diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index 3a0a788..7d266f6 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -955,8 +955,15 @@
   return metadata
 
 
-class StreamingPropertyFiles(object):
-  """Computes the ota-streaming-property-files string for streaming A/B OTA.
+class PropertyFiles(object):
+  """A class that computes the property-files string for an OTA package.
+
+  A property-files string is a comma-separated string that contains the
+  offset/size info for an OTA package. The entries, which must be ZIP_STORED,
+  can be fetched directly with the package URL along with the offset/size info.
+  These strings can be used for streaming A/B OTAs, or allowing an updater to
+  download package metadata entry directly, without paying the cost of
+  downloading entire package.
 
   Computing the final property-files string requires two passes. Because doing
   the whole package signing (with signapk.jar) will possibly reorder the ZIP
@@ -966,7 +973,7 @@
   This class provides functions to be called for each pass. The general flow is
   as follows.
 
-    property_files = StreamingPropertyFiles()
+    property_files = PropertyFiles()
     # The first pass, which writes placeholders before doing initial signing.
     property_files.Compute()
     SignOutput()
@@ -981,17 +988,9 @@
   """
 
   def __init__(self):
-    self.required = (
-        # payload.bin and payload_properties.txt must exist.
-        'payload.bin',
-        'payload_properties.txt',
-    )
-    self.optional = (
-        # care_map.txt is available only if dm-verity is enabled.
-        'care_map.txt',
-        # compatibility.zip is available only if target supports Treble.
-        'compatibility.zip',
-    )
+    self.name = None
+    self.required = ()
+    self.optional = ()
 
   def Compute(self, input_zip):
     """Computes and returns a property-files string with placeholders.
@@ -1083,7 +1082,26 @@
     return ','.join(tokens)
 
 
-def FinalizeMetadata(metadata, input_file, output_file):
+class StreamingPropertyFiles(PropertyFiles):
+  """A subclass for computing the property-files for streaming A/B OTAs."""
+
+  def __init__(self):
+    super(StreamingPropertyFiles, self).__init__()
+    self.name = 'ota-streaming-property-files'
+    self.required = (
+        # payload.bin and payload_properties.txt must exist.
+        'payload.bin',
+        'payload_properties.txt',
+    )
+    self.optional = (
+        # care_map.txt is available only if dm-verity is enabled.
+        'care_map.txt',
+        # compatibility.zip is available only if target supports Treble.
+        'compatibility.zip',
+    )
+
+
+def FinalizeMetadata(metadata, input_file, output_file, needed_property_files):
   """Finalizes the metadata and signs an A/B OTA package.
 
   In order to stream an A/B OTA package, we need 'ota-streaming-property-files'
@@ -1101,14 +1119,14 @@
     input_file: The input ZIP filename that doesn't contain the package METADATA
         entry yet.
     output_file: The final output ZIP filename.
+    needed_property_files: The list of PropertyFiles' to be generated.
   """
   output_zip = zipfile.ZipFile(
       input_file, 'a', compression=zipfile.ZIP_DEFLATED)
 
-  property_files = StreamingPropertyFiles()
-
   # Write the current metadata entry with placeholders.
-  metadata['ota-streaming-property-files'] = property_files.Compute(output_zip)
+  for property_files in needed_property_files:
+    metadata[property_files.name] = property_files.Compute(output_zip)
   WriteMetadata(metadata, output_zip)
   common.ZipClose(output_zip)
 
@@ -1122,14 +1140,14 @@
 
   # Open the signed zip. Compute the final metadata that's needed for streaming.
   with zipfile.ZipFile(prelim_signing, 'r') as prelim_signing_zip:
-    expected_length = len(metadata['ota-streaming-property-files'])
-    metadata['ota-streaming-property-files'] = property_files.Finalize(
-        prelim_signing_zip, expected_length)
+    for property_files in needed_property_files:
+      metadata[property_files.name] = property_files.Finalize(
+          prelim_signing_zip, len(metadata[property_files.name]))
 
   # Replace the METADATA entry.
   common.ZipDelete(prelim_signing, METADATA_NAME)
-  output_zip = zipfile.ZipFile(prelim_signing, 'a',
-                               compression=zipfile.ZIP_DEFLATED)
+  output_zip = zipfile.ZipFile(
+      prelim_signing, 'a', compression=zipfile.ZIP_DEFLATED)
   WriteMetadata(metadata, output_zip)
   common.ZipClose(output_zip)
 
@@ -1138,8 +1156,8 @@
 
   # Reopen the final signed zip to double check the streaming metadata.
   with zipfile.ZipFile(output_file, 'r') as output_zip:
-    property_files.Verify(
-        output_zip, metadata['ota-streaming-property-files'].strip())
+    for property_files in needed_property_files:
+      property_files.Verify(output_zip, metadata[property_files.name].strip())
 
 
 def WriteBlockIncrementalOTAPackage(target_zip, source_zip, output_zip):
@@ -1555,7 +1573,10 @@
   # FinalizeMetadata().
   common.ZipClose(output_zip)
 
-  FinalizeMetadata(metadata, staging_file, output_file)
+  needed_property_files = (
+      StreamingPropertyFiles(),
+  )
+  FinalizeMetadata(metadata, staging_file, output_file, needed_property_files)
 
 
 def main(argv):
diff --git a/tools/releasetools/test_ota_from_target_files.py b/tools/releasetools/test_ota_from_target_files.py
index c8e87bf..e2e85fd 100644
--- a/tools/releasetools/test_ota_from_target_files.py
+++ b/tools/releasetools/test_ota_from_target_files.py
@@ -26,8 +26,8 @@
     _LoadOemDicts, BuildInfo, GetPackageMetadata,
     GetTargetFilesZipForSecondaryImages,
     GetTargetFilesZipWithoutPostinstallConfig,
-    Payload, PayloadSigner, POSTINSTALL_CONFIG, StreamingPropertyFiles,
-    WriteFingerprintAssertion)
+    Payload, PayloadSigner, POSTINSTALL_CONFIG, PropertyFiles,
+    StreamingPropertyFiles, WriteFingerprintAssertion)
 
 
 def construct_target_files(secondary=False):
@@ -590,7 +590,23 @@
       self.assertNotIn(POSTINSTALL_CONFIG, verify_zip.namelist())
 
 
-class StreamingPropertyFilesTest(unittest.TestCase):
+class TestPropertyFiles(PropertyFiles):
+  """A class that extends PropertyFiles for testing purpose."""
+
+  def __init__(self):
+    super(TestPropertyFiles, self).__init__()
+    self.name = 'ota-test-property-files'
+    self.required = (
+        'required-entry1',
+        'required-entry2',
+    )
+    self.optional = (
+        'optional-entry1',
+        'optional-entry2',
+    )
+
+
+class PropertyFilesTest(unittest.TestCase):
 
   def tearDown(self):
     common.Cleanup()
@@ -607,7 +623,7 @@
     return zip_file
 
   @staticmethod
-  def _parse_streaming_metadata_string(data):
+  def _parse_property_files_string(data):
     result = {}
     for token in data.split(','):
       name, info = token.split(':', 1)
@@ -627,47 +643,57 @@
 
   def test_Compute(self):
     entries = (
-        'payload.bin',
-        'payload_properties.txt',
+        'required-entry1',
+        'required-entry2',
     )
     zip_file = self._construct_zip_package(entries)
-    property_files = StreamingPropertyFiles()
+    property_files = TestPropertyFiles()
     with zipfile.ZipFile(zip_file, 'r') as zip_fp:
-      streaming_metadata = property_files.Compute(zip_fp)
+      property_files_string = property_files.Compute(zip_fp)
 
-    tokens = self._parse_streaming_metadata_string(streaming_metadata)
+    tokens = self._parse_property_files_string(property_files_string)
     self.assertEqual(3, len(tokens))
     self._verify_entries(zip_file, tokens, entries)
 
-  def test_Compute_withCareMapTxtAndCompatibilityZip(self):
+  def test_Compute_withOptionalEntries(self):
     entries = (
-        'payload.bin',
-        'payload_properties.txt',
-        'care_map.txt',
-        'compatibility.zip',
+        'required-entry1',
+        'required-entry2',
+        'optional-entry1',
+        'optional-entry2',
     )
     zip_file = self._construct_zip_package(entries)
-    property_files = StreamingPropertyFiles()
+    property_files = TestPropertyFiles()
     with zipfile.ZipFile(zip_file, 'r') as zip_fp:
-      streaming_metadata = property_files.Compute(zip_fp)
+      property_files_string = property_files.Compute(zip_fp)
 
-    tokens = self._parse_streaming_metadata_string(streaming_metadata)
+    tokens = self._parse_property_files_string(property_files_string)
     self.assertEqual(5, len(tokens))
     self._verify_entries(zip_file, tokens, entries)
 
+  def test_Compute_missingRequiredEntry(self):
+    entries = (
+        'required-entry2',
+    )
+    zip_file = self._construct_zip_package(entries)
+    property_files = TestPropertyFiles()
+    with zipfile.ZipFile(zip_file, 'r') as zip_fp:
+      self.assertRaises(KeyError, property_files.Compute, zip_fp)
+
   def test_Finalize(self):
     entries = [
-        'payload.bin',
-        'payload_properties.txt',
+        'required-entry1',
+        'required-entry2',
         'META-INF/com/android/metadata',
     ]
     zip_file = self._construct_zip_package(entries)
-    property_files = StreamingPropertyFiles()
+    property_files = TestPropertyFiles()
     with zipfile.ZipFile(zip_file, 'r') as zip_fp:
+      # pylint: disable=protected-access
       raw_metadata = property_files._GetPropertyFilesString(
           zip_fp, reserve_space=False)
       streaming_metadata = property_files.Finalize(zip_fp, len(raw_metadata))
-    tokens = self._parse_streaming_metadata_string(streaming_metadata)
+    tokens = self._parse_property_files_string(streaming_metadata)
 
     self.assertEqual(3, len(tokens))
     # 'META-INF/com/android/metadata' will be key'd as 'metadata' in the
@@ -677,15 +703,17 @@
 
   def test_Finalize_assertReservedLength(self):
     entries = (
-        'payload.bin',
-        'payload_properties.txt',
-        'care_map.txt',
+        'required-entry1',
+        'required-entry2',
+        'optional-entry1',
+        'optional-entry2',
         'META-INF/com/android/metadata',
     )
     zip_file = self._construct_zip_package(entries)
-    property_files = StreamingPropertyFiles()
+    property_files = TestPropertyFiles()
     with zipfile.ZipFile(zip_file, 'r') as zip_fp:
       # First get the raw metadata string (i.e. without padding space).
+      # pylint: disable=protected-access
       raw_metadata = property_files._GetPropertyFilesString(
           zip_fp, reserve_space=False)
       raw_length = len(raw_metadata)
@@ -710,15 +738,99 @@
 
   def test_Verify(self):
     entries = (
+        'required-entry1',
+        'required-entry2',
+        'optional-entry1',
+        'optional-entry2',
+        'META-INF/com/android/metadata',
+    )
+    zip_file = self._construct_zip_package(entries)
+    property_files = TestPropertyFiles()
+    with zipfile.ZipFile(zip_file, 'r') as zip_fp:
+      # First get the raw metadata string (i.e. without padding space).
+      # pylint: disable=protected-access
+      raw_metadata = property_files._GetPropertyFilesString(
+          zip_fp, reserve_space=False)
+
+      # Should pass the test if verification passes.
+      property_files.Verify(zip_fp, raw_metadata)
+
+      # Or raise on verification failure.
+      self.assertRaises(
+          AssertionError, property_files.Verify, zip_fp, raw_metadata + 'x')
+
+
+class StreamingPropertyFilesTest(PropertyFilesTest):
+  """Additional sanity checks specialized for StreamingPropertyFiles."""
+
+  def test_init(self):
+    property_files = StreamingPropertyFiles()
+    self.assertEqual('ota-streaming-property-files', property_files.name)
+    self.assertEqual(
+        (
+            'payload.bin',
+            'payload_properties.txt',
+        ),
+        property_files.required)
+    self.assertEqual(
+        (
+            'care_map.txt',
+            'compatibility.zip',
+        ),
+        property_files.optional)
+
+  def test_Compute(self):
+    entries = (
         'payload.bin',
         'payload_properties.txt',
         'care_map.txt',
+        'compatibility.zip',
+    )
+    zip_file = self._construct_zip_package(entries)
+    property_files = StreamingPropertyFiles()
+    with zipfile.ZipFile(zip_file, 'r') as zip_fp:
+      property_files_string = property_files.Compute(zip_fp)
+
+    tokens = self._parse_property_files_string(property_files_string)
+    self.assertEqual(5, len(tokens))
+    self._verify_entries(zip_file, tokens, entries)
+
+  def test_Finalize(self):
+    entries = [
+        'payload.bin',
+        'payload_properties.txt',
+        'care_map.txt',
+        'compatibility.zip',
+        'META-INF/com/android/metadata',
+    ]
+    zip_file = self._construct_zip_package(entries)
+    property_files = StreamingPropertyFiles()
+    with zipfile.ZipFile(zip_file, 'r') as zip_fp:
+      # pylint: disable=protected-access
+      raw_metadata = property_files._GetPropertyFilesString(
+          zip_fp, reserve_space=False)
+      streaming_metadata = property_files.Finalize(zip_fp, len(raw_metadata))
+    tokens = self._parse_property_files_string(streaming_metadata)
+
+    self.assertEqual(5, len(tokens))
+    # 'META-INF/com/android/metadata' will be key'd as 'metadata' in the
+    # streaming metadata.
+    entries[4] = 'metadata'
+    self._verify_entries(zip_file, tokens, entries)
+
+  def test_Verify(self):
+    entries = (
+        'payload.bin',
+        'payload_properties.txt',
+        'care_map.txt',
+        'compatibility.zip',
         'META-INF/com/android/metadata',
     )
     zip_file = self._construct_zip_package(entries)
     property_files = StreamingPropertyFiles()
     with zipfile.ZipFile(zip_file, 'r') as zip_fp:
       # First get the raw metadata string (i.e. without padding space).
+      # pylint: disable=protected-access
       raw_metadata = property_files._GetPropertyFilesString(
           zip_fp, reserve_space=False)