diff --git a/android/deapexer.go b/android/deapexer.go
index 63508d7..f3c541c 100644
--- a/android/deapexer.go
+++ b/android/deapexer.go
@@ -15,31 +15,67 @@
 package android
 
 import (
-	"fmt"
-	"strings"
-
 	"github.com/google/blueprint"
 )
 
 // Provides support for interacting with the `deapexer` module to which a `prebuilt_apex` module
 // will delegate the work to export files from a prebuilt '.apex` file.
+//
+// The actual processing that is done is quite convoluted but it is all about combining information
+// from multiple different sources in order to allow a prebuilt module to use a file extracted from
+// an apex file. As follows:
+//
+// 1. A prebuilt module, e.g. prebuilt_bootclasspath_fragment or java_import needs to use a file
+//    from a prebuilt_apex/apex_set. It knows the path of the file within the apex but does not know
+//    where the apex file is or what apex to use.
+//
+// 2. The connection between the prebuilt module and the prebuilt_apex/apex_set is created through
+//    use of an exported_... property on the latter. That causes four things to occur:
+//    a. A `deapexer` mopdule is created by the prebuilt_apex/apex_set to extract files from the
+//       apex file.
+//    b. A dependency is added from the prebuilt_apex/apex_set modules onto the prebuilt modules
+//       listed in those properties.
+//    c. An APEX variant is created for each of those prebuilt modules.
+//    d. A dependency is added from the prebuilt modules to the `deapexer` module.
+//
+// 3. The prebuilt_apex/apex_set modules do not know which files are available in the apex file.
+//    That information could be specified on the prebuilt_apex/apex_set modules but without
+//    automated generation of those modules it would be expensive to maintain. So, instead they
+//    obtain that information from the prebuilt modules. They do not know what files are actually in
+//    the apex file either but they know what files they need from it. So, the
+//    prebuilt_apex/apex_set modules obtain the files that should be in the apex file from those
+//    modules and then pass those onto the `deapexer` module.
+//
+// 4. The `deapexer` module's ninja rule extracts all the files from the apex file into an output
+//    directory and checks that all the expected files are there. The expected files are declared as
+//    the outputs of the ninja rule so they are available to other modules.
+//
+// 5. The prebuilt modules then retrieve the paths to the files that they needed from the `deapexer`
+//    module.
+//
+// The files that are passed to `deapexer` and those that are passed back have a unique identifier
+// that links them together. e.g. If the `deapexer` is passed something like this:
+//     core-libart{.dexjar} -> javalib/core-libart.jar
+// it will return something like this:
+//     core-libart{.dexjar} -> out/soong/.....deapexer.../javalib/core-libart.jar
+//
+// The reason why the `deapexer` module is separate from the prebuilt_apex/apex_set is to avoid
+// cycles. e.g.
+//   prebuilt_apex "com.android.art" depends upon java_import "core-libart":
+//       This is so it can create an APEX variant of the latter and obtain information about the
+//       files that it needs from the apex file.
+//   java_import "core-libart" depends upon `deapexer` module:
+//       This is so it can retrieve the paths to the files it needs.
 
 // The information exported by the `deapexer` module, access it using `DeapxerInfoProvider`.
 type DeapexerInfo struct {
 	// map from the name of an exported file from a prebuilt_apex to the path to that file. The
-	// exported file name is of the form <module>{<tag>} where <tag> is currently only allowed to be
-	// ".dexjar".
+	// exported file name is of the form <module>{<tag>}.
 	//
 	// See Prebuilt.ApexInfoMutator for more information.
 	exports map[string]Path
 }
 
-// The set of supported prebuilt export tags. Used to verify the tag parameter for
-// `PrebuiltExportPath`.
-var supportedPrebuiltExportTags = map[string]struct{}{
-	".dexjar": {},
-}
-
 // PrebuiltExportPath provides the path, or nil if not available, of a file exported from the
 // prebuilt_apex that created this ApexInfo.
 //
@@ -51,12 +87,6 @@
 //
 // See apex/deapexer.go for more information.
 func (i DeapexerInfo) PrebuiltExportPath(name, tag string) Path {
-
-	if _, ok := supportedPrebuiltExportTags[tag]; !ok {
-		panic(fmt.Errorf("unsupported prebuilt export tag %q, expected one of %s",
-			tag, strings.Join(SortedStringKeys(supportedPrebuiltExportTags), ", ")))
-	}
-
 	path := i.exports[name+"{"+tag+"}"]
 	return path
 }
@@ -79,5 +109,22 @@
 	blueprint.BaseDependencyTag
 }
 
+// Mark this tag so dependencies that use it are excluded from APEX contents.
+func (t deapexerTagStruct) ExcludeFromApexContents() {}
+
+var _ ExcludeFromApexContentsTag = DeapexerTag
+
 // A tag that is used for dependencies on the `deapexer` module.
 var DeapexerTag = deapexerTagStruct{}
+
+// RequiredFilesFromPrebuiltApex must be implemented by modules that require files to be exported
+// from a prebuilt_apex/apex_set.
+type RequiredFilesFromPrebuiltApex interface {
+	// RequiredFilesFromPrebuiltApex returns a map from the key (module name plus tag) to the required
+	// path of the file within the prebuilt .apex file.
+	//
+	// For each key/file pair this will cause the file to be extracted out of the prebuilt .apex file,
+	// and the path to the extracted file will be stored in the DeapexerInfo using that key, The path
+	// can then be retrieved using the PrebuiltExportPath(name, tag) method.
+	RequiredFilesFromPrebuiltApex(ctx BaseModuleContext) map[string]string
+}