine the result at this time (such as when used within a SkyFunction)
+   * @param execPaths the paths to find {@link ArtifactRoot}s for. The search for a containing
+   *     package will start with the path's parent directory, since the path is assumed to be a
+   *     file.
+   * @return mappings from {@code execPath} to {@link ArtifactRoot}, or null if for some reason we
+   *     cannot determine the result at this time (such as when used within a SkyFunction)
    */
   // TODO(bazel-team): Remove this once we don't need to find package roots for directories.
   @Nullable
-  Map<PathFragment, Root> findPackageRoots(Iterable<PathFragment> execPaths)
+  Map<PathFragment, ArtifactRoot> findPackageRoots(Iterable<PathFragment> execPaths)
       throws InterruptedException;
 }

diff --git a/src/main/java/com/google/devtools/build/lib/actions/PackageRoots.java b/src/main/java/com/google/devtools/build/lib/actions/PackageRoots.java
index 35f7f3f..9275e3f 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/PackageRoots.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/PackageRoots.java

@@ -39,12 +39,12 @@
   /** Interface for getting the source root of a package, given its {@link PackageIdentifier}. */
   interface PackageRootLookup {
     /**
-     * Returns the {@link Root} of a package, given its {@link PackageIdentifier}. May be null if
-     * the given {@code packageIdentifier} does not correspond to a package in this build. However,
-     * if there is a unique source root for all packages, this may return that root even if the
-     * {@code packageIdentifier} given does not correspond to any packages.
+     * Returns the {@link ArtifactRoot} of a package, given its {@link PackageIdentifier}. May be
+     * null if the given {@code packageIdentifier} does not correspond to a package in this build.
+     * However, if there is a unique source root for all packages, this may return that root even if
+     * the {@code packageIdentifier} given does not correspond to any packages.
      */
     @Nullable
-    Root getRootForPackage(PackageIdentifier packageIdentifier);
+    ArtifactRoot getRootForPackage(PackageIdentifier packageIdentifier);
   }
 }

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/AnalysisEnvironment.java b/src/main/java/com/google/devtools/build/lib/analysis/AnalysisEnvironment.java
index 2d7466d..098a04e 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/AnalysisEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/AnalysisEnvironment.java

@@ -21,8 +21,8 @@
 import com.google.devtools.build.lib.actions.ActionKeyContext;
 import com.google.devtools.build.lib.actions.ActionRegistry;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MiddlemanFactory;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory.BuildInfoKey;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.events.ExtendedEventHandler;
@@ -52,10 +52,11 @@
   /**
    * Returns the artifact for the derived file {@code rootRelativePath}.
    *
-   * <p><b>DO NOT USE</b> in rule implementations. Use
-   * {@link RuleContext#getPackageRelativeArtifact(PathFragment, Root)} or
-   * {@link RuleContext#getUniqueDirectoryArtifact(String, PathFragment, Root)}, or, if there is
-   * really no other way, {@link RuleContext#getShareableArtifact(PathFragment, Root)} instead.
+   * <p><b>DO NOT USE</b> in rule implementations. Use {@link
+   * RuleContext#getPackageRelativeArtifact(PathFragment, ArtifactRoot)} or {@link
+   * RuleContext#getUniqueDirectoryArtifact(String, PathFragment, ArtifactRoot)}, or, if there is
+   * really no other way, {@link RuleContext#getShareableArtifact(PathFragment, ArtifactRoot)}
+   * instead.
    *
    * <p>Creates the artifact if necessary and sets the root of that artifact to {@code root}.
    *
@@ -63,33 +64,32 @@
    * artifacts generated by two different rules to clash. To avoid this, use the artifact creation
    * method on {@link RuleContext} mentioned above.
    */
-  Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root);
+  Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root);
 
   /**
-   * Returns an artifact for the derived file {@code rootRelativePath} whose changes do not cause
-   * a rebuild.
+   * Returns an artifact for the derived file {@code rootRelativePath} whose changes do not cause a
+   * rebuild.
    *
    * <p>Creates the artifact if necessary and sets the root of that artifact to {@code root}.
    *
    * <p>This is useful for files that store data that changes very frequently (e.g. current time)
    * but does not substantially affect the result of the build.
    */
-  Artifact getConstantMetadataArtifact(PathFragment rootRelativePath,
-      Root root);
+  Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, ArtifactRoot root);
 
   /**
    * Returns the artifact for the derived TreeArtifact with directory {@code rootRelativePath},
-   * creating it if necessary, and setting the root of that artifact to
-   * {@code root}. The artifact will be a TreeArtifact.
+   * creating it if necessary, and setting the root of that artifact to {@code root}. The artifact
+   * will be a TreeArtifact.
    */
-  Artifact getTreeArtifact(PathFragment rootRelativePath, Root root);
+  Artifact getTreeArtifact(PathFragment rootRelativePath, ArtifactRoot root);
 
   /**
-   * Returns the artifact for the derived file {@code rootRelativePath},
-   * creating it if necessary, and setting the root of that artifact to
-   * {@code root}. The artifact will represent the output directory of a {@code Fileset}.
+   * Returns the artifact for the derived file {@code rootRelativePath}, creating it if necessary,
+   * and setting the root of that artifact to {@code root}. The artifact will represent the output
+   * directory of a {@code Fileset}.
    */
-  Artifact getFilesetArtifact(PathFragment rootRelativePath, Root root);
+  Artifact getFilesetArtifact(PathFragment rootRelativePath, ArtifactRoot root);
 
   /**
    * Returns the middleman factory associated with the build.

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/BlazeDirectories.java b/src/main/java/com/google/devtools/build/lib/analysis/BlazeDirectories.java
index 3e7df15..bbae6b4 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/BlazeDirectories.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/BlazeDirectories.java

@@ -16,7 +16,7 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.hash.HashCode;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.skyframe.serialization.InjectingObjectCodec;
 import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
@@ -171,8 +171,8 @@
    * Returns the configuration-independent root where the build-data should be placed, given the
    * {@link BlazeDirectories} of this server instance. Nothing else should be placed here.
    */
-  public Root getBuildDataDirectory(String workspaceName) {
-    return Root.asDerivedRoot(getExecRoot(workspaceName), getOutputPath(workspaceName));
+  public ArtifactRoot getBuildDataDirectory(String workspaceName) {
+    return ArtifactRoot.asDerivedRoot(getExecRoot(workspaceName), getOutputPath(workspaceName));
   }
 
   /**

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/CachingAnalysisEnvironment.java b/src/main/java/com/google/devtools/build/lib/analysis/CachingAnalysisEnvironment.java
index 81d5d2e..94cc572 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/CachingAnalysisEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/CachingAnalysisEnvironment.java

@@ -23,8 +23,8 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MiddlemanFactory;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoCollection;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory.BuildInfoKey;
@@ -233,7 +233,7 @@
   }
 
   @Override
-  public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     Preconditions.checkState(enabled);
     return trackArtifactAndOrigin(
         artifactFactory.getDerivedArtifact(rootRelativePath, root, getOwner()),
@@ -241,7 +241,7 @@
   }
 
   @Override
-  public Artifact getTreeArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getTreeArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     Preconditions.checkState(enabled);
     return trackArtifactAndOrigin(
         artifactFactory.getTreeArtifact(rootRelativePath, root, getOwner()),
@@ -249,7 +249,7 @@
   }
 
   @Override
-  public Artifact getFilesetArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getFilesetArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     Preconditions.checkState(enabled);
     return trackArtifactAndOrigin(
         artifactFactory.getFilesetArtifact(rootRelativePath, root, getOwner()),
@@ -257,7 +257,7 @@
   }
 
   @Override
-  public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     return artifactFactory.getConstantMetadataArtifact(rootRelativePath, root, getOwner());
   }
 

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredTargetFactory.java b/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredTargetFactory.java
index 3ad0240..af99802 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredTargetFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredTargetFactory.java

@@ -22,8 +22,8 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.FailAction;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration.Fragment;
 import com.google.devtools.build.lib.analysis.config.ConfigMatchingProvider;
@@ -163,9 +163,10 @@
       BuildConfiguration configuration, boolean isFileset, ArtifactFactory artifactFactory)
       throws InterruptedException {
     Rule rule = outputFile.getAssociatedRule();
-    Root root = rule.hasBinaryOutput()
-        ? configuration.getBinDirectory(rule.getRepository())
-        : configuration.getGenfilesDirectory(rule.getRepository());
+    ArtifactRoot root =
+        rule.hasBinaryOutput()
+            ? configuration.getBinDirectory(rule.getRepository())
+            : configuration.getGenfilesDirectory(rule.getRepository());
     ArtifactOwner owner =
         ConfiguredTargetKey.of(
             rule.getLabel(),
@@ -276,7 +277,7 @@
       Artifact artifact =
           artifactFactory.getSourceArtifact(
               inputFile.getExecPath(),
-              Root.asSourceRoot(inputFile.getPackage().getSourceRoot()),
+              ArtifactRoot.asSourceRoot(inputFile.getPackage().getSourceRoot()),
               ConfiguredTargetKey.of(target.getLabel(), config));
 
       return new InputFileConfiguredTarget(targetContext, inputFile, artifact);

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java b/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
index 2e366d9..674fd55 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java

@@ -37,7 +37,7 @@
 import com.google.devtools.build.lib.actions.ActionRegistry;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider.PrerequisiteValidator;
 import com.google.devtools.build.lib.analysis.actions.ActionConstructionContext;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory.BuildInfoKey;
@@ -269,12 +269,12 @@
   }
 
   @Override
-  public Root getBinDirectory() {
+  public ArtifactRoot getBinDirectory() {
     return getConfiguration().getBinDirectory(rule.getRepository());
   }
 
   @Override
-  public Root getMiddlemanDirectory() {
+  public ArtifactRoot getMiddlemanDirectory() {
     return getConfiguration().getMiddlemanDirectory(rule.getRepository());
   }
 
@@ -565,27 +565,26 @@
         target.getLabel().getPackageIdentifier().equals(getLabel().getPackageIdentifier()),
         "Creating output artifact for target '%s' in different package than the rule '%s' "
             + "being analyzed", target.getLabel(), getLabel());
-    Root root = getBinOrGenfilesDirectory();
+    ArtifactRoot root = getBinOrGenfilesDirectory();
     return getPackageRelativeArtifact(target.getName(), root);
   }
 
   /**
-   * Returns the root of either the "bin" or "genfiles"
-   * tree, based on this target and the current configuration.
-   * The choice of which tree to use is based on the rule with
-   * which this target (which must be an OutputFile or a Rule) is associated.
+   * Returns the root of either the "bin" or "genfiles" tree, based on this target and the current
+   * configuration. The choice of which tree to use is based on the rule with which this target
+   * (which must be an OutputFile or a Rule) is associated.
    */
-  public Root getBinOrGenfilesDirectory() {
+  public ArtifactRoot getBinOrGenfilesDirectory() {
     return rule.hasBinaryOutput()
         ? getConfiguration().getBinDirectory(rule.getRepository())
         : getConfiguration().getGenfilesDirectory(rule.getRepository());
   }
 
   /**
-   * Creates an artifact in a directory that is unique to the package that contains the rule,
-   * thus guaranteeing that it never clashes with artifacts created by rules in other packages.
+   * Creates an artifact in a directory that is unique to the package that contains the rule, thus
+   * guaranteeing that it never clashes with artifacts created by rules in other packages.
    */
-  public Artifact getPackageRelativeArtifact(String relative, Root root) {
+  public Artifact getPackageRelativeArtifact(String relative, ArtifactRoot root) {
     return getPackageRelativeArtifact(PathFragment.create(relative), root);
   }
 
@@ -620,18 +619,18 @@
    * option.
    *
    * <p>This artifact can be created anywhere in the output tree, which, in addition to making
-   * sharing possible, opens up the possibility of action conflicts and makes it impossible to
-   * infer the label of the rule creating the artifact from the path of the artifact.
+   * sharing possible, opens up the possibility of action conflicts and makes it impossible to infer
+   * the label of the rule creating the artifact from the path of the artifact.
    */
-  public Artifact getShareableArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getShareableArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     return getAnalysisEnvironment().getDerivedArtifact(rootRelativePath, root);
   }
 
   /**
-   * Creates an artifact in a directory that is unique to the package that contains the rule,
-   * thus guaranteeing that it never clashes with artifacts created by rules in other packages.
+   * Creates an artifact in a directory that is unique to the package that contains the rule, thus
+   * guaranteeing that it never clashes with artifacts created by rules in other packages.
    */
-  public Artifact getPackageRelativeArtifact(PathFragment relative, Root root) {
+  public Artifact getPackageRelativeArtifact(PathFragment relative, ArtifactRoot root) {
     return getDerivedArtifact(getPackageDirectory().getRelative(relative), root);
   }
 
@@ -639,15 +638,16 @@
    * Returns the root-relative path fragment under which output artifacts of this rule should go.
    *
    * <p>Note that:
+   *
    * <ul>
    *   <li>This doesn't guarantee that there are no clashes with rules in the same package.
-   *   <li>If possible, {@link #getPackageRelativeArtifact(PathFragment, Root)} should be used
-   *   instead of this method.
+   *   <li>If possible, {@link #getPackageRelativeArtifact(PathFragment, ArtifactRoot)} should be
+   *       used instead of this method.
    * </ul>
    *
    * Ideally, user-visible artifacts should all have corresponding output file targets, all others
-   * should go into a rule-specific directory.
-   * {@link #getUniqueDirectoryArtifact(String, PathFragment, Root)}) ensures that this is the case.
+   * should go into a rule-specific directory. {@link #getUniqueDirectoryArtifact(String,
+   * PathFragment, ArtifactRoot)}) ensures that this is the case.
    */
   public PathFragment getPackageDirectory() {
     return getLabel().getPackageIdentifier().getSourceRoot();
@@ -661,7 +661,7 @@
    * method.
    */
   @Override
-  public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     Preconditions.checkState(rootRelativePath.startsWith(getPackageDirectory()),
         "Output artifact '%s' not under package directory '%s' for target '%s'",
         rootRelativePath, getPackageDirectory(), getLabel());
@@ -675,7 +675,7 @@
    * thus ensuring that it doesn't clash with other artifacts generated by other rules using this
    * method.
    */
-  public Artifact getTreeArtifact(PathFragment rootRelativePath, Root root) {
+  public Artifact getTreeArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     Preconditions.checkState(rootRelativePath.startsWith(getPackageDirectory()),
         "Output artifact '%s' not under package directory '%s' for target '%s'",
         rootRelativePath, getPackageDirectory(), getLabel());
@@ -686,7 +686,7 @@
    * Creates a tree artifact in a directory that is unique to the package that contains the rule,
    * thus guaranteeing that it never clashes with artifacts created by rules in other packages.
    */
-  public Artifact getPackageRelativeTreeArtifact(PathFragment relative, Root root) {
+  public Artifact getPackageRelativeTreeArtifact(PathFragment relative, ArtifactRoot root) {
     return getTreeArtifact(getPackageDirectory().getRelative(relative), root);
   }
 
@@ -695,7 +695,7 @@
    * clashes with artifacts created by other rules.
    */
   public Artifact getUniqueDirectoryArtifact(
-      String uniqueDirectory, String relative, Root root) {
+      String uniqueDirectory, String relative, ArtifactRoot root) {
     return getUniqueDirectoryArtifact(uniqueDirectory, PathFragment.create(relative), root);
   }
 
@@ -704,7 +704,7 @@
    * clashes with artifacts created by other rules.
    */
   public Artifact getUniqueDirectoryArtifact(
-      String uniqueDirectory, PathFragment relative, Root root) {
+      String uniqueDirectory, PathFragment relative, ArtifactRoot root) {
     return getDerivedArtifact(getUniqueDirectory(uniqueDirectory).getRelative(relative), root);
   }
 

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/SkyframePackageRootResolver.java b/src/main/java/com/google/devtools/build/lib/analysis/SkyframePackageRootResolver.java
index 9a9eee3..082c122 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/SkyframePackageRootResolver.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/SkyframePackageRootResolver.java

@@ -14,8 +14,8 @@
 
 package com.google.devtools.build.lib.analysis;
 
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.PackageRootResolver;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.events.ExtendedEventHandler;
 import com.google.devtools.build.lib.skyframe.SkyframeExecutor;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -37,14 +37,14 @@
   }
 
   @Override
-  public Map<PathFragment, Root> findPackageRootsForFiles(Iterable<PathFragment> execPaths)
+  public Map<PathFragment, ArtifactRoot> findPackageRootsForFiles(Iterable<PathFragment> execPaths)
       throws InterruptedException {
     return executor.getArtifactRootsForFiles(eventHandler, execPaths);
   }
-  
+
   @Override
   @Nullable
-  public Map<PathFragment, Root> findPackageRoots(Iterable<PathFragment> execPaths)
+  public Map<PathFragment, ArtifactRoot> findPackageRoots(Iterable<PathFragment> execPaths)
       throws InterruptedException {
     return executor.getArtifactRoots(eventHandler, execPaths);
   }

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/actions/ActionConstructionContext.java b/src/main/java/com/google/devtools/build/lib/analysis/actions/ActionConstructionContext.java
index 3b10c5a..1eefb53 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/actions/ActionConstructionContext.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/actions/ActionConstructionContext.java

@@ -15,7 +15,7 @@
 
 import com.google.devtools.build.lib.actions.ActionOwner;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.AnalysisEnvironment;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.analysis.platform.PlatformInfo;
@@ -28,15 +28,11 @@
  */
 public interface ActionConstructionContext {
 
-  /**
-   * Returns the bin directory for constructed actions.
-   */
-  Root getBinDirectory();
+  /** Returns the bin directory for constructed actions. */
+  ArtifactRoot getBinDirectory();
 
-  /**
-   * Returns the internal directory (used for middlemen) for constructed actions.
-   */
-  Root getMiddlemanDirectory();
+  /** Returns the internal directory (used for middlemen) for constructed actions. */
+  ArtifactRoot getMiddlemanDirectory();
 
   /** Returns the action owner that should be used for actions. */
   ActionOwner getActionOwner();
@@ -54,7 +50,7 @@
    * thus ensuring that it doesn't clash with other artifacts generated by other rules using this
    * method.
    */
-  Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root);
+  Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root);
 
   /** Returns the {@link PlatformInfo} describing the execution platform this action should use. */
   @Nullable

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/buildinfo/BuildInfoFactory.java b/src/main/java/com/google/devtools/build/lib/analysis/buildinfo/BuildInfoFactory.java
index 07e9918..468fb27 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/buildinfo/BuildInfoFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/buildinfo/BuildInfoFactory.java

@@ -14,11 +14,10 @@
 package com.google.devtools.build.lib.analysis.buildinfo;
 
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.vfs.PathFragment;
-
 import java.io.Serializable;
 
 /**
@@ -47,7 +46,8 @@
    * Context for the creation of build-info artifacts.
    */
   interface BuildInfoContext {
-    Artifact getBuildInfoArtifact(PathFragment rootRelativePath, Root root, BuildInfoType type);
+    Artifact getBuildInfoArtifact(
+        PathFragment rootRelativePath, ArtifactRoot root, BuildInfoType type);
   }
 
   /**

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
index 9b6f5d1..10daadd 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java

@@ -34,7 +34,7 @@
 import com.google.common.collect.Multimap;
 import com.google.common.collect.MutableClassToInstanceMap;
 import com.google.devtools.build.lib.actions.ActionEnvironment;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
 import com.google.devtools.build.lib.analysis.RuleContext;
@@ -1185,8 +1185,10 @@
       this.middleman = false;
     }
 
-    Root getRoot(
-        RepositoryName repositoryName, String outputDirName, BlazeDirectories directories,
+    ArtifactRoot getRoot(
+        RepositoryName repositoryName,
+        String outputDirName,
+        BlazeDirectories directories,
         RepositoryName mainRepositoryName) {
       // e.g., execroot/repo1
       Path execRoot = directories.getExecRoot(mainRepositoryName.strippedName());
@@ -1194,10 +1196,11 @@
       Path outputDir = execRoot.getRelative(directories.getRelativeOutputPath())
           .getRelative(outputDirName);
       if (middleman) {
-        return INTERNER.intern(Root.middlemanRoot(execRoot, outputDir));
+        return INTERNER.intern(ArtifactRoot.middlemanRoot(execRoot, outputDir));
       }
       // e.g., [[execroot/repo1]/bazel-out/config/bin]
-      return INTERNER.intern(Root.asDerivedRoot(execRoot, outputDir.getRelative(nameFragment)));
+      return INTERNER.intern(
+          ArtifactRoot.asDerivedRoot(execRoot, outputDir.getRelative(nameFragment)));
     }
   }
 
@@ -1206,16 +1209,16 @@
 
   // We intern the roots for non-main repositories, so we don't keep around thousands of copies of
   // the same root.
-  private static Interner<Root> INTERNER = Interners.newWeakInterner();
+  private static Interner<ArtifactRoot> INTERNER = Interners.newWeakInterner();
 
   // We precompute the roots for the main repository, since that's the common case.
-  private final Root outputDirectoryForMainRepository;
-  private final Root binDirectoryForMainRepository;
-  private final Root includeDirectoryForMainRepository;
-  private final Root genfilesDirectoryForMainRepository;
-  private final Root coverageDirectoryForMainRepository;
-  private final Root testlogsDirectoryForMainRepository;
-  private final Root middlemanDirectoryForMainRepository;
+  private final ArtifactRoot outputDirectoryForMainRepository;
+  private final ArtifactRoot binDirectoryForMainRepository;
+  private final ArtifactRoot includeDirectoryForMainRepository;
+  private final ArtifactRoot genfilesDirectoryForMainRepository;
+  private final ArtifactRoot coverageDirectoryForMainRepository;
+  private final ArtifactRoot testlogsDirectoryForMainRepository;
+  private final ArtifactRoot middlemanDirectoryForMainRepository;
 
   private final boolean separateGenfilesDirectory;
 
@@ -1575,22 +1578,18 @@
     return platformName;
   }
 
-  /**
-   * Returns the output directory for this build configuration.
-   */
-  public Root getOutputDirectory(RepositoryName repositoryName) {
+  /** Returns the output directory for this build configuration. */
+  public ArtifactRoot getOutputDirectory(RepositoryName repositoryName) {
     return repositoryName.isMain() || repositoryName.equals(mainRepositoryName)
         ? outputDirectoryForMainRepository
         : OutputDirectory.OUTPUT.getRoot(
             repositoryName, outputDirName, directories, mainRepositoryName);
   }
 
-  /**
-   * Returns the bin directory for this build configuration.
-   */
+  /** Returns the bin directory for this build configuration. */
   @SkylarkCallable(name = "bin_dir", structField = true, documented = false)
   @Deprecated
-  public Root getBinDirectory() {
+  public ArtifactRoot getBinDirectory() {
     return getBinDirectory(RepositoryName.MAIN);
   }
 
@@ -1600,7 +1599,7 @@
    * issue right now because it only effects Blaze's include scanning (internal) and Bazel's
    * repositories (external) but will need to be fixed.
    */
-  public Root getBinDirectory(RepositoryName repositoryName) {
+  public ArtifactRoot getBinDirectory(RepositoryName repositoryName) {
     return repositoryName.isMain() || repositoryName.equals(mainRepositoryName)
         ? binDirectoryForMainRepository
         : OutputDirectory.BIN.getRoot(
@@ -1614,26 +1613,22 @@
     return getBinDirectory().getExecPath();
   }
 
-  /**
-   * Returns the include directory for this build configuration.
-   */
-  public Root getIncludeDirectory(RepositoryName repositoryName) {
+  /** Returns the include directory for this build configuration. */
+  public ArtifactRoot getIncludeDirectory(RepositoryName repositoryName) {
     return repositoryName.isMain() || repositoryName.equals(mainRepositoryName)
         ? includeDirectoryForMainRepository
         : OutputDirectory.INCLUDE.getRoot(
             repositoryName, outputDirName, directories, mainRepositoryName);
   }
 
-  /**
-   * Returns the genfiles directory for this build configuration.
-   */
+  /** Returns the genfiles directory for this build configuration. */
   @SkylarkCallable(name = "genfiles_dir", structField = true, documented = false)
   @Deprecated
-  public Root getGenfilesDirectory() {
+  public ArtifactRoot getGenfilesDirectory() {
     return getGenfilesDirectory(RepositoryName.MAIN);
   }
 
-  public Root getGenfilesDirectory(RepositoryName repositoryName) {
+  public ArtifactRoot getGenfilesDirectory(RepositoryName repositoryName) {
     if (!separateGenfilesDirectory) {
       return getBinDirectory(repositoryName);
     }
@@ -1645,21 +1640,19 @@
   }
 
   /**
-   * Returns the directory where coverage-related artifacts and metadata files
-   * should be stored. This includes for example uninstrumented class files
-   * needed for Jacoco's coverage reporting tools.
+   * Returns the directory where coverage-related artifacts and metadata files should be stored.
+   * This includes for example uninstrumented class files needed for Jacoco's coverage reporting
+   * tools.
    */
-  public Root getCoverageMetadataDirectory(RepositoryName repositoryName) {
+  public ArtifactRoot getCoverageMetadataDirectory(RepositoryName repositoryName) {
     return repositoryName.isMain() || repositoryName.equals(mainRepositoryName)
         ? coverageDirectoryForMainRepository
         : OutputDirectory.COVERAGE.getRoot(
             repositoryName, outputDirName, directories, mainRepositoryName);
   }
 
-  /**
-   * Returns the testlogs directory for this build configuration.
-   */
-  public Root getTestLogsDirectory(RepositoryName repositoryName) {
+  /** Returns the testlogs directory for this build configuration. */
+  public ArtifactRoot getTestLogsDirectory(RepositoryName repositoryName) {
     return repositoryName.isMain() || repositoryName.equals(mainRepositoryName)
         ? testlogsDirectoryForMainRepository
         : OutputDirectory.TESTLOGS.getRoot(
@@ -1686,10 +1679,8 @@
     return OS.getCurrent() == OS.WINDOWS ? ";" : ":";
   }
 
-  /**
-   * Returns the internal directory (used for middlemen) for this build configuration.
-   */
-  public Root getMiddlemanDirectory(RepositoryName repositoryName) {
+  /** Returns the internal directory (used for middlemen) for this build configuration. */
+  public ArtifactRoot getMiddlemanDirectory(RepositoryName repositoryName) {
     return repositoryName.isMain() || repositoryName.equals(mainRepositoryName)
         ? middlemanDirectoryForMainRepository
         : OutputDirectory.MIDDLEMAN.getRoot(

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkActionFactory.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkActionFactory.java
index e77b159..4bf9999 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkActionFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkActionFactory.java

@@ -18,8 +18,8 @@
 import com.google.devtools.build.lib.actions.Action;
 import com.google.devtools.build.lib.actions.ActionAnalysisMetadata;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.ParameterFile.ParameterFileType;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.actions.extra.SpawnInfo;
 import com.google.devtools.build.lib.analysis.CommandHelper;
@@ -94,7 +94,7 @@
     this.ruleContext = ruleContext;
   }
 
-  Root newFileRoot() throws EvalException {
+  ArtifactRoot newFileRoot() throws EvalException {
     return context.isForAspect()
         ? ruleContext.getConfiguration().getBinDirectory(ruleContext.getRule().getRepository())
         : ruleContext.getBinOrGenfilesDirectory();

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleContext.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleContext.java
index 3dbb8d9..de2bd46 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleContext.java

@@ -25,7 +25,7 @@
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Ordering;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.ActionsProvider;
 import com.google.devtools.build.lib.analysis.ConfigurationMakeVariableContext;
 import com.google.devtools.build.lib.analysis.DefaultInfo;
@@ -708,16 +708,22 @@
     return ImmutableList.copyOf(ruleContext.getFeatures());
   }
 
-  @SkylarkCallable(name = "bin_dir", structField = true,
-      doc = "The root corresponding to bin directory.")
-  public Root getBinDirectory() throws EvalException {
+  @SkylarkCallable(
+    name = "bin_dir",
+    structField = true,
+    doc = "The root corresponding to bin directory."
+  )
+  public ArtifactRoot getBinDirectory() throws EvalException {
     checkMutable("bin_dir");
     return getConfiguration().getBinDirectory(ruleContext.getRule().getRepository());
   }
 
-  @SkylarkCallable(name = "genfiles_dir", structField = true,
-      doc = "The root corresponding to genfiles directory.")
-  public Root getGenfilesDirectory() throws EvalException {
+  @SkylarkCallable(
+    name = "genfiles_dir",
+    structField = true,
+    doc = "The root corresponding to genfiles directory."
+  )
+  public ArtifactRoot getGenfilesDirectory() throws EvalException {
     checkMutable("genfiles_dir");
     return getConfiguration().getGenfilesDirectory(ruleContext.getRule().getRepository());
   }
@@ -845,7 +851,7 @@
 
   // Kept for compatibility with old code.
   @SkylarkCallable(documented = false)
-  public Artifact newFile(Root root, String filename) throws EvalException {
+  public Artifact newFile(ArtifactRoot root, String filename) throws EvalException {
     checkMutable("new_file");
     return ruleContext.getPackageRelativeArtifact(filename, root);
   }
@@ -877,7 +883,8 @@
 
   // Kept for compatibility with old code.
   @SkylarkCallable(documented = false)
-  public Artifact newFile(Root root, Artifact baseArtifact, String suffix) throws EvalException {
+  public Artifact newFile(ArtifactRoot root, Artifact baseArtifact, String suffix)
+      throws EvalException {
     checkMutable("new_file");
     PathFragment original = baseArtifact.getRootRelativePath();
     PathFragment fragment = original.replaceName(original.getBaseName() + suffix);

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java b/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java
index 81d6993..37cfbbe 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java

@@ -21,7 +21,7 @@
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.AnalysisEnvironment;
 import com.google.devtools.build.lib.analysis.FileProvider;
 import com.google.devtools.build.lib.analysis.FilesToRunProvider;
@@ -187,7 +187,7 @@
     PathFragment targetName = PathFragment.create(ruleContext.getLabel().getName());
     BuildConfiguration config = ruleContext.getConfiguration();
     AnalysisEnvironment env = ruleContext.getAnalysisEnvironment();
-    Root root = config.getTestLogsDirectory(ruleContext.getRule().getRepository());
+    ArtifactRoot root = config.getTestLogsDirectory(ruleContext.getRule().getRepository());
 
     NestedSetBuilder<Artifact> inputsBuilder = NestedSetBuilder.stableOrder();
     inputsBuilder.addTransitive(

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/BazelWorkspaceStatusModule.java b/src/main/java/com/google/devtools/build/lib/bazel/BazelWorkspaceStatusModule.java
index e3e405b..1fd392d 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/BazelWorkspaceStatusModule.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/BazelWorkspaceStatusModule.java

@@ -30,8 +30,8 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.ExecutionStrategy;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.BuildInfo;
 import com.google.devtools.build.lib.analysis.BuildInfoEvent;
@@ -304,7 +304,7 @@
     public WorkspaceStatusAction createWorkspaceStatusAction(
         ArtifactFactory factory, ArtifactOwner artifactOwner, Supplier<UUID> buildId,
         String workspaceName) {
-      Root root = env.getDirectories().getBuildDataDirectory(workspaceName);
+      ArtifactRoot root = env.getDirectories().getBuildDataDirectory(workspaceName);
 
       Artifact stableArtifact = factory.getDerivedArtifact(
           PathFragment.create("stable-status.txt"), root, artifactOwner);

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcIncLibrary.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcIncLibrary.java
index c1a40fc..a459e42 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcIncLibrary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcIncLibrary.java

@@ -17,7 +17,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
@@ -85,7 +85,7 @@
     // is actually a symlink into the source tree.
     PathFragment includeDirectory = PathFragment.create("_")
         .getRelative(ruleContext.getTarget().getName());
-    Root configIncludeDirectory =
+    ArtifactRoot configIncludeDirectory =
         ruleContext.getConfiguration().getIncludeDirectory(ruleContext.getRule().getRepository());
     PathFragment includePath =
         configIncludeDirectory

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppBuildInfo.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppBuildInfo.java
index 8e49f99..1c68580 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppBuildInfo.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppBuildInfo.java

@@ -16,13 +16,12 @@
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.actions.Action;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoCollection;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.vfs.PathFragment;
-
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -69,7 +68,7 @@
       BuildConfiguration config, PathFragment headerName,
       Collection<Artifact> inputs,
       boolean writeVolatileInfo, boolean writeNonVolatileInfo, RepositoryName repositoryName) {
-    Root outputPath = config.getIncludeDirectory(repositoryName);
+    ArtifactRoot outputPath = config.getIncludeDirectory(repositoryName);
     final Artifact header =
         buildInfoContext.getBuildInfoArtifact(headerName, outputPath,
             writeVolatileInfo && !inputs.isEmpty()

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java
index 738cc98..8edc2d9 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java

@@ -26,7 +26,7 @@
 import com.google.common.collect.Iterables;
 import com.google.common.io.ByteSource;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.AnalysisEnvironment;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.cmdline.Label;
@@ -172,14 +172,13 @@
   private final Path fdoProfile;
 
   /**
-   * Temporary directory to which the coverage ZIP file is extracted to
-   * (relative to the exec root), or {@code null} if FDO optimization is
-   * disabled. This is used to create artifacts for the extracted files.
+   * Temporary directory to which the coverage ZIP file is extracted to (relative to the exec root),
+   * or {@code null} if FDO optimization is disabled. This is used to create artifacts for the
+   * extracted files.
    *
-   * <p>Note that this root is intentionally not registered with the artifact
-   * factory.
+   * <p>Note that this root is intentionally not registered with the artifact factory.
    */
-  private final Root fdoRoot;
+  private final ArtifactRoot fdoRoot;
 
   /**
    * The relative path of the FDO root to the exec root.
@@ -227,8 +226,14 @@
    * @param fdoProfile path to the profile file passed to --fdo_optimize option
    * @param lipoMode value of the --lipo_mode option
    */
-  private FdoSupport(FdoMode fdoMode, LipoMode lipoMode, Root fdoRoot, PathFragment fdoRootExecPath,
-      PathFragment fdoInstrument, Path fdoProfile, FdoZipContents fdoZipContents) {
+  private FdoSupport(
+      FdoMode fdoMode,
+      LipoMode lipoMode,
+      ArtifactRoot fdoRoot,
+      PathFragment fdoRootExecPath,
+      PathFragment fdoInstrument,
+      Path fdoProfile,
+      FdoZipContents fdoZipContents) {
     this.fdoInstrument = fdoInstrument;
     this.fdoProfile = fdoProfile;
     this.fdoRoot = fdoRoot;
@@ -248,7 +253,7 @@
     }
   }
 
-  public Root getFdoRoot() {
+  public ArtifactRoot getFdoRoot() {
     return fdoRoot;
   }
 
@@ -281,10 +286,10 @@
       lipoMode = LipoMode.OFF;
     }
 
-    Root fdoRoot =
+    ArtifactRoot fdoRoot =
         (fdoProfile == null)
             ? null
-            : Root.asDerivedRoot(execRoot, execRoot.getRelative(productName + "-fdo"));
+            : ArtifactRoot.asDerivedRoot(execRoot, execRoot.getRelative(productName + "-fdo"));
 
     PathFragment fdoRootExecPath = fdoProfile == null
         ? null

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/SolibSymlinkAction.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/SolibSymlinkAction.java
index 7f14ee2..7d60680 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/SolibSymlinkAction.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/SolibSymlinkAction.java

@@ -25,7 +25,7 @@
 import com.google.devtools.build.lib.actions.ActionResult;
 import com.google.devtools.build.lib.actions.Actions;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
@@ -149,7 +149,7 @@
     Preconditions.checkArgument(!library.getRootRelativePath().getSegment(0).startsWith("_solib_"));
 
     // Ignore libraries that are already represented by the symlinks.
-    Root root = configuration.getBinDirectory(ruleContext.getRule().getRepository());
+    ArtifactRoot root = configuration.getBinDirectory(ruleContext.getRule().getRepository());
     Artifact symlink = ruleContext.getShareableArtifact(symlinkName, root);
     ruleContext.registerAction(
         new SolibSymlinkAction(ruleContext.getActionOwner(), library, symlink));

diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaBuildInfoFactory.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaBuildInfoFactory.java
index be7abfb..c372146 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaBuildInfoFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaBuildInfoFactory.java

@@ -17,7 +17,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.actions.Action;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoCollection;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
@@ -126,7 +126,7 @@
       boolean includeVolatile,
       boolean includeNonVolatile,
       RepositoryName repositoryName) {
-    Root outputPath = config.getIncludeDirectory(repositoryName);
+    ArtifactRoot outputPath = config.getIncludeDirectory(repositoryName);
     final Artifact output = context.getBuildInfoArtifact(propertyFileName, outputPath,
         includeVolatile && !inputs.isEmpty() ? BuildInfoType.NO_REBUILD
             : BuildInfoType.FORCE_REBUILD_IF_CHANGED);

diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileAction.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileAction.java
index 62bce38..7bc087b 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileAction.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileAction.java

@@ -32,10 +32,10 @@
 import com.google.devtools.build.lib.actions.ActionOwner;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.CommandLineExpansionException;
 import com.google.devtools.build.lib.actions.ParameterFile;
 import com.google.devtools.build.lib.actions.ResourceSet;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.actions.extra.ExtraActionInfo;
 import com.google.devtools.build.lib.actions.extra.JavaCompileInfo;
@@ -474,17 +474,15 @@
    */
   public interface ArtifactFactory {
 
-    /**
-     * Create an artifact with the specified root-relative path under the specified root.
-     */
-    Artifact create(PathFragment rootRelativePath, Root root);
+    /** Create an artifact with the specified root-relative path under the specified root. */
+    Artifact create(PathFragment rootRelativePath, ArtifactRoot root);
   }
 
   @VisibleForTesting
   static ArtifactFactory createArtifactFactory(final AnalysisEnvironment env) {
     return new ArtifactFactory() {
       @Override
-      public Artifact create(PathFragment rootRelativePath, Root root) {
+      public Artifact create(PathFragment rootRelativePath, ArtifactRoot root) {
         return env.getDerivedArtifact(rootRelativePath, root);
       }
     };
@@ -557,15 +555,17 @@
      * Creates a Builder from an owner and a build configuration.
      */
     public Builder(final RuleContext ruleContext, JavaSemantics semantics) {
-      this(ruleContext.getActionOwner(),
+      this(
+          ruleContext.getActionOwner(),
           ruleContext.getAnalysisEnvironment(),
           new ArtifactFactory() {
             @Override
-            public Artifact create(PathFragment rootRelativePath, Root root) {
+            public Artifact create(PathFragment rootRelativePath, ArtifactRoot root) {
               return ruleContext.getDerivedArtifact(rootRelativePath, root);
             }
           },
-          ruleContext.getConfiguration(), semantics);
+          ruleContext.getConfiguration(),
+          semantics);
     }
 
     public JavaCompileAction build() {

diff --git a/src/main/java/com/google/devtools/build/lib/rules/nativedeps/NativeDepsHelper.java b/src/main/java/com/google/devtools/build/lib/rules/nativedeps/NativeDepsHelper.java
index 55a8efe..7f6437e 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/nativedeps/NativeDepsHelper.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/nativedeps/NativeDepsHelper.java

@@ -19,7 +19,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.actions.SymlinkAction;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
@@ -175,7 +175,7 @@
       CcToolchainProvider toolchain,
       Artifact nativeDeps,
       String libraryIdentifier,
-      Root bindirIfShared,
+      ArtifactRoot bindirIfShared,
       boolean useDynamicRuntime,
       CppSemantics cppSemantics)
       throws InterruptedException {

diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/IntermediateArtifacts.java b/src/main/java/com/google/devtools/build/lib/rules/objc/IntermediateArtifacts.java
index 459de19..4619758 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/IntermediateArtifacts.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/IntermediateArtifacts.java

@@ -17,7 +17,7 @@
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.cmdline.Label;
@@ -244,7 +244,7 @@
   }
 
   private Artifact scopedArtifact(PathFragment scopeRelative, boolean inGenfiles) {
-    Root root =
+    ArtifactRoot root =
         inGenfiles
             ? buildConfiguration.getGenfilesDirectory(ruleContext.getRule().getRepository())
             : buildConfiguration.getBinDirectory(ruleContext.getRule().getRepository());

diff --git a/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoCommon.java b/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoCommon.java
index 3d2d555..a09a9af 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoCommon.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoCommon.java

@@ -20,7 +20,7 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.Runfiles;
 import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
@@ -142,8 +142,8 @@
   public static ImmutableList<Artifact> getGeneratedOutputs(RuleContext ruleContext,
       ImmutableList<Artifact> protoSources, String extension, boolean pythonNames) {
     ImmutableList.Builder<Artifact> outputsBuilder = new ImmutableList.Builder<>();
-    Root genfiles = ruleContext.getConfiguration().getGenfilesDirectory(
-        ruleContext.getRule().getRepository());
+    ArtifactRoot genfiles =
+        ruleContext.getConfiguration().getGenfilesDirectory(ruleContext.getRule().getRepository());
     for (Artifact src : protoSources) {
       PathFragment srcPath = src.getRootRelativePath();
       if (pythonNames) {

diff --git a/src/main/java/com/google/devtools/build/lib/rules/python/PythonUtils.java b/src/main/java/com/google/devtools/build/lib/rules/python/PythonUtils.java
index c44e46e..d76b55b 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/python/PythonUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/python/PythonUtils.java

@@ -15,7 +15,7 @@
 
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.FilesToRunProvider;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.Runfiles;
@@ -82,8 +82,8 @@
    * subdirectory to avoid conflicts (eg. when the input file is generated).
    */
   private static Artifact get2to3OutputArtifact(RuleContext ruleContext, Artifact input) {
-    Root root = ruleContext.getConfiguration().getGenfilesDirectory(
-        ruleContext.getRule().getRepository());
+    ArtifactRoot root =
+        ruleContext.getConfiguration().getGenfilesDirectory(ruleContext.getRule().getRepository());
     PathFragment path = PathFragment.create("python3").getRelative(input.getRootRelativePath());
     return ruleContext.getShareableArtifact(path, root);
   }

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java
index 4643235..52b9b26 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java

@@ -29,10 +29,10 @@
 import com.google.devtools.build.lib.actions.ActionLookupValue;
 import com.google.devtools.build.lib.actions.AlreadyReportedActionExecutionException;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MissingInputFileException;
 import com.google.devtools.build.lib.actions.NotifyOnActionCacheHit;
 import com.google.devtools.build.lib.actions.PackageRootResolver;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.causes.Cause;
 import com.google.devtools.build.lib.causes.LabelCause;
 import com.google.devtools.build.lib.clock.BlazeClock;
@@ -288,8 +288,8 @@
     }
 
     @Override
-    public Map<PathFragment, Root> findPackageRootsForFiles(Iterable<PathFragment> execPaths)
-        throws InterruptedException {
+    public Map<PathFragment, ArtifactRoot> findPackageRootsForFiles(
+        Iterable<PathFragment> execPaths) throws InterruptedException {
       Preconditions.checkState(keysRequested.isEmpty(),
           "resolver should only be called once: %s %s", keysRequested, execPaths);
       // Create SkyKeys list based on execPaths.
@@ -318,7 +318,7 @@
         return null;
       }
 
-      Map<PathFragment, Root> result = new HashMap<>();
+      Map<PathFragment, ArtifactRoot> result = new HashMap<>();
       for (PathFragment path : execPaths) {
         if (!depKeys.containsKey(path)) {
           continue;
@@ -327,8 +327,9 @@
             (ContainingPackageLookupValue) values.get(depKeys.get(path));
         if (value.hasContainingPackage()) {
           // We have found corresponding root for current execPath.
-          result.put(path,
-              Root.computeSourceRoot(
+          result.put(
+              path,
+              ArtifactRoot.computeSourceRoot(
                   value.getContainingPackageRoot(),
                   value.getContainingPackageName().getRepository()));
         } else {
@@ -341,7 +342,7 @@
 
     @Override
     @Nullable
-    public Map<PathFragment, Root> findPackageRoots(Iterable<PathFragment> execPaths)
+    public Map<PathFragment, ArtifactRoot> findPackageRoots(Iterable<PathFragment> execPaths)
         throws InterruptedException {
       // call sites for this implementation of PackageRootResolver shouldn't be passing in
       // directories.

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/BuildInfoCollectionFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/BuildInfoCollectionFunction.java
index c80875d..b8cbd4a 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/BuildInfoCollectionFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/BuildInfoCollectionFunction.java

@@ -19,7 +19,7 @@
 import com.google.devtools.build.lib.actions.ActionKeyContext;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory.BuildInfoContext;
 import com.google.devtools.build.lib.analysis.buildinfo.BuildInfoFactory.BuildInfoKey;
@@ -70,15 +70,16 @@
         nameValue.getName());
 
     final ArtifactFactory factory = artifactFactory.get();
-    BuildInfoContext context = new BuildInfoContext() {
-      @Override
-      public Artifact getBuildInfoArtifact(PathFragment rootRelativePath, Root root,
-          BuildInfoType type) {
-        return type == BuildInfoType.NO_REBUILD
-            ? factory.getConstantMetadataArtifact(rootRelativePath, root, keyAndConfig)
-            : factory.getDerivedArtifact(rootRelativePath, root, keyAndConfig);
-      }
-    };
+    BuildInfoContext context =
+        new BuildInfoContext() {
+          @Override
+          public Artifact getBuildInfoArtifact(
+              PathFragment rootRelativePath, ArtifactRoot root, BuildInfoType type) {
+            return type == BuildInfoType.NO_REBUILD
+                ? factory.getConstantMetadataArtifact(rootRelativePath, root, keyAndConfig)
+                : factory.getDerivedArtifact(rootRelativePath, root, keyAndConfig);
+          }
+        };
 
     return new BuildInfoCollectionValue(
         actionKeyContext,

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/MapAsPackageRoots.java b/src/main/java/com/google/devtools/build/lib/skyframe/MapAsPackageRoots.java
index f969c02..f4ac69f 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/MapAsPackageRoots.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/MapAsPackageRoots.java

@@ -15,8 +15,8 @@
 package com.google.devtools.build.lib.skyframe;
 
 import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.PackageRoots;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.vfs.Path;
 import java.util.HashMap;
@@ -41,12 +41,12 @@
 
   @Override
   public PackageRootLookup getPackageRootLookup() {
-    Map<Path, Root> rootMap = new HashMap<>();
-    Map<PackageIdentifier, Root> realPackageRoots = new HashMap<>();
+    Map<Path, ArtifactRoot> rootMap = new HashMap<>();
+    Map<PackageIdentifier, ArtifactRoot> realPackageRoots = new HashMap<>();
     for (Map.Entry<PackageIdentifier, Path> entry : packageRootsMap.entrySet()) {
-      Root root = rootMap.get(entry.getValue());
+      ArtifactRoot root = rootMap.get(entry.getValue());
       if (root == null) {
-        root = Root.asSourceRoot(entry.getValue());
+        root = ArtifactRoot.asSourceRoot(entry.getValue());
         rootMap.put(entry.getValue(), root);
       }
       realPackageRoots.put(entry.getKey(), root);

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PackageRootsNoSymlinkCreation.java b/src/main/java/com/google/devtools/build/lib/skyframe/PackageRootsNoSymlinkCreation.java
index d1ee84f..16f03e7 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/PackageRootsNoSymlinkCreation.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PackageRootsNoSymlinkCreation.java

@@ -16,8 +16,8 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.PackageRoots;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.vfs.Path;
 import java.util.Optional;
@@ -27,11 +27,11 @@
  * whose {@link PackageRootLookup} returns the unique source root for any given package identifier.
  */
 public class PackageRootsNoSymlinkCreation implements PackageRoots {
-  private final Root sourceRoot;
+  private final ArtifactRoot sourceRoot;
 
   @VisibleForTesting
   public PackageRootsNoSymlinkCreation(Path sourcePath) {
-    this.sourceRoot = Root.asSourceRoot(sourcePath);
+    this.sourceRoot = ArtifactRoot.asSourceRoot(sourcePath);
   }
 
   @Override

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
index 429caf8..2038e11 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java

@@ -48,11 +48,11 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.EnvironmentalExecException;
 import com.google.devtools.build.lib.actions.Executor;
 import com.google.devtools.build.lib.actions.FileStateType;
 import com.google.devtools.build.lib.actions.ResourceManager;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.AspectCollection;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ConfiguredAspect;
@@ -830,19 +830,19 @@
     return ImmutableList.of(value.getStableArtifact(), value.getVolatileArtifact());
   }
 
-  public Map<PathFragment, Root> getArtifactRootsForFiles(
+  public Map<PathFragment, ArtifactRoot> getArtifactRootsForFiles(
       final ExtendedEventHandler eventHandler, Iterable<PathFragment> execPaths)
       throws InterruptedException {
     return getArtifactRoots(eventHandler, execPaths, true);
   }
 
-  public Map<PathFragment, Root> getArtifactRoots(
+  public Map<PathFragment, ArtifactRoot> getArtifactRoots(
       final ExtendedEventHandler eventHandler, Iterable<PathFragment> execPaths)
       throws InterruptedException {
     return getArtifactRoots(eventHandler, execPaths, false);
   }
 
-  private Map<PathFragment, Root> getArtifactRoots(
+  private Map<PathFragment, ArtifactRoot> getArtifactRoots(
       final ExtendedEventHandler eventHandler, Iterable<PathFragment> execPaths, boolean forFiles)
       throws InterruptedException {
     final Map<PathFragment, SkyKey> packageKeys = new HashMap<>();
@@ -867,12 +867,13 @@
       return new HashMap<>();
     }
 
-    Map<PathFragment, Root> roots = new HashMap<>();
+    Map<PathFragment, ArtifactRoot> roots = new HashMap<>();
     for (PathFragment execPath : execPaths) {
       ContainingPackageLookupValue value = result.get(packageKeys.get(execPath));
       if (value.hasContainingPackage()) {
-        roots.put(execPath,
-            Root.computeSourceRoot(
+        roots.put(
+            execPath,
+            ArtifactRoot.computeSourceRoot(
                 value.getContainingPackageRoot(),
                 value.getContainingPackageName().getRepository()));
       } else {

diff --git a/src/test/java/com/google/devtools/build/lib/actions/ActionCacheCheckerTest.java b/src/test/java/com/google/devtools/build/lib/actions/ActionCacheCheckerTest.java
index c6de334..8892fcf 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/ActionCacheCheckerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ActionCacheCheckerTest.java

@@ -274,15 +274,16 @@
 
   @Test
   public void testMiddleman_DifferentFiles() throws Exception {
-    Action action = new NullMiddlemanAction() {
-      @Override
-      public synchronized Iterable<Artifact> getInputs() {
-        FileSystem fileSystem = getPrimaryOutput().getPath().getFileSystem();
-        Path path = fileSystem.getPath("/input");
-        Root root = Root.asSourceRoot(fileSystem.getPath("/"));
-        return ImmutableList.of(new Artifact(path, root));
-      }
-    };
+    Action action =
+        new NullMiddlemanAction() {
+          @Override
+          public synchronized Iterable<Artifact> getInputs() {
+            FileSystem fileSystem = getPrimaryOutput().getPath().getFileSystem();
+            Path path = fileSystem.getPath("/input");
+            ArtifactRoot root = ArtifactRoot.asSourceRoot(fileSystem.getPath("/"));
+            return ImmutableList.of(new Artifact(path, root));
+          }
+        };
     runAction(action);  // Not cached so recorded as different deps.
     FileSystemUtils.writeContentAsLatin1(action.getPrimaryInput().getPath(), "modified");
     runAction(action);  // Cache miss because input files were modified.

diff --git a/src/test/java/com/google/devtools/build/lib/actions/ActionLookupValueTest.java b/src/test/java/com/google/devtools/build/lib/actions/ActionLookupValueTest.java
index 5ae6c37..e2ddd4f 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/ActionLookupValueTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ActionLookupValueTest.java

@@ -58,7 +58,7 @@
   public void testActionNotPresentAfterEvaluation() {
     Path execRoot = fs.getPath("/execroot");
     Path outputRootPath = execRoot.getRelative("blaze-out");
-    Root root = Root.asDerivedRoot(execRoot, outputRootPath);
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(execRoot, outputRootPath);
     Action normalAction = mock(Action.class);
     Artifact normalArtifact = new Artifact(PathFragment.create("normal"), root);
     when(normalAction.getOutputs()).thenReturn(ImmutableSet.of(normalArtifact));

diff --git a/src/test/java/com/google/devtools/build/lib/actions/ArtifactFactoryTest.java b/src/test/java/com/google/devtools/build/lib/actions/ArtifactFactoryTest.java
index 5c6005d..94b1a0f 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/ArtifactFactoryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ArtifactFactoryTest.java

@@ -50,10 +50,10 @@
   private Scratch scratch = new Scratch();
 
   private Path execRoot;
-  private Root clientRoot;
-  private Root clientRoRoot;
-  private Root alienRoot;
-  private Root outRoot;
+  private ArtifactRoot clientRoot;
+  private ArtifactRoot clientRoRoot;
+  private ArtifactRoot alienRoot;
+  private ArtifactRoot outRoot;
 
   private PathFragment fooPath;
   private PackageIdentifier fooPackage;
@@ -73,10 +73,10 @@
   @Before
   public final void createFiles() throws Exception  {
     execRoot = scratch.dir("/output/workspace");
-    clientRoot = Root.asSourceRoot(scratch.dir("/client/workspace"));
-    clientRoRoot = Root.asSourceRoot(scratch.dir("/client/RO/workspace"));
-    alienRoot = Root.asSourceRoot(scratch.dir("/client/workspace"));
-    outRoot = Root.asDerivedRoot(execRoot, execRoot.getRelative("out-root/x/bin"));
+    clientRoot = ArtifactRoot.asSourceRoot(scratch.dir("/client/workspace"));
+    clientRoRoot = ArtifactRoot.asSourceRoot(scratch.dir("/client/RO/workspace"));
+    alienRoot = ArtifactRoot.asSourceRoot(scratch.dir("/client/workspace"));
+    outRoot = ArtifactRoot.asDerivedRoot(execRoot, execRoot.getRelative("out-root/x/bin"));
 
     fooPath = PathFragment.create("foo");
     fooPackage = PackageIdentifier.createInMainRepo(fooPath);
@@ -95,7 +95,7 @@
   }
 
   private void setupRoots() {
-    Map<PackageIdentifier, Root> packageRootMap = new HashMap<>();
+    Map<PackageIdentifier, ArtifactRoot> packageRootMap = new HashMap<>();
     packageRootMap.put(fooPackage, clientRoot);
     packageRootMap.put(barPackage, clientRoRoot);
     packageRootMap.put(alienPackage, alienRoot);
@@ -155,8 +155,8 @@
   public void testResolveArtifactWithUpLevelFailsCleanly() throws Exception {
     // We need a package in the root directory to make every exec path (even one with up-level
     // references) be in a package.
-    Map<PackageIdentifier, Root> packageRoots = ImmutableMap.of(
-        PackageIdentifier.createInMainRepo(PathFragment.create("")), clientRoot);
+    Map<PackageIdentifier, ArtifactRoot> packageRoots =
+        ImmutableMap.of(PackageIdentifier.createInMainRepo(PathFragment.create("")), clientRoot);
     artifactFactory.setPackageRoots(packageRoots::get);
     PathFragment outsideWorkspace = PathFragment.create("../foo");
     PathFragment insideWorkspace =
@@ -211,17 +211,18 @@
   }
 
   private static class MockPackageRootResolver implements PackageRootResolver {
-    private Map<PathFragment, Root> packageRoots = Maps.newHashMap();
+    private Map<PathFragment, ArtifactRoot> packageRoots = Maps.newHashMap();
 
-    public void setPackageRoots(Map<PackageIdentifier, Root> packageRoots) {
-      for (Entry<PackageIdentifier, Root> packageRoot : packageRoots.entrySet()) {
+    public void setPackageRoots(Map<PackageIdentifier, ArtifactRoot> packageRoots) {
+      for (Entry<PackageIdentifier, ArtifactRoot> packageRoot : packageRoots.entrySet()) {
         this.packageRoots.put(packageRoot.getKey().getPackageFragment(), packageRoot.getValue());
       }
     }
 
     @Override
-    public Map<PathFragment, Root> findPackageRootsForFiles(Iterable<PathFragment> execPaths) {
-      Map<PathFragment, Root> result = new HashMap<>();
+    public Map<PathFragment, ArtifactRoot> findPackageRootsForFiles(
+        Iterable<PathFragment> execPaths) {
+      Map<PathFragment, ArtifactRoot> result = new HashMap<>();
       for (PathFragment execPath : execPaths) {
         for (PathFragment dir = execPath.getParentDirectory(); dir != null;
             dir = dir.getParentDirectory()) {
@@ -238,7 +239,7 @@
 
     @Override
     @Nullable
-    public Map<PathFragment, Root> findPackageRoots(Iterable<PathFragment> execPaths) {
+    public Map<PathFragment, ArtifactRoot> findPackageRoots(Iterable<PathFragment> execPaths) {
       return null; // unused
     }
   }

diff --git a/src/test/java/com/google/devtools/build/lib/actions/RootTest.java b/src/test/java/com/google/devtools/build/lib/actions/ArtifactRootTest.java
similarity index 79%
rename from src/test/java/com/google/devtools/build/lib/actions/RootTest.java
rename to src/test/java/com/google/devtools/build/lib/actions/ArtifactRootTest.java
index 36ede38..dfe4e07 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/RootTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ArtifactRootTest.java

@@ -25,15 +25,15 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-/** Tests for {@link Root}. */
+/** Tests for {@link ArtifactRoot}. */
 @RunWith(JUnit4.class)
-public class RootTest {
+public class ArtifactRootTest {
   private Scratch scratch = new Scratch();
 
   @Test
   public void testAsSourceRoot() throws IOException {
     Path sourceDir = scratch.dir("/source");
-    Root root = Root.asSourceRoot(sourceDir);
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(sourceDir);
     assertThat(root.isSourceRoot()).isTrue();
     assertThat(root.getExecPath()).isEqualTo(PathFragment.EMPTY_FRAGMENT);
     assertThat(root.getPath()).isEqualTo(sourceDir);
@@ -43,7 +43,7 @@
   @Test
   public void testBadAsSourceRoot() {
     try {
-      Root.asSourceRoot(null);
+      ArtifactRoot.asSourceRoot(null);
       fail();
     } catch (NullPointerException expected) {
     }
@@ -53,7 +53,7 @@
   public void testAsDerivedRoot() throws IOException {
     Path execRoot = scratch.dir("/exec");
     Path rootDir = scratch.dir("/exec/root");
-    Root root = Root.asDerivedRoot(execRoot, rootDir);
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(execRoot, rootDir);
     assertThat(root.isSourceRoot()).isFalse();
     assertThat(root.getExecPath()).isEqualTo(PathFragment.create("root"));
     assertThat(root.getPath()).isEqualTo(rootDir);
@@ -65,7 +65,7 @@
     try {
       Path execRoot = scratch.dir("/exec");
       Path outsideDir = scratch.dir("/not_exec");
-      Root.asDerivedRoot(execRoot, outsideDir);
+      ArtifactRoot.asDerivedRoot(execRoot, outsideDir);
       fail();
     } catch (IllegalArgumentException expected) {
     }
@@ -75,7 +75,7 @@
   public void testBadAsDerivedRootSameForBoth() throws IOException {
     try {
       Path execRoot = scratch.dir("/exec");
-      Root.asDerivedRoot(execRoot, execRoot);
+      ArtifactRoot.asDerivedRoot(execRoot, execRoot);
       fail();
     } catch (IllegalArgumentException expected) {
     }
@@ -85,7 +85,7 @@
   public void testBadAsDerivedRootNullDir() throws IOException {
     try {
       Path execRoot = scratch.dir("/exec");
-      Root.asDerivedRoot(execRoot, null);
+      ArtifactRoot.asDerivedRoot(execRoot, null);
       fail();
     } catch (NullPointerException expected) {
     }
@@ -95,7 +95,7 @@
   public void testBadAsDerivedRootNullExecRoot() throws IOException {
     try {
       Path execRoot = scratch.dir("/exec");
-      Root.asDerivedRoot(null, execRoot);
+      ArtifactRoot.asDerivedRoot(null, execRoot);
       fail();
     } catch (NullPointerException expected) {
     }
@@ -107,11 +107,11 @@
     Path rootDir = scratch.dir("/exec/root");
     Path otherRootDir = scratch.dir("/");
     Path sourceDir = scratch.dir("/source");
-    Root rootA = Root.asDerivedRoot(execRoot, rootDir);
-    assertEqualsAndHashCode(true, rootA, Root.asDerivedRoot(execRoot, rootDir));
-    assertEqualsAndHashCode(false, rootA, Root.asSourceRoot(sourceDir));
-    assertEqualsAndHashCode(false, rootA, Root.asSourceRoot(rootDir));
-    assertEqualsAndHashCode(false, rootA, Root.asDerivedRoot(otherRootDir, rootDir));
+    ArtifactRoot rootA = ArtifactRoot.asDerivedRoot(execRoot, rootDir);
+    assertEqualsAndHashCode(true, rootA, ArtifactRoot.asDerivedRoot(execRoot, rootDir));
+    assertEqualsAndHashCode(false, rootA, ArtifactRoot.asSourceRoot(sourceDir));
+    assertEqualsAndHashCode(false, rootA, ArtifactRoot.asSourceRoot(rootDir));
+    assertEqualsAndHashCode(false, rootA, ArtifactRoot.asDerivedRoot(otherRootDir, rootDir));
   }
 
   public void assertEqualsAndHashCode(boolean expected, Object a, Object b) {

diff --git a/src/test/java/com/google/devtools/build/lib/actions/ArtifactTest.java b/src/test/java/com/google/devtools/build/lib/actions/ArtifactTest.java
index dda385f..681b2a3 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/ArtifactTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ArtifactTest.java

@@ -40,14 +40,14 @@
 public class ArtifactTest {
   private Scratch scratch;
   private Path execDir;
-  private Root rootDir;
+  private ArtifactRoot rootDir;
   private final ActionKeyContext actionKeyContext = new ActionKeyContext();
 
   @Before
   public final void setRootDir() throws Exception  {
     scratch = new Scratch();
     execDir = scratch.dir("/exec");
-    rootDir = Root.asDerivedRoot(execDir, scratch.dir("/exec/root"));
+    rootDir = ArtifactRoot.asDerivedRoot(execDir, scratch.dir("/exec/root"));
   }
 
   @Test
@@ -55,7 +55,7 @@
     Path f1 = scratch.file("/exec/dir/file.ext");
     Path bogusDir = scratch.file("/exec/dir/bogus");
     try {
-      new Artifact(f1, Root.asDerivedRoot(execDir, bogusDir), f1.relativeTo(execDir));
+      new Artifact(f1, ArtifactRoot.asDerivedRoot(execDir, bogusDir), f1.relativeTo(execDir));
       fail("Expected IllegalArgumentException constructing artifact with a bad root dir");
     } catch (IllegalArgumentException expected) {}
   }
@@ -97,7 +97,7 @@
   @Test
   public void testRootPrefixedExecPath_noRoot() throws IOException {
     Path f1 = scratch.file("/exec/dir/file.ext");
-    Artifact a1 = new Artifact(f1.relativeTo(execDir), Root.asSourceRoot(execDir));
+    Artifact a1 = new Artifact(f1.relativeTo(execDir), ArtifactRoot.asSourceRoot(execDir));
     assertThat(Artifact.asRootPrefixedExecPath(a1)).isEqualTo(":dir/file.ext");
   }
 
@@ -128,7 +128,7 @@
 
   @Test
   public void testGetFilename() throws Exception {
-    Root root = Root.asSourceRoot(scratch.dir("/foo"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.dir("/foo"));
     Artifact javaFile = new Artifact(scratch.file("/foo/Bar.java"), root);
     Artifact generatedHeader = new Artifact(scratch.file("/foo/bar.proto.h"), root);
     Artifact generatedCc = new Artifact(scratch.file("/foo/bar.proto.cc"), root);
@@ -141,7 +141,7 @@
 
   @Test
   public void testGetExtension() throws Exception {
-    Root root = Root.asSourceRoot(scratch.dir("/foo"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.dir("/foo"));
     Artifact javaFile = new Artifact(scratch.file("/foo/Bar.java"), root);
     assertThat(javaFile.getExtension()).isEqualTo("java");
   }
@@ -154,12 +154,14 @@
 
   private List<Artifact> getFooBarArtifacts(MutableActionGraph actionGraph, boolean collapsedList)
       throws Exception {
-    Root root = Root.asSourceRoot(scratch.dir("/foo"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.dir("/foo"));
     Artifact aHeader1 = new Artifact(scratch.file("/foo/bar1.h"), root);
     Artifact aHeader2 = new Artifact(scratch.file("/foo/bar2.h"), root);
     Artifact aHeader3 = new Artifact(scratch.file("/foo/bar3.h"), root);
-    Artifact middleman = new Artifact(PathFragment.create("middleman"),
-        Root.middlemanRoot(scratch.dir("/foo"), scratch.dir("/foo/out")));
+    Artifact middleman =
+        new Artifact(
+            PathFragment.create("middleman"),
+            ArtifactRoot.middlemanRoot(scratch.dir("/foo"), scratch.dir("/foo/out")));
     actionGraph.registerAction(new MiddlemanAction(ActionsTestUtil.NULL_ACTION_OWNER,
         ImmutableList.of(aHeader1, aHeader2, aHeader3), middleman, "desc",
         MiddlemanType.AGGREGATING_MIDDLEMAN));
@@ -270,7 +272,7 @@
 
   @Test
   public void testRootRelativePathIsSameAsExecPath() throws Exception {
-    Root root = Root.asSourceRoot(scratch.dir("/foo"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.dir("/foo"));
     Artifact a = new Artifact(scratch.file("/foo/bar1.h"), root);
     assertThat(a.getRootRelativePath()).isSameAs(a.getExecPath());
   }
@@ -281,7 +283,7 @@
     Artifact a =
         new Artifact(
             scratch.file("/a/b/c"),
-            Root.asDerivedRoot(execRoot, scratch.dir("/a/b")),
+            ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/a/b")),
             PathFragment.create("b/c"));
     assertThat(a.toDetailString()).isEqualTo("[[/a]b]c");
   }
@@ -292,7 +294,7 @@
       Path execRoot = scratch.getFileSystem().getPath("/");
       new Artifact(
           scratch.file("/a/b/c"),
-          Root.asDerivedRoot(execRoot, scratch.dir("/a")),
+          ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/a")),
           PathFragment.create("c"));
       fail();
     } catch (IllegalArgumentException e) {
@@ -305,7 +307,8 @@
   public void testSerializeToString() throws Exception {
     Path execRoot = scratch.getFileSystem().getPath("/");
     assertThat(
-            new Artifact(scratch.file("/a/b/c"), Root.asDerivedRoot(execRoot, scratch.dir("/a")))
+            new Artifact(
+                    scratch.file("/a/b/c"), ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/a")))
                 .serializeToString())
         .isEqualTo("a/b/c /3");
   }
@@ -314,7 +317,7 @@
   public void testSerializeToStringWithExecPath() throws Exception {
     Path execRoot = scratch.getFileSystem().getPath("/");
     Path path = scratch.file("/aaa/bbb/ccc");
-    Root root = Root.asDerivedRoot(execRoot, scratch.dir("/aaa/bbb"));
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/aaa/bbb"));
     PathFragment execPath = PathFragment.create("bbb/ccc");
 
     assertThat(new Artifact(path, root, execPath).serializeToString()).isEqualTo("bbb/ccc /3");
@@ -326,7 +329,7 @@
     assertThat(
             new Artifact(
                     scratch.file("/aa/b/c"),
-                    Root.asDerivedRoot(execRoot, scratch.dir("/aa")),
+                    ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/aa")),
                     PathFragment.create("b/c"),
                     new LabelArtifactOwner(Label.parseAbsoluteUnchecked("//foo:bar")))
                 .serializeToString())
@@ -343,7 +346,7 @@
   @Test
   public void testDirnameInExecutionDir() throws Exception {
     Artifact artifact =
-        new Artifact(scratch.file("/foo/bar.txt"), Root.asSourceRoot(scratch.dir("/foo")));
+        new Artifact(scratch.file("/foo/bar.txt"), ArtifactRoot.asSourceRoot(scratch.dir("/foo")));
 
     assertThat(artifact.getDirname()).isEqualTo(".");
   }
@@ -360,26 +363,30 @@
   @Test
   public void testIsSourceArtifact() throws Exception {
     assertThat(
-        new Artifact(scratch.file("/src/foo.cc"), Root.asSourceRoot(scratch.dir("/")),
-            PathFragment.create("src/foo.cc"))
-            .isSourceArtifact())
+            new Artifact(
+                    scratch.file("/src/foo.cc"),
+                    ArtifactRoot.asSourceRoot(scratch.dir("/")),
+                    PathFragment.create("src/foo.cc"))
+                .isSourceArtifact())
         .isTrue();
     assertThat(
-        new Artifact(scratch.file("/genfiles/aaa/bar.out"),
-            Root.asDerivedRoot(scratch.dir("/genfiles"), scratch.dir("/genfiles/aaa")))
-            .isSourceArtifact())
+            new Artifact(
+                    scratch.file("/genfiles/aaa/bar.out"),
+                    ArtifactRoot.asDerivedRoot(
+                        scratch.dir("/genfiles"), scratch.dir("/genfiles/aaa")))
+                .isSourceArtifact())
         .isFalse();
-
   }
 
   @Test
   public void testGetRoot() throws Exception {
     Path execRoot = scratch.getFileSystem().getPath("/");
-    Root root = Root.asDerivedRoot(execRoot, scratch.dir("/newRoot"));
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/newRoot"));
     assertThat(new Artifact(scratch.file("/newRoot/foo"), root).getRoot()).isEqualTo(root);
   }
 
   private Artifact createDirNameArtifact() throws Exception {
-    return new Artifact(scratch.file("/aaa/bbb/ccc/ddd"), Root.asSourceRoot(scratch.dir("/")));
+    return new Artifact(
+        scratch.file("/aaa/bbb/ccc/ddd"), ArtifactRoot.asSourceRoot(scratch.dir("/")));
   }
 }

diff --git a/src/test/java/com/google/devtools/build/lib/actions/CompositeRunfilesSupplierTest.java b/src/test/java/com/google/devtools/build/lib/actions/CompositeRunfilesSupplierTest.java
index e799800..dc6f752 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/CompositeRunfilesSupplierTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/CompositeRunfilesSupplierTest.java

@@ -40,13 +40,13 @@
   private RunfilesSupplier mockSecond;
 
   private Path execRoot;
-  private Root rootDir;
+  private ArtifactRoot rootDir;
 
   @Before
   public final void createMocks() throws IOException {
     Scratch scratch = new Scratch();
     execRoot = scratch.getFileSystem().getPath("/");
-    rootDir = Root.asDerivedRoot(execRoot, scratch.dir("/fake/root/dont/matter"));
+    rootDir = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/fake/root/dont/matter"));
 
     mockFirst = mock(RunfilesSupplier.class);
     mockSecond = mock(RunfilesSupplier.class);
@@ -131,7 +131,7 @@
         shared, firstSharedMappings);
    }
 
-  private static Map<PathFragment, Artifact> mkMappings(Root rootDir, String... paths) {
+  private static Map<PathFragment, Artifact> mkMappings(ArtifactRoot rootDir, String... paths) {
     ImmutableMap.Builder<PathFragment, Artifact> builder = ImmutableMap.builder();
     for (String path : paths) {
       builder.put(PathFragment.create(path), mkArtifact(rootDir, path));
@@ -139,11 +139,11 @@
     return builder.build();
   }
 
-  private static Artifact mkArtifact(Root rootDir, String path) {
+  private static Artifact mkArtifact(ArtifactRoot rootDir, String path) {
     return new Artifact(PathFragment.create(path), rootDir);
   }
 
-  private static List<Artifact> mkArtifacts(Root rootDir, String... paths) {
+  private static List<Artifact> mkArtifacts(ArtifactRoot rootDir, String... paths) {
     ImmutableList.Builder<Artifact> builder = ImmutableList.builder();
     for (String path : paths) {
       builder.add(mkArtifact(rootDir, path));

diff --git a/src/test/java/com/google/devtools/build/lib/actions/CustomCommandLineTest.java b/src/test/java/com/google/devtools/build/lib/actions/CustomCommandLineTest.java
index a907739..5227dba 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/CustomCommandLineTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/CustomCommandLineTest.java

@@ -44,14 +44,14 @@
 public class CustomCommandLineTest {
 
   private Scratch scratch;
-  private Root rootDir;
+  private ArtifactRoot rootDir;
   private Artifact artifact1;
   private Artifact artifact2;
 
   @Before
   public void createArtifacts() throws Exception  {
     scratch = new Scratch();
-    rootDir = Root.asSourceRoot(scratch.dir("/exec/root"));
+    rootDir = ArtifactRoot.asSourceRoot(scratch.dir("/exec/root"));
     artifact1 = new Artifact(scratch.file("/exec/root/dir/file1.txt"), rootDir);
     artifact2 = new Artifact(scratch.file("/exec/root/dir/file2.txt"), rootDir);
   }

diff --git a/src/test/java/com/google/devtools/build/lib/actions/ExecutableSymlinkActionTest.java b/src/test/java/com/google/devtools/build/lib/actions/ExecutableSymlinkActionTest.java
index 391ccf5..28da727 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/ExecutableSymlinkActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ExecutableSymlinkActionTest.java

@@ -35,8 +35,8 @@
 @RunWith(JUnit4.class)
 public class ExecutableSymlinkActionTest {
   private Scratch scratch = new Scratch();
-  private Root inputRoot;
-  private Root outputRoot;
+  private ArtifactRoot inputRoot;
+  private ArtifactRoot outputRoot;
   TestFileOutErr outErr;
   private Executor executor;
   private final ActionKeyContext actionKeyContext = new ActionKeyContext();
@@ -45,8 +45,8 @@
   public final void createExecutor() throws Exception  {
     final Path inputDir = scratch.dir("/in");
     Path execRoot = scratch.getFileSystem().getPath("/");
-    inputRoot = Root.asDerivedRoot(execRoot, inputDir);
-    outputRoot = Root.asDerivedRoot(execRoot, scratch.dir("/out"));
+    inputRoot = ArtifactRoot.asDerivedRoot(execRoot, inputDir);
+    outputRoot = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/out"));
     outErr = new TestFileOutErr();
     executor = new DummyExecutor(scratch.getFileSystem(), inputDir);
   }

diff --git a/src/test/java/com/google/devtools/build/lib/actions/FailActionTest.java b/src/test/java/com/google/devtools/build/lib/actions/FailActionTest.java
index 5b39c35..c1eac8e 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/FailActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/FailActionTest.java

@@ -42,8 +42,10 @@
   @Before
   public final void setUp() throws Exception  {
     errorMessage = "An error just happened.";
-    anOutput = new Artifact(scratch.file("/out/foo"),
-        Root.asDerivedRoot(scratch.dir("/"), scratch.dir("/out")));
+    anOutput =
+        new Artifact(
+            scratch.file("/out/foo"),
+            ArtifactRoot.asDerivedRoot(scratch.dir("/"), scratch.dir("/out")));
     outputs = ImmutableList.of(anOutput);
     failAction = new FailAction(NULL_ACTION_OWNER, outputs, errorMessage);
     actionGraph.registerAction(failAction);

diff --git a/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java b/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java
index 7d4a752..5de14d9 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/MapBasedActionGraphTest.java

@@ -45,13 +45,13 @@
     Path execRoot = fileSystem.getPath("/");
     Path root = fileSystem.getPath("/root");
     Path path = root.getRelative("foo");
-    Artifact output = new Artifact(path, Root.asDerivedRoot(execRoot, root));
+    Artifact output = new Artifact(path, ArtifactRoot.asDerivedRoot(execRoot, root));
     Action action = new TestAction(TestAction.NO_EFFECT,
         ImmutableSet.<Artifact>of(), ImmutableSet.of(output));
     actionGraph.registerAction(action);
     actionGraph.unregisterAction(action);
     path = root.getRelative("bar");
-    output = new Artifact(path, Root.asDerivedRoot(execRoot, root));
+    output = new Artifact(path, ArtifactRoot.asDerivedRoot(execRoot, root));
     Action action2 = new TestAction(TestAction.NO_EFFECT,
         ImmutableSet.<Artifact>of(), ImmutableSet.of(output));
     actionGraph.registerAction(action);
@@ -65,7 +65,7 @@
     Path execRoot = fileSystem.getPath("/");
     Path root = fileSystem.getPath("/root");
     Path path = root.getRelative("/root/foo");
-    Artifact output = new Artifact(path, Root.asDerivedRoot(execRoot, root));
+    Artifact output = new Artifact(path, ArtifactRoot.asDerivedRoot(execRoot, root));
     Action action = new TestAction(TestAction.NO_EFFECT,
         ImmutableSet.<Artifact>of(), ImmutableSet.of(output));
     actionGraph.registerAction(action);
@@ -94,7 +94,7 @@
       Path execRoot = fileSystem.getPath("/");
       Path root = fileSystem.getPath("/root");
       Path path = root.getRelative("foo");
-      output = new Artifact(path, Root.asDerivedRoot(execRoot, root));
+      output = new Artifact(path, ArtifactRoot.asDerivedRoot(execRoot, root));
       allActions.add(new TestAction(
           TestAction.NO_EFFECT, ImmutableSet.<Artifact>of(), ImmutableSet.of(output)));
     }

diff --git a/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java b/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java
index ecd3fc3..c3f8e0f 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/util/ActionsTestUtil.java

@@ -42,11 +42,11 @@
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
 import com.google.devtools.build.lib.actions.ArtifactResolver;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.Executor;
 import com.google.devtools.build.lib.actions.MutableActionGraph;
 import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
 import com.google.devtools.build.lib.actions.PackageRootResolver;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.cache.Md5Digest;
 import com.google.devtools.build.lib.actions.cache.Metadata;
 import com.google.devtools.build.lib.actions.cache.MetadataHandler;
@@ -243,9 +243,10 @@
     }
   }
 
-  public static final Artifact DUMMY_ARTIFACT = new Artifact(
-      PathFragment.create("dummy"),
-      Root.asSourceRoot(new InMemoryFileSystem().getRootDirectory()));
+  public static final Artifact DUMMY_ARTIFACT =
+      new Artifact(
+          PathFragment.create("dummy"),
+          ArtifactRoot.asSourceRoot(new InMemoryFileSystem().getRootDirectory()));
 
   public static final ActionOwner NULL_ACTION_OWNER =
       ActionOwner.create(
@@ -673,12 +674,12 @@
   public static class FakeArtifactResolverBase implements ArtifactResolver {
     @Override
     public Artifact getSourceArtifact(
-        PathFragment execPath, Root root, ArtifactOwner owner) {
+        PathFragment execPath, ArtifactRoot root, ArtifactOwner owner) {
       throw new UnsupportedOperationException();
     }
 
     @Override
-    public Artifact getSourceArtifact(PathFragment execPath, Root root) {
+    public Artifact getSourceArtifact(PathFragment execPath, ArtifactRoot root) {
       throw new UnsupportedOperationException();
     }
 

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java
index 676255f..f1de38e 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/LocationFunctionTest.java

@@ -19,7 +19,7 @@
 
 import com.google.common.base.Suppliers;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.LocationExpander.LocationFunction;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.vfs.FileSystem;
@@ -47,9 +47,10 @@
   private Artifact makeArtifact(String path) {
     if (path.startsWith("/exec/out")) {
       return new Artifact(
-          fs.getPath(path), Root.asDerivedRoot(fs.getPath("/exec"), fs.getPath("/exec/out")));
+          fs.getPath(path),
+          ArtifactRoot.asDerivedRoot(fs.getPath("/exec"), fs.getPath("/exec/out")));
     } else {
-      return new Artifact(fs.getPath(path), Root.asSourceRoot(fs.getPath("/exec")));
+      return new Artifact(fs.getPath(path), ArtifactRoot.asSourceRoot(fs.getPath("/exec")));
     }
   }
 

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/RunfilesSupplierImplTest.java b/src/test/java/com/google/devtools/build/lib/analysis/RunfilesSupplierImplTest.java
index 3967b0e..952d013 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/RunfilesSupplierImplTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/RunfilesSupplierImplTest.java

@@ -19,7 +19,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.testutil.Scratch;
 import com.google.devtools.build.lib.vfs.Path;
@@ -36,17 +36,18 @@
 public class RunfilesSupplierImplTest {
 
   private Path execRoot;
-  private Root rootDir;
-  private Root middlemanRoot;
+  private ArtifactRoot rootDir;
+  private ArtifactRoot middlemanRoot;
 
   @Before
   public final void setRoot() throws IOException {
     Scratch scratch = new Scratch();
     execRoot = scratch.getFileSystem().getPath("/");
-    rootDir = Root.asDerivedRoot(execRoot, scratch.dir("/fake/root/dont/matter"));
+    rootDir = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/fake/root/dont/matter"));
 
     Path middlemanExecPath = scratch.dir("/still/fake/root/dont/matter");
-    middlemanRoot = Root.middlemanRoot(middlemanExecPath, middlemanExecPath.getChild("subdir"));
+    middlemanRoot =
+        ArtifactRoot.middlemanRoot(middlemanExecPath, middlemanExecPath.getChild("subdir"));
   }
 
   @Test
@@ -90,7 +91,7 @@
     return new Runfiles.Builder("TESTING", false).addArtifacts(artifacts).build();
   }
 
-  private static List<Artifact> mkArtifacts(Root rootDir, String... paths) {
+  private static List<Artifact> mkArtifacts(ArtifactRoot rootDir, String... paths) {
     ImmutableList.Builder<Artifact> builder = ImmutableList.builder();
     for (String path : paths) {
       builder.add(new Artifact(PathFragment.create(path), rootDir));

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/RunfilesTest.java b/src/test/java/com/google/devtools/build/lib/analysis/RunfilesTest.java
index 5a16caa..ec184e8 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/RunfilesTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/RunfilesTest.java

@@ -21,7 +21,7 @@
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.events.EventKind;
 import com.google.devtools.build.lib.testutil.FoundationTestCase;
@@ -51,7 +51,7 @@
   public void testFilterListForObscuringSymlinksCatchesBadObscurer() throws Exception {
     Map<PathFragment, Artifact> obscuringMap = new HashMap<>();
     PathFragment pathA = PathFragment.create("a");
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     Artifact artifactA = new Artifact(PathFragment.create("a"), root);
     obscuringMap.put(pathA, artifactA);
     obscuringMap.put(PathFragment.create("a/b"), new Artifact(PathFragment.create("c/b"),
@@ -65,7 +65,7 @@
   public void testFilterListForObscuringSymlinksCatchesBadGrandParentObscurer() throws Exception {
     Map<PathFragment, Artifact> obscuringMap = new HashMap<>();
     PathFragment pathA = PathFragment.create("a");
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     Artifact artifactA = new Artifact(PathFragment.create("a"),
                                           root);
     obscuringMap.put(pathA, artifactA);
@@ -80,7 +80,7 @@
   public void testFilterListForObscuringSymlinksCatchesBadObscurerNoListener() throws Exception {
     Map<PathFragment, Artifact> obscuringMap = new HashMap<>();
     PathFragment pathA = PathFragment.create("a");
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     Artifact artifactA = new Artifact(PathFragment.create("a"),
                                           root);
     obscuringMap.put(pathA, artifactA);
@@ -94,7 +94,7 @@
   public void testFilterListForObscuringSymlinksIgnoresOkObscurer() throws Exception {
     Map<PathFragment, Artifact> obscuringMap = new HashMap<>();
     PathFragment pathA = PathFragment.create("a");
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     Artifact artifactA = new Artifact(PathFragment.create("a"),
                                           root);
     obscuringMap.put(pathA, artifactA);
@@ -110,7 +110,7 @@
   public void testFilterListForObscuringSymlinksNoObscurers() throws Exception {
     Map<PathFragment, Artifact> obscuringMap = new HashMap<>();
     PathFragment pathA = PathFragment.create("a");
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     Artifact artifactA = new Artifact(PathFragment.create("a"),
                                           root);
     obscuringMap.put(pathA, artifactA);
@@ -142,7 +142,7 @@
 
   @Test
   public void testPutCatchesConflict() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Artifact artifactC = new Artifact(PathFragment.create("c"), root);
@@ -159,7 +159,7 @@
 
   @Test
   public void testPutReportsError() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Artifact artifactC = new Artifact(PathFragment.create("c"), root);
@@ -177,7 +177,7 @@
 
   @Test
   public void testPutCatchesConflictBetweenNullAndNotNull() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Map<PathFragment, Artifact> map = new LinkedHashMap<>();
@@ -192,7 +192,7 @@
 
   @Test
   public void testPutCatchesConflictBetweenNotNullAndNull() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Map<PathFragment, Artifact> map = new LinkedHashMap<>();
@@ -208,7 +208,7 @@
 
   @Test
   public void testPutIgnoresConflict() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Artifact artifactC = new Artifact(PathFragment.create("c"), root);
@@ -224,7 +224,7 @@
 
   @Test
   public void testPutIgnoresConflictNoListener() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Artifact artifactC = new Artifact(PathFragment.create("c"), root);
@@ -240,7 +240,7 @@
 
   @Test
   public void testPutIgnoresSameArtifact() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     Artifact artifactB = new Artifact(PathFragment.create("b"), root);
     Artifact artifactB2 = new Artifact(PathFragment.create("b"), root);
@@ -271,7 +271,7 @@
 
   @Test
   public void testPutNoConflicts() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathA = PathFragment.create("a");
     PathFragment pathB = PathFragment.create("b");
     PathFragment pathC = PathFragment.create("c");
@@ -325,7 +325,7 @@
 
   @Test
   public void testLegacyRunfilesStructure() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment workspaceName = PathFragment.create("wsname");
     PathFragment pathB = PathFragment.create("external/repo/b");
     Artifact artifactB = new Artifact(pathB, root);
@@ -346,7 +346,7 @@
 
   @Test
   public void testRunfileAdded() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment workspaceName = PathFragment.create("wsname");
     PathFragment pathB = PathFragment.create("external/repo/b");
     Artifact artifactB = new Artifact(pathB, root);
@@ -369,7 +369,7 @@
   // TODO(kchodorow): remove this once the default workspace name is always set.
   @Test
   public void testConflictWithExternal() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     PathFragment pathB = PathFragment.create("repo/b");
     PathFragment externalPathB = Label.EXTERNAL_PACKAGE_NAME.getRelative(pathB);
     Artifact artifactB = new Artifact(pathB, root);
@@ -393,7 +393,7 @@
 
   @Test
   public void testMergeWithSymlinks() {
-    Root root = Root.asSourceRoot(scratch.resolve("/workspace"));
+    ArtifactRoot root = ArtifactRoot.asSourceRoot(scratch.resolve("/workspace"));
     Artifact artifactA = new Artifact(PathFragment.create("a/target"), root);
     Artifact artifactB = new Artifact(PathFragment.create("b/target"), root);
     PathFragment sympathA = PathFragment.create("a/symlink");
@@ -412,7 +412,8 @@
 
   @Test
   public void testOnlyExtraMiddlemenNotConsideredEmpty() {
-    Root root = Root.middlemanRoot(scratch.resolve("execroot"), scratch.resolve("execroot/out"));
+    ArtifactRoot root =
+        ArtifactRoot.middlemanRoot(scratch.resolve("execroot"), scratch.resolve("execroot/out"));
     Artifact mm = new Artifact(PathFragment.create("a-middleman"), root);
     Runfiles runfiles = new Runfiles.Builder("TESTING").addLegacyExtraMiddleman(mm).build();
     assertThat(runfiles.isEmpty()).isFalse();
@@ -420,7 +421,8 @@
 
   @Test
   public void testMergingExtraMiddlemen() {
-    Root root = Root.middlemanRoot(scratch.resolve("execroot"), scratch.resolve("execroot/out"));
+    ArtifactRoot root =
+        ArtifactRoot.middlemanRoot(scratch.resolve("execroot"), scratch.resolve("execroot/out"));
     Artifact mm1 = new Artifact(PathFragment.create("middleman-1"), root);
     Artifact mm2 = new Artifact(PathFragment.create("middleman-2"), root);
     Runfiles runfiles1 = new Runfiles.Builder("TESTING").addLegacyExtraMiddleman(mm1).build();

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/TopLevelArtifactHelperTest.java b/src/test/java/com/google/devtools/build/lib/analysis/TopLevelArtifactHelperTest.java
index 9609bed..141982d 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/TopLevelArtifactHelperTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/TopLevelArtifactHelperTest.java

@@ -23,7 +23,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.TopLevelArtifactHelper.ArtifactsInOutputGroup;
 import com.google.devtools.build.lib.analysis.TopLevelArtifactHelper.ArtifactsToBuild;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
@@ -45,14 +45,14 @@
   private OutputGroupInfo groupProvider;
 
   private Path path;
-  private Root root;
+  private ArtifactRoot root;
   private int artifactIdx;
 
   @Before
   public final void setRootDir() throws Exception {
     Scratch scratch = new Scratch();
     Path execRoot = scratch.getFileSystem().getPath("/");
-    root = Root.asDerivedRoot(execRoot, scratch.dir("/blaze-out"));
+    root = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/blaze-out"));
     path = scratch.dir("/blaze-out/foo");
   }
 

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/actions/ParamFileWriteActionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/actions/ParamFileWriteActionTest.java
index 1a541ff..ed382c4 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/actions/ParamFileWriteActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/actions/ParamFileWriteActionTest.java

@@ -28,9 +28,9 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.Executor;
 import com.google.devtools.build.lib.actions.ParameterFile.ParameterFileType;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.util.ActionTester;
 import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
@@ -50,14 +50,14 @@
 /** Tests for ParamFileWriteAction. */
 @RunWith(JUnit4.class)
 public class ParamFileWriteActionTest extends BuildViewTestCase {
-  private Root rootDir;
+  private ArtifactRoot rootDir;
   private Artifact outputArtifact;
   private Artifact treeArtifact;
 
   @Before
   public void createArtifacts() throws Exception  {
     Path execRoot = scratch.getFileSystem().getPath("/exec");
-    rootDir = Root.asDerivedRoot(execRoot, scratch.dir("/exec/out"));
+    rootDir = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/exec/out"));
     outputArtifact = getBinArtifactWithNoOwner("destination.txt");
     FileSystemUtils.createDirectoryAndParents(outputArtifact.getPath().getParentDirectory());
     treeArtifact = createTreeArtifact("artifact/myTreeFileArtifact");

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/actions/PopulateTreeArtifactActionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/actions/PopulateTreeArtifactActionTest.java
index 96f5afe..5a54a9e0 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/actions/PopulateTreeArtifactActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/actions/PopulateTreeArtifactActionTest.java

@@ -31,9 +31,9 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.BaseSpawn;
 import com.google.devtools.build.lib.actions.Executor;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.Spawn;
 import com.google.devtools.build.lib.actions.SpawnActionContext;
 import com.google.devtools.build.lib.actions.cache.Md5Digest;
@@ -106,12 +106,12 @@
     }
   };
 
-  private Root root;
+  private ArtifactRoot root;
 
   @Before
   public void setRootDir() throws Exception  {
     Path execRoot = scratch.getFileSystem().getPath("/exec");
-    root = Root.asDerivedRoot(execRoot, scratch.dir("/exec/out"));
+    root = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/exec/out"));
   }
 
   @Test

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/actions/SpawnActionTemplateTest.java b/src/test/java/com/google/devtools/build/lib/analysis/actions/SpawnActionTemplateTest.java
index b325e3b..a13091d 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/actions/SpawnActionTemplateTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/actions/SpawnActionTemplateTest.java

@@ -24,7 +24,7 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.actions.SpawnActionTemplate.OutputPathMapper;
 import com.google.devtools.build.lib.testutil.Scratch;
@@ -48,13 +48,13 @@
     }
   };
 
-  private Root root;
+  private ArtifactRoot root;
 
   @Before
   public void setRootDir() throws Exception  {
     Scratch scratch = new Scratch();
     Path execRoot = scratch.getFileSystem().getPath("/");
-    root = Root.asDerivedRoot(execRoot, scratch.dir("/exec/root"));
+    root = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/exec/root"));
   }
 
   @Test

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/actions/TemplateExpansionActionTest.java b/src/test/java/com/google/devtools/build/lib/analysis/actions/TemplateExpansionActionTest.java
index 2528e3b..3f6e62d 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/actions/TemplateExpansionActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/actions/TemplateExpansionActionTest.java

@@ -24,8 +24,8 @@
 import com.google.devtools.build.lib.actions.ActionInputPrefetcher;
 import com.google.devtools.build.lib.actions.ActionKeyContext;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.Executor;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ServerDirectories;
 import com.google.devtools.build.lib.analysis.actions.TemplateExpansionAction.Substitution;
@@ -52,7 +52,7 @@
   private static final String TEMPLATE = Joiner.on('\n').join("key=%key%", "value=%value%");
   private static final String SPECIAL_CHARS = "Š©±½_strøget";
 
-  private Root outputRoot;
+  private ArtifactRoot outputRoot;
   private Artifact inputArtifact;
   private Artifact outputArtifact;
   private Path output;
@@ -77,8 +77,9 @@
   }
 
   private void createArtifacts(String template) throws Exception {
-    Root workspace = Root.asSourceRoot(scratch.dir("/workspace"));
-    outputRoot = Root.asDerivedRoot(scratch.dir("/workspace"), scratch.dir("/workspace/out"));
+    ArtifactRoot workspace = ArtifactRoot.asSourceRoot(scratch.dir("/workspace"));
+    outputRoot =
+        ArtifactRoot.asDerivedRoot(scratch.dir("/workspace"), scratch.dir("/workspace/out"));
     Path input = scratch.overwriteFile("/workspace/input.txt", StandardCharsets.UTF_8, template);
     inputArtifact = new Artifact(input, workspace);
     output = scratch.resolve("/workspace/out/destination.txt");

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/util/AnalysisTestUtil.java b/src/test/java/com/google/devtools/build/lib/analysis/util/AnalysisTestUtil.java
index 8e3f755..1a5c6ea 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/util/AnalysisTestUtil.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/util/AnalysisTestUtil.java

@@ -29,11 +29,11 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.ExecutionStrategy;
 import com.google.devtools.build.lib.actions.MiddlemanFactory;
 import com.google.devtools.build.lib.actions.MutableActionGraph;
 import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.AnalysisEnvironment;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
@@ -120,22 +120,22 @@
     }
 
     @Override
-    public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return original.getDerivedArtifact(rootRelativePath, root);
     }
 
     @Override
-    public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return original.getConstantMetadataArtifact(rootRelativePath, root);
     }
 
     @Override
-    public Artifact getTreeArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getTreeArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return null;
     }
 
     @Override
-    public Artifact getFilesetArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getFilesetArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return original.getFilesetArtifact(rootRelativePath, root);
     }
 
@@ -326,12 +326,12 @@
     }
 
     @Override
-    public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return null;
     }
 
     @Override
-    public Artifact getTreeArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getTreeArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return null;
     }
 
@@ -366,12 +366,12 @@
     }
 
     @Override
-    public Artifact getFilesetArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getFilesetArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return null;
     }
 
     @Override
-    public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       return null;
     }
 
@@ -462,7 +462,7 @@
 
     Set<String> files = new LinkedHashSet<>();
     for (Artifact artifact : artifacts) {
-      Root root = artifact.getRoot();
+      ArtifactRoot root = artifact.getRoot();
       if (root.isSourceRoot()) {
         files.add("src " + artifact.getRootRelativePath());
       } else {

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/util/BuildViewTestCase.java b/src/test/java/com/google/devtools/build/lib/analysis/util/BuildViewTestCase.java
index 457d184..a448942 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/util/BuildViewTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/util/BuildViewTestCase.java

@@ -36,13 +36,13 @@
 import com.google.devtools.build.lib.actions.ActionKeyContext;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.CommandLineExpansionException;
 import com.google.devtools.build.lib.actions.MapBasedActionGraph;
 import com.google.devtools.build.lib.actions.MiddlemanFactory;
 import com.google.devtools.build.lib.actions.MutableActionGraph;
 import com.google.devtools.build.lib.actions.ResourceManager;
 import com.google.devtools.build.lib.actions.ResourceSet;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.AnalysisEnvironment;
 import com.google.devtools.build.lib.analysis.AnalysisUtils;
@@ -970,12 +970,12 @@
         .isSameAs(getGeneratingActionForLabel(labelA));
   }
 
-  protected Artifact getSourceArtifact(PathFragment rootRelativePath, Root root) {
+  protected Artifact getSourceArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
     return view.getArtifactFactory().getSourceArtifact(rootRelativePath, root);
   }
 
   protected Artifact getSourceArtifact(String name) {
-    return getSourceArtifact(PathFragment.create(name), Root.asSourceRoot(rootDirectory));
+    return getSourceArtifact(PathFragment.create(name), ArtifactRoot.asSourceRoot(rootDirectory));
   }
 
   /**
@@ -985,7 +985,7 @@
    * #getBinArtifactWithNoOwner} or {@link #getGenfilesArtifactWithNoOwner} should be used instead.
    */
   protected Artifact getDerivedArtifact(
-      PathFragment rootRelativePath, Root root, ArtifactOwner owner) {
+      PathFragment rootRelativePath, ArtifactRoot root, ArtifactOwner owner) {
     return view.getArtifactFactory().getDerivedArtifact(rootRelativePath, root, owner);
   }
 
@@ -993,10 +993,10 @@
    * Gets a derived Artifact for testing with path of the form
    * root/owner.getPackageFragment()/packageRelativePath.
    *
-   * @see #getDerivedArtifact(PathFragment, Root, ArtifactOwner)
+   * @see #getDerivedArtifact(PathFragment, ArtifactRoot, ArtifactOwner)
    */
-  private Artifact getPackageRelativeDerivedArtifact(String packageRelativePath, Root root,
-      ArtifactOwner owner) {
+  private Artifact getPackageRelativeDerivedArtifact(
+      String packageRelativePath, ArtifactRoot root, ArtifactOwner owner) {
     return getDerivedArtifact(
         owner.getLabel().getPackageFragment().getRelative(packageRelativePath),
         root, owner);
@@ -1708,12 +1708,12 @@
     }
 
     @Override
-    public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getConstantMetadataArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       throw new UnsupportedOperationException();
     }
 
     @Override
-    public Artifact getTreeArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getTreeArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       throw new UnsupportedOperationException();
     }
 
@@ -1748,12 +1748,12 @@
     }
 
     @Override
-    public Artifact getFilesetArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getFilesetArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       throw new UnsupportedOperationException();
     }
 
     @Override
-    public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root) {
+    public Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
       throw new UnsupportedOperationException();
     }
 
@@ -1925,7 +1925,7 @@
     Rule associatedRule = target.getTarget().getAssociatedRule();
     RepositoryName repository = associatedRule.getRepository();
 
-    Root root;
+    ArtifactRoot root;
     if (associatedRule.hasBinaryOutput()) {
       root = configuration.getBinDirectory(repository);
     } else {

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/util/ConfigurationTestCase.java b/src/test/java/com/google/devtools/build/lib/analysis/util/ConfigurationTestCase.java
index c142337..7953c33 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/util/ConfigurationTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/util/ConfigurationTestCase.java

@@ -20,7 +20,7 @@
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.actions.ActionKeyContext;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
 import com.google.devtools.build.lib.analysis.ServerDirectories;
@@ -201,7 +201,7 @@
 
   public void assertConfigurationsHaveUniqueOutputDirectories(
       BuildConfigurationCollection configCollection) throws Exception {
-    Map<Root, BuildConfiguration> outputPaths = new HashMap<>();
+    Map<ArtifactRoot, BuildConfiguration> outputPaths = new HashMap<>();
     for (BuildConfiguration config : configCollection.getTargetConfigurations()) {
       if (config.isActionsEnabled()) {
         BuildConfiguration otherConfig = outputPaths.get(

diff --git a/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java b/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java
index 4099d2e..a71ba03 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/FilesetManifestTest.java

@@ -20,7 +20,7 @@
 import static org.junit.Assert.fail;
 
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
@@ -58,7 +58,7 @@
     // See AnalysisUtils for the mapping from "foo" to "_foo/MANIFEST".
     scratchFile("/root/_foo/MANIFEST");
 
-    Artifact artifact = new Artifact(fs.getPath("/root/foo"), Root.asSourceRoot(execRoot));
+    Artifact artifact = new Artifact(fs.getPath("/root/foo"), ArtifactRoot.asSourceRoot(execRoot));
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
     assertThat(manifest.getEntries()).isEmpty();
@@ -72,7 +72,8 @@
         "workspace/bar /dir/file",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
@@ -90,7 +91,8 @@
         "workspace/baz /dir/file",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
@@ -108,7 +110,8 @@
         "workspace/bar /some",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
@@ -125,7 +128,8 @@
         "workspace/bar ", // <-- Note the trailing whitespace!
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
@@ -140,7 +144,8 @@
         "notworkspace/bar /foo/bar",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     try {
       FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
@@ -162,7 +167,8 @@
         "workspace/foo /foo/bar",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     try {
       FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", ERROR);
@@ -182,7 +188,8 @@
         "workspace/foo /foo/bar",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);
@@ -200,7 +207,8 @@
         "workspace/foo /foo/bar",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", RESOLVE);
@@ -218,7 +226,8 @@
         "workspace/bar foo",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     try {
       FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", RESOLVE);
@@ -242,7 +251,8 @@
         "workspace/bar /baz",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     FilesetManifest manifest =
         FilesetManifest.parseManifestFile(artifact, execRoot, "workspace", IGNORE);

diff --git a/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java b/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
index 71359fd..9e14fac 100644
--- a/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java

@@ -20,8 +20,8 @@
 import com.google.devtools.build.lib.actions.ActionInput;
 import com.google.devtools.build.lib.actions.ActionInputHelper;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.EmptyRunfilesSupplier;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.analysis.Runfiles;
 import com.google.devtools.build.lib.analysis.RunfilesSupplierImpl;
@@ -76,7 +76,7 @@
   @Test
   public void testRunfilesSingleFile() throws Exception {
     Artifact artifact =
-        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/file"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Runfiles runfiles = new Runfiles.Builder("workspace").addArtifact(artifact).build();
     RunfilesSupplier supplier = new RunfilesSupplierImpl(PathFragment.create("runfiles"), runfiles);
     FakeActionInputFileCache mockCache = new FakeActionInputFileCache();
@@ -91,7 +91,7 @@
   @Test
   public void testRunfilesDirectoryStrict() throws Exception {
     Artifact artifact =
-        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/file"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Runfiles runfiles = new Runfiles.Builder("workspace").addArtifact(artifact).build();
     RunfilesSupplier supplier = new RunfilesSupplierImpl(PathFragment.create("runfiles"), runfiles);
     FakeActionInputFileCache mockCache = new FakeActionInputFileCache();
@@ -108,7 +108,7 @@
   @Test
   public void testRunfilesDirectoryNonStrict() throws Exception {
     Artifact artifact =
-        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/file"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Runfiles runfiles = new Runfiles.Builder("workspace").addArtifact(artifact).build();
     RunfilesSupplier supplier = new RunfilesSupplierImpl(PathFragment.create("runfiles"), runfiles);
     FakeActionInputFileCache mockCache = new FakeActionInputFileCache();
@@ -124,9 +124,9 @@
   @Test
   public void testRunfilesTwoFiles() throws Exception {
     Artifact artifact1 =
-        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/file"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Artifact artifact2 =
-        new Artifact(fs.getPath("/root/dir/baz"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/baz"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Runfiles runfiles = new Runfiles.Builder("workspace")
         .addArtifact(artifact1)
         .addArtifact(artifact2)
@@ -147,7 +147,7 @@
   @Test
   public void testRunfilesSymlink() throws Exception {
     Artifact artifact =
-        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/file"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Runfiles runfiles = new Runfiles.Builder("workspace")
         .addSymlink(PathFragment.create("symlink"), artifact).build();
     RunfilesSupplier supplier = new RunfilesSupplierImpl(PathFragment.create("runfiles"), runfiles);
@@ -163,7 +163,7 @@
   @Test
   public void testRunfilesRootSymlink() throws Exception {
     Artifact artifact =
-        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+        new Artifact(fs.getPath("/root/dir/file"), ArtifactRoot.asSourceRoot(fs.getPath("/root")));
     Runfiles runfiles = new Runfiles.Builder("workspace")
         .addRootSymlink(PathFragment.create("symlink"), artifact).build();
     RunfilesSupplier supplier = new RunfilesSupplierImpl(PathFragment.create("runfiles"), runfiles);
@@ -185,7 +185,8 @@
     // See AnalysisUtils for the mapping from "foo" to "_foo/MANIFEST".
     scratchFile("/root/out/_foo/MANIFEST");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     expander.parseFilesetManifest(inputMappings, artifact, "workspace");
     assertThat(inputMappings).isEmpty();
@@ -199,7 +200,8 @@
         "workspace/bar /dir/file",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     expander.parseFilesetManifest(inputMappings, artifact, "workspace");
     assertThat(inputMappings).hasSize(1);
@@ -217,7 +219,8 @@
         "workspace/baz /dir/file",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     expander.parseFilesetManifest(inputMappings, artifact, "workspace");
     assertThat(inputMappings).hasSize(2);
@@ -235,7 +238,8 @@
         "workspace/bar /some",
         "<some digest>");
 
-    Root outputRoot = Root.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
+    ArtifactRoot outputRoot =
+        ArtifactRoot.asDerivedRoot(fs.getPath("/root"), fs.getPath("/root/out"));
     Artifact artifact = new Artifact(fs.getPath("/root/out/foo"), outputRoot);
     expander.parseFilesetManifest(inputMappings, artifact, "workspace");
     assertThat(inputMappings).hasSize(1);

diff --git a/src/test/java/com/google/devtools/build/lib/remote/TreeNodeRepositoryTest.java b/src/test/java/com/google/devtools/build/lib/remote/TreeNodeRepositoryTest.java
index 8c4f35e..48953ce 100644
--- a/src/test/java/com/google/devtools/build/lib/remote/TreeNodeRepositoryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/remote/TreeNodeRepositoryTest.java

@@ -20,7 +20,7 @@
 import com.google.devtools.build.lib.actions.ActionInputFileCache;
 import com.google.devtools.build.lib.actions.ActionInputHelper;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.clock.BlazeClock;
 import com.google.devtools.build.lib.exec.SingleBuildFileCache;
 import com.google.devtools.build.lib.remote.TreeNodeRepository.TreeNode;
@@ -46,14 +46,14 @@
   private Scratch scratch;
   private DigestUtil digestUtil;
   private Path execRoot;
-  private Root rootDir;
+  private ArtifactRoot rootDir;
 
   @Before
   public final void setRootDir() throws Exception {
     digestUtil = new DigestUtil(HashFunction.SHA256);
     scratch = new Scratch(new InMemoryFileSystem(BlazeClock.instance(), HashFunction.SHA256));
     execRoot = scratch.getFileSystem().getPath("/exec/root");
-    rootDir = Root.asSourceRoot(scratch.dir("/exec/root"));
+    rootDir = ArtifactRoot.asSourceRoot(scratch.dir("/exec/root"));
   }
 
   private TreeNodeRepository createTestTreeNodeRepository() {

diff --git a/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java b/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java
index f86a574..37bcf0d 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/android/ResourceTestBase.java

@@ -21,7 +21,7 @@
 import com.google.common.collect.Multimap;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
 import com.google.devtools.build.lib.packages.AbstractRuleErrorConsumer;
@@ -156,13 +156,13 @@
 
   public FakeRuleErrorConsumer errorConsumer;
   public FileSystem fileSystem;
-  public Root root;
+  public ArtifactRoot root;
 
   @Before
   public void setup() {
     errorConsumer = new FakeRuleErrorConsumer();
     fileSystem = new InMemoryFileSystem();
-    root = Root.asSourceRoot(fileSystem.getRootDirectory());
+    root = ArtifactRoot.asSourceRoot(fileSystem.getRootDirectory());
   }
 
   @After

diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CompileCommandLineTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CompileCommandLineTest.java
index 99aa8a7..1e9b36d 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CompileCommandLineTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CompileCommandLineTest.java

@@ -18,7 +18,7 @@
 import com.google.common.base.Predicate;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.FeatureConfiguration;
 import com.google.devtools.build.lib.rules.cpp.CompileCommandLine.Builder;
@@ -42,7 +42,7 @@
   private Artifact scratchArtifact(String s) {
     Path execRoot = outputBase.getRelative("exec");
     Path outputRoot = execRoot.getRelative("root");
-    Root root = Root.asDerivedRoot(execRoot, outputRoot);
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(execRoot, outputRoot);
     try {
       return new Artifact(scratch.overwriteFile(outputRoot.getRelative(s).toString()), root);
     } catch (IOException e) {

diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionTest.java
index 6107747..703c3ff 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionTest.java

@@ -30,8 +30,8 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.ResourceSet;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
 import com.google.devtools.build.lib.analysis.RuleContext;
@@ -82,7 +82,7 @@
           }
 
           @Override
-          public Artifact getDerivedArtifact(PathFragment rootRelativePath, Root root) {
+          public Artifact getDerivedArtifact(PathFragment rootRelativePath, ArtifactRoot root) {
             return CppLinkActionTest.this.getDerivedArtifact(
                 rootRelativePath, root, ActionsTestUtil.NULL_ARTIFACT_OWNER);
           }
@@ -533,7 +533,7 @@
   private Artifact scratchArtifact(String s) {
     Path execRoot = outputBase.getRelative("exec");
     Path outputRoot = execRoot.getRelative("out");
-    Root root = Root.asDerivedRoot(execRoot, outputRoot);
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(execRoot, outputRoot);
     try {
       return new Artifact(scratch.overwriteFile(outputRoot.getRelative(s).toString()), root);
     } catch (IOException e) {
@@ -673,7 +673,7 @@
     Path path = execRoot.getRelative(execPath);
     return new SpecialArtifact(
         path,
-        Root.asDerivedRoot(execRoot, execRoot.getRelative("out")),
+        ArtifactRoot.asDerivedRoot(execRoot, execRoot.getRelative("out")),
         execPath,
         ArtifactOwner.NULL_OWNER,
         SpecialArtifactType.TREE);

diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CreateIncSymlinkActionTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CreateIncSymlinkActionTest.java
index b7ea510..273d986 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CreateIncSymlinkActionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CreateIncSymlinkActionTest.java

@@ -20,7 +20,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.actions.ActionKeyContext;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.testutil.FoundationTestCase;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -39,7 +39,7 @@
 
   @Test
   public void testDifferentOrderSameActionKey() throws Exception {
-    Root root = Root.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out"));
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out"));
     Artifact a = new Artifact(PathFragment.create("a"), root);
     Artifact b = new Artifact(PathFragment.create("b"), root);
     Artifact c = new Artifact(PathFragment.create("c"), root);
@@ -59,7 +59,7 @@
 
   @Test
   public void testDifferentTargetsDifferentActionKey() throws Exception {
-    Root root = Root.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out"));
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out"));
     Artifact a = new Artifact(PathFragment.create("a"), root);
     Artifact b = new Artifact(PathFragment.create("b"), root);
     CreateIncSymlinkAction action1 = new CreateIncSymlinkAction(NULL_ACTION_OWNER,
@@ -75,7 +75,7 @@
 
   @Test
   public void testDifferentSymlinksDifferentActionKey() throws Exception {
-    Root root = Root.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out"));
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out"));
     Artifact a = new Artifact(PathFragment.create("a"), root);
     Artifact b = new Artifact(PathFragment.create("b"), root);
     CreateIncSymlinkAction action1 = new CreateIncSymlinkAction(NULL_ACTION_OWNER,
@@ -93,7 +93,7 @@
   public void testExecute() throws Exception {
     Path outputDir = rootDirectory.getRelative("out");
     outputDir.createDirectory();
-    Root root = Root.asDerivedRoot(rootDirectory, outputDir);
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(rootDirectory, outputDir);
     Path symlink = rootDirectory.getRelative("out/a");
     Artifact a = new Artifact(symlink, root);
     Artifact b = new Artifact(PathFragment.create("b"), root);
@@ -110,7 +110,7 @@
   public void testFileRemoved() throws Exception {
     Path outputDir = rootDirectory.getRelative("out");
     outputDir.createDirectory();
-    Root root = Root.asDerivedRoot(rootDirectory, outputDir);
+    ArtifactRoot root = ArtifactRoot.asDerivedRoot(rootDirectory, outputDir);
     Path symlink = rootDirectory.getRelative("out/subdir/a");
     Artifact a = new Artifact(symlink, root);
     Artifact b = new Artifact(PathFragment.create("b"), root);

diff --git a/src/test/java/com/google/devtools/build/lib/rules/objc/J2ObjcSourceTest.java b/src/test/java/com/google/devtools/build/lib/rules/objc/J2ObjcSourceTest.java
index 043476e..0486cd3 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/objc/J2ObjcSourceTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/objc/J2ObjcSourceTest.java

@@ -17,7 +17,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.testing.EqualsTester;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.testutil.Scratch;
 import com.google.devtools.build.lib.vfs.Path;
@@ -32,13 +32,13 @@
  */
 @RunWith(JUnit4.class)
 public class J2ObjcSourceTest {
-  private Root rootDir;
+  private ArtifactRoot rootDir;
 
   @Before
   public final void setRootDir() throws Exception  {
     Scratch scratch = new Scratch();
     Path execRoot = scratch.getFileSystem().getPath("/exec");
-    rootDir = Root.asDerivedRoot(execRoot, scratch.dir("/exec/root"));
+    rootDir = ArtifactRoot.asDerivedRoot(execRoot, scratch.dir("/exec/root"));
   }
 
   @Test

diff --git a/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java b/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java
index 44cc3f8..08d6f9c 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/proto/ProtoCompileActionBuilderTest.java

@@ -23,7 +23,7 @@
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.util.LabelArtifactOwner;
 import com.google.devtools.build.lib.analysis.FilesToRunProvider;
 import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
@@ -45,9 +45,9 @@
 public class ProtoCompileActionBuilderTest {
 
   private static final InMemoryFileSystem FILE_SYSTEM = new InMemoryFileSystem();
-  private final Root root = Root.asSourceRoot(FILE_SYSTEM.getPath("/"));
-  private final Root derivedRoot =
-      Root.asDerivedRoot(FILE_SYSTEM.getPath("/"), FILE_SYSTEM.getPath("/out"));
+  private final ArtifactRoot root = ArtifactRoot.asSourceRoot(FILE_SYSTEM.getPath("/"));
+  private final ArtifactRoot derivedRoot =
+      ArtifactRoot.asDerivedRoot(FILE_SYSTEM.getPath("/"), FILE_SYSTEM.getPath("/out"));
 
   @Test
   public void commandLine_basic() throws Exception {

diff --git a/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java b/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java
index 81b4328..b522705 100644
--- a/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/runtime/BuildEventStreamerTest.java

@@ -26,8 +26,8 @@
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.EventReportingArtifacts;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ServerDirectories;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
@@ -520,7 +520,7 @@
 
   private Artifact makeArtifact(String pathString) {
     Path path = outputBase.getRelative(PathFragment.create(pathString));
-    return new Artifact(path, Root.asSourceRoot(outputBase));
+    return new Artifact(path, ArtifactRoot.asSourceRoot(outputBase));
   }
 
   @Test

diff --git a/src/test/java/com/google/devtools/build/lib/runtime/ExperimentalStateTrackerTest.java b/src/test/java/com/google/devtools/build/lib/runtime/ExperimentalStateTrackerTest.java
index b9133f3..b7db0b3 100644
--- a/src/test/java/com/google/devtools/build/lib/runtime/ExperimentalStateTrackerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/runtime/ExperimentalStateTrackerTest.java

@@ -31,7 +31,7 @@
 import com.google.devtools.build.lib.actions.ActionStartedEvent;
 import com.google.devtools.build.lib.actions.ActionStatusMessage;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
 import com.google.devtools.build.lib.bazel.repository.downloader.DownloadProgressEvent;
 import com.google.devtools.build.lib.buildeventstream.AnnounceBuildEventTransportsEvent;
@@ -68,7 +68,7 @@
 
   private Action mockAction(String progressMessage, String primaryOutput) {
     Path path = outputBase.getRelative(PathFragment.create(primaryOutput));
-    Artifact artifact = new Artifact(path, Root.asSourceRoot(outputBase));
+    Artifact artifact = new Artifact(path, ArtifactRoot.asSourceRoot(outputBase));
 
     Action action = Mockito.mock(Action.class);
     when(action.getProgressMessage()).thenReturn(progressMessage);
@@ -473,7 +473,7 @@
 
     ManualClock clock = new ManualClock();
     Path path = outputBase.getRelative(PathFragment.create(primaryOutput));
-    Artifact artifact = new Artifact(path, Root.asSourceRoot(outputBase));
+    Artifact artifact = new Artifact(path, ArtifactRoot.asSourceRoot(outputBase));
     ActionExecutionMetadata actionMetadata = Mockito.mock(ActionExecutionMetadata.class);
     when(actionMetadata.getOwner()).thenReturn(Mockito.mock(ActionOwner.class));
     when(actionMetadata.getPrimaryOutput()).thenReturn(artifact);

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ActionTemplateExpansionFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ActionTemplateExpansionFunctionTest.java
index 8e55e34..f122174 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ActionTemplateExpansionFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ActionTemplateExpansionFunctionTest.java

@@ -30,8 +30,8 @@
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
 import com.google.devtools.build.lib.actions.ArtifactPrefixConflictException;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
 import com.google.devtools.build.lib.analysis.actions.SpawnActionTemplate;
@@ -209,7 +209,7 @@
     Path fullPath = rootDirectory.getRelative(execPath);
     return new SpecialArtifact(
         fullPath,
-        Root.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out")),
+        ArtifactRoot.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out")),
         execPath,
         ArtifactOwner.NULL_OWNER,
         SpecialArtifactType.TREE);

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java
index aba2931..339ad4e 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java

@@ -31,8 +31,8 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifact;
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MissingInputFileException;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.actions.util.TestAction.DummyAction;
 import com.google.devtools.build.lib.events.NullEventHandler;
@@ -245,7 +245,7 @@
   }
 
   private Artifact createSourceArtifact(String path) {
-    return new Artifact(PathFragment.create(path), Root.asSourceRoot(root));
+    return new Artifact(PathFragment.create(path), ArtifactRoot.asSourceRoot(root));
   }
 
   private Artifact createDerivedArtifact(String path) {
@@ -253,13 +253,17 @@
     Path fullPath = root.getRelative(execPath);
     Artifact output =
         new Artifact(
-            fullPath, Root.asDerivedRoot(root, root.getRelative("out")), execPath, ALL_OWNER);
+            fullPath,
+            ArtifactRoot.asDerivedRoot(root, root.getRelative("out")),
+            execPath,
+            ALL_OWNER);
     actions.add(new DummyAction(ImmutableList.<Artifact>of(), output));
     return output;
   }
 
   private Artifact createMiddlemanArtifact(String path) {
-    Root middlemanRoot = Root.middlemanRoot(middlemanPath, middlemanPath.getRelative("out"));
+    ArtifactRoot middlemanRoot =
+        ArtifactRoot.middlemanRoot(middlemanPath, middlemanPath.getRelative("out"));
     Path fullPath = middlemanRoot.getPath().getRelative(path);
     return new Artifact(
         fullPath, middlemanRoot, fullPath.relativeTo(middlemanRoot.getExecRoot()), ALL_OWNER);
@@ -276,7 +280,7 @@
     Path fullPath = root.getRelative(execPath);
     return new SpecialArtifact(
         fullPath,
-        Root.asDerivedRoot(root, root.getRelative("out")),
+        ArtifactRoot.asDerivedRoot(root, root.getRelative("out")),
         execPath,
         ALL_OWNER,
         SpecialArtifactType.TREE);

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FilesetEntryFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FilesetEntryFunctionTest.java
index 90ed181..2671226 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FilesetEntryFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FilesetEntryFunctionTest.java

@@ -25,11 +25,11 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.FilesetOutputSymlink;
 import com.google.devtools.build.lib.actions.FilesetTraversalParams;
 import com.google.devtools.build.lib.actions.FilesetTraversalParams.PackageBoundaryMode;
 import com.google.devtools.build.lib.actions.FilesetTraversalParamsFactory;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ServerDirectories;
 import com.google.devtools.build.lib.cmdline.Label;
@@ -129,7 +129,7 @@
   }
 
   private Artifact getSourceArtifact(String path) throws Exception {
-    return new Artifact(PathFragment.create(path), Root.asSourceRoot(rootDirectory));
+    return new Artifact(PathFragment.create(path), ArtifactRoot.asSourceRoot(rootDirectory));
   }
 
   private Artifact createSourceArtifact(String path) throws Exception {

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
index 5005910..01ed4fd 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java

@@ -29,7 +29,7 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.ArtifactOwner;
-import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.util.TestAction;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ServerDirectories;
@@ -608,14 +608,14 @@
     Path outputPath = fs.getPath("/bin");
     outputPath.createDirectory();
     return new Artifact(
-        outputPath.getRelative(relPath), Root.asDerivedRoot(fs.getPath("/"), outputPath));
+        outputPath.getRelative(relPath), ArtifactRoot.asDerivedRoot(fs.getPath("/"), outputPath));
   }
 
   private Artifact createTreeArtifact(String relPath) throws IOException {
     Path outputDir = fs.getPath("/bin");
     Path outputPath = outputDir.getRelative(relPath);
     outputDir.createDirectory();
-    Root derivedRoot = Root.asDerivedRoot(fs.getPath("/"), outputDir);
+    ArtifactRoot derivedRoot = ArtifactRoot.asDerivedRoot(fs.getPath("/"), outputDir);
     return new SpecialArtifact(outputPath, derivedRoot,
         derivedRoot.getExecPath().getRelative(outputPath.relativeTo(derivedRoot.getPath())),
         ArtifactOwner.NULL_OWNER, SpecialArtifactType.TREE);

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/RecursiveFilesystemTraversalFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/RecursiveFilesystemTraversalFunctionTest.java
index bb54b99..1779162 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/RecursiveFilesystemTraversalFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/RecursiveFilesystemTraversalFunctionTest.java

@@ -28,8 +28,8 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.FilesetTraversalParams.PackageBoundaryMode;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
 import com.google.devtools.build.lib.analysis.ServerDirectories;
@@ -150,12 +150,13 @@
   }
 
   private Artifact sourceArtifact(String path) {
-    return new Artifact(PathFragment.create(path), Root.asSourceRoot(rootDirectory));
+    return new Artifact(PathFragment.create(path), ArtifactRoot.asSourceRoot(rootDirectory));
   }
 
   private Artifact sourceArtifactUnderPackagePath(String path, String packagePath) {
     return new Artifact(
-        PathFragment.create(path), Root.asSourceRoot(rootDirectory.getRelative(packagePath)));
+        PathFragment.create(path),
+        ArtifactRoot.asSourceRoot(rootDirectory.getRelative(packagePath)));
   }
 
   private Artifact derivedArtifact(String path) {
@@ -164,7 +165,7 @@
     Artifact output =
         new Artifact(
             fullPath,
-            Root.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out")),
+            ArtifactRoot.asDerivedRoot(rootDirectory, rootDirectory.getRelative("out")),
             execPath);
     return output;
   }

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java b/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java
index 8e569fc..e5a2ade 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/TimestampBuilderTestCase.java

@@ -40,11 +40,11 @@
 import com.google.devtools.build.lib.actions.ActionLookupValue;
 import com.google.devtools.build.lib.actions.ActionResult;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.BuildFailedException;
 import com.google.devtools.build.lib.actions.Executor;
 import com.google.devtools.build.lib.actions.ResourceManager;
 import com.google.devtools.build.lib.actions.ResourceSet;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.TestExecException;
 import com.google.devtools.build.lib.actions.cache.ActionCache;
 import com.google.devtools.build.lib.actions.cache.Protos.ActionCacheStatistics;
@@ -327,7 +327,7 @@
 
   Artifact createSourceArtifact(FileSystem fs, String name) {
     Path root = fs.getPath(TestUtils.tmpDir());
-    return new Artifact(PathFragment.create(name), Root.asSourceRoot(root));
+    return new Artifact(PathFragment.create(name), ArtifactRoot.asSourceRoot(root));
   }
 
   protected Artifact createDerivedArtifact(String name) {
@@ -340,7 +340,7 @@
     Path path = execRoot.getRelative(execPath);
     return new Artifact(
         path,
-        Root.asDerivedRoot(execRoot, execRoot.getRelative("out")),
+        ArtifactRoot.asDerivedRoot(execRoot, execRoot.getRelative("out")),
         execPath,
         ACTION_LOOKUP_KEY);
   }

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactBuildTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactBuildTest.java
index 3846003..1a9063b 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactBuildTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactBuildTest.java

@@ -40,8 +40,8 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifact;
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.BuildFailedException;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.cache.MetadataHandler;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.actions.util.TestAction;
@@ -1183,7 +1183,7 @@
     Path path = execRoot.getRelative(execPath);
     return new SpecialArtifact(
         path,
-        Root.asDerivedRoot(execRoot, execRoot.getRelative("out")),
+        ArtifactRoot.asDerivedRoot(execRoot, execRoot.getRelative("out")),
         execPath,
         ACTION_LOOKUP_KEY,
         SpecialArtifactType.TREE);

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactMetadataTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactMetadataTest.java
index 0f346d6..3c32a9d 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactMetadataTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/TreeArtifactMetadataTest.java

@@ -32,8 +32,8 @@
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifact;
 import com.google.devtools.build.lib.actions.Artifact.SpecialArtifactType;
 import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
+import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.MissingInputFileException;
-import com.google.devtools.build.lib.actions.Root;
 import com.google.devtools.build.lib.actions.cache.DigestUtils;
 import com.google.devtools.build.lib.actions.cache.Metadata;
 import com.google.devtools.build.lib.actions.util.TestAction.DummyAction;
@@ -207,7 +207,10 @@
     Path fullPath = root.getRelative(execPath);
     Artifact output =
         new SpecialArtifact(
-            fullPath, Root.asDerivedRoot(root, root.getRelative("out")), execPath, ALL_OWNER,
+            fullPath,
+            ArtifactRoot.asDerivedRoot(root, root.getRelative("out")),
+            execPath,
+            ALL_OWNER,
             SpecialArtifactType.TREE);
     actions.add(new DummyAction(ImmutableList.<Artifact>of(), output));
     FileSystemUtils.createDirectoryAndParents(fullPath);