diff --git a/build-support/caching.coffee b/build-support/caching.coffee
index f1889a127e..79bf7baf7f 100644
--- a/build-support/caching.coffee
+++ b/build-support/caching.coffee
@@ -48,11 +48,39 @@ exports.Checksummed = class Checksummed
 
 exports.ChecksumFiles = class ChecksumFiles
   constructor: (paths) ->
-    @inputs = paths.map (p) -> path.resolve p
+    @sources = paths.map (p) -> path.resolve p
       .sort()
       .map (p) -> new FileContent p
 
-  digestAll: -> await Promise.all @inputs.map (f) -> await Checksummed.digestContent f
+  digestAll: -> await Promise.all @sources.map (f) -> await Checksummed.digestContent f
+
+
+exports.TaskFailed = class TaskFailed extends Error
+  constructor: (task, cause) ->
+    message = "task failed: #{task.print()}\n#{cause.message}"
+    super message, {cause}
+    @task = task
+
+  title: -> @task.print()
+  operation: -> @cause.operation?()
+  reason: -> @cause.reason?()
+  inner: -> @cause.inner?()
+
+  print: (console, {useColors}) ->
+    console.error "task failed: #{@title()}"
+
+    operation = "operation: #{@operation()}"
+    if useColors
+      operation = util.styleText 'yellow', operation
+    console.info operation
+
+    reason = "reason: #{@reason()}"
+    if useColors
+      reason = util.styleText 'cyan', reason
+    console.info reason
+
+    if (inner = @inner())?
+      console.error util.styleText 'reset', inner
 
 
 class Attestation
@@ -125,34 +153,6 @@ class Attestation
     @constructor.objectEquals cached, generated
 
 
-exports.TaskFailed = class TaskFailed extends Error
-  constructor: (task, cause) ->
-    message = "task failed: #{task.print()}\n#{cause.message}"
-    super message, {cause}
-    @task = task
-
-  title: -> @task.print()
-  operation: -> @cause.operation?()
-  reason: -> @cause.reason?()
-  inner: -> @cause.inner?()
-
-  print: (console, {useColors}) ->
-    console.error "task failed: #{@title()}"
-
-    operation = "operation: #{@operation()}"
-    if useColors
-      operation = util.styleText 'yellow', operation
-    console.info operation
-
-    reason = "reason: #{@reason()}"
-    if useColors
-      reason = util.styleText 'cyan', reason
-    console.info reason
-
-    if (inner = @inner())?
-      console.error util.styleText 'reset', inner
-
-
 exports.BuildTask = class BuildTask
   identifier: -> throw new TypeError "unimplemented: #{@constructor.name}"
   inputSources: -> throw new TypeError "unimplemented: #{@constructor.name}"
diff --git a/build-support/graph.coffee b/build-support/graph.coffee
new file mode 100644
index 0000000000..9215715e97
--- /dev/null
+++ b/build-support/graph.coffee
@@ -0,0 +1,54 @@
+assert = require 'assert'
+
+
+class ProductRelations
+  constructor: ->
+    @in = new Set
+    @out = new Set
+
+  addInput: (taskId) ->
+    assert (not @in.has taskId), taskId
+    @in.add taskId
+
+  addOutput: (taskId) ->
+    assert (not @out.has taskId), taskId
+    @out.add taskId
+
+
+class ProductRegistry
+  constructor: ->
+    @graph = new Map
+    @knownTasks = new Map
+    @knownContent = new Map
+
+  ensureNewTask: (task) ->
+    taskId = task.identifier()
+    assert (not @knownTasks.has taskId), taskId
+    @knownTasks.set taskId, task
+    taskId
+
+  maybeNewContent: (content) ->
+    contentId = content.identifier()
+    @knownContent.set contentId, content
+    contentId
+
+  setupRelations: (contentId) ->
+    if @graph.has contentId
+      return @graph.get contentId
+    relations = new ProductRelations
+    @graph.set contentId, relations
+    relations
+
+  registerTask: (task) ->
+    taskId = @ensureNewTask task
+
+    for {sources} in task.inputSources()
+      for i in sources
+        contentId = @maybeNewContent i
+        relations = @setupRelations contentId
+        relations.addInput taskId
+    for {sources} in task.outputSources()
+      for o in sources
+        contentId = @maybeNewContent o
+        relations = @setupRelations contentId
+        relations.addOutput taskId