diff --git a/metadata/OWNERS b/metadata/OWNERS
new file mode 100644
index 0000000000..6ef81e8880
--- /dev/null
+++ b/metadata/OWNERS
@@ -0,0 +1,6 @@
+# Software Supply Chain Integrity/SBOM
+aredulla@google.com
+dlf@google.com
+jsca@google.com
+renewitt@google.com
+sumakasa@google.com
diff --git a/metadata/fields/known.py b/metadata/fields/known.py
new file mode 100644
index 0000000000..825e96a1b9
--- /dev/null
+++ b/metadata/fields/known.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+# Copyright 2023 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import sys
+from typing import Union
+
+_THIS_DIR = os.path.abspath(os.path.dirname(__file__))
+# The repo's root directory.
+_ROOT_DIR = os.path.abspath(os.path.join(_THIS_DIR, "..", ".."))
+
+# Add the repo's root directory for clearer imports.
+sys.path.insert(0, _ROOT_DIR)
+
+import metadata.fields.types as field_types
+
+# Freeform text fields.
+NAME = field_types.FreeformTextField("Name")
+SHORT_NAME = field_types.FreeformTextField("Short Name")
+REVISION = field_types.FreeformTextField("Revision")
+DESCRIPTION = field_types.FreeformTextField("Description", one_liner=False)
+LOCAL_MODIFICATIONS = field_types.FreeformTextField("Local Modifications",
+                                                    one_liner=False)
+
+# Yes/no fields.
+SECURITY_CRITICAL = field_types.YesNoField("Security Critical")
+SHIPPED = field_types.YesNoField("Shipped")
+LICENSE_ANDROID_COMPATIBLE = field_types.YesNoField(
+    "License Android Compatible")
+
+ALL_FIELDS = (
+    NAME,
+    SHORT_NAME,
+    REVISION,
+    SECURITY_CRITICAL,
+    SHIPPED,
+    LICENSE_ANDROID_COMPATIBLE,
+    DESCRIPTION,
+    LOCAL_MODIFICATIONS,
+)
+ALL_FIELD_NAMES = {field.get_name() for field in ALL_FIELDS}
+FIELD_MAPPING = {field.get_name().lower(): field for field in ALL_FIELDS}
+
+
+def get_field(label: str) -> Union[field_types.MetadataField, None]:
+  return FIELD_MAPPING.get(label.lower())
diff --git a/metadata/fields/types.py b/metadata/fields/types.py
new file mode 100644
index 0000000000..b9dd249101
--- /dev/null
+++ b/metadata/fields/types.py
@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+# Copyright 2023 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import re
+import sys
+from typing import Union
+
+_THIS_DIR = os.path.abspath(os.path.dirname(__file__))
+# The repo's root directory.
+_ROOT_DIR = os.path.abspath(os.path.join(_THIS_DIR, "..", ".."))
+
+# Add the repo's root directory for clearer imports.
+sys.path.insert(0, _ROOT_DIR)
+
+import metadata.fields.util as util
+import metadata.validation_result as vr
+
+# Pattern used to check if the entire string is either "yes" or "no",
+# case-insensitive.
+_PATTERN_YES_OR_NO = re.compile(r"^(yes|no)$", re.IGNORECASE)
+
+# Pattern used to check if the string starts with "yes" or "no",
+# case-insensitive. e.g. "No (test only)", "Yes?"
+_PATTERN_STARTS_WITH_YES_OR_NO = re.compile(r"^(yes|no)", re.IGNORECASE)
+
+
+class MetadataField:
+  """Base class for all metadata fields."""
+  def __init__(self, name: str, one_liner: bool = True):
+    self._name = name
+    self._one_liner = one_liner
+
+  def get_name(self):
+    return self._name
+
+  def validate(self, value: str) -> Union[vr.ValidationResult, None]:
+    """Checks the given value is acceptable for the field.
+
+    Raises: NotImplementedError if called. This method must be overridden with
+    the actual validation of the field.
+    """
+    raise NotImplementedError(f"{self._name} field validation not defined.")
+
+
+class FreeformTextField(MetadataField):
+  """Field where the value is freeform text."""
+  def validate(self, value: str) -> Union[vr.ValidationResult, None]:
+    """Checks the given value has at least one non-whitespace character."""
+    if util.is_empty(value):
+      return vr.ValidationError(f"{self._name} is empty.")
+
+    return None
+
+
+class YesNoField(MetadataField):
+  """Field where the value must be yes or no."""
+  def __init__(self, name: str):
+    super().__init__(name=name, one_liner=True)
+
+  def validate(self, value: str) -> Union[vr.ValidationResult, None]:
+    """Checks the given value is either yes or no."""
+    if util.matches(_PATTERN_YES_OR_NO, value):
+      return None
+
+    if util.matches(_PATTERN_STARTS_WITH_YES_OR_NO, value):
+      return vr.ValidationWarning(
+          f"{self._name} is '{value}' - should be only {util.YES} or {util.NO}."
+      )
+
+    return vr.ValidationError(
+        f"{self._name} is '{value}' - must be {util.YES} or {util.NO}.")
diff --git a/metadata/fields/util.py b/metadata/fields/util.py
new file mode 100644
index 0000000000..1a05661d98
--- /dev/null
+++ b/metadata/fields/util.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+# Copyright 2023 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import re
+from typing import List
+
+# Preferred values for yes/no fields (i.e. all lowercase).
+YES = "yes"
+NO = "no"
+
+# Pattern used to check if the entire string is "unknown", case-insensitive.
+_PATTERN_UNKNOWN = re.compile(r"^unknown$", re.IGNORECASE)
+
+# Pattern used to check if the entire string is functionally empty, i.e.
+# empty string, or all characters are only whitespace.
+_PATTERN_ONLY_WHITESPACE = re.compile(r"^\s*$")
+
+
+def matches(pattern: re.Pattern, value: str) -> bool:
+  """Returns whether the value matches the pattern."""
+  return pattern.match(value) is not None
+
+
+def is_empty(value: str) -> bool:
+  """Returns whether the value is functionally empty."""
+  return matches(_PATTERN_ONLY_WHITESPACE, value)
+
+
+def is_unknown(value: str) -> bool:
+  """Returns whether the value is 'unknown' (case insensitive)."""
+  return matches(_PATTERN_UNKNOWN, value)
+
+
+def quoted(values: List[str]) -> str:
+  """Returns a string of the given values, each being individually quoted."""
+  return ", ".join([f"'{entry}'" for entry in values])
diff --git a/metadata/tests/fields_test.py b/metadata/tests/fields_test.py
new file mode 100644
index 0000000000..d0736e01f1
--- /dev/null
+++ b/metadata/tests/fields_test.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env vpython3
+# Copyright (c) 2023 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import sys
+from typing import List
+import unittest
+
+_THIS_DIR = os.path.abspath(os.path.dirname(__file__))
+# The repo's root directory.
+_ROOT_DIR = os.path.abspath(os.path.join(_THIS_DIR, "..", ".."))
+
+# Add the repo's root directory for clearer imports.
+sys.path.insert(0, _ROOT_DIR)
+
+import metadata.fields.types as field_types
+import metadata.validation_result as vr
+
+
+class FieldValidationTest(unittest.TestCase):
+  def _run_field_validation(self,
+                            field: field_types.MetadataField,
+                            valid_values: List[str],
+                            error_values: List[str],
+                            warning_values: List[str] = []):
+    """Helper to run a field's validation for different values."""
+    for value in valid_values:
+      self.assertIsNone(field.validate(value))
+
+    for value in error_values:
+      self.assertIsInstance(field.validate(value), vr.ValidationError)
+
+    for value in warning_values:
+      self.assertIsInstance(field.validate(value), vr.ValidationWarning)
+
+  def test_freeform_text_validation(self):
+    # Check validation of a freeform text field that should be on one line.
+    self._run_field_validation(
+        field=field_types.FreeformTextField("Freeform single", one_liner=True),
+        valid_values=["Text on single line", "a", "1"],
+        error_values=["", "\n", " "],
+    )
+
+    # Check validation of a freeform text field that can span multiple lines.
+    self._run_field_validation(
+        field=field_types.FreeformTextField("Freeform multi", one_liner=False),
+        valid_values=[
+            "This is text spanning multiple lines:\n"
+            "    * with this point\n"
+            "    * and this other point",
+            "Text on single line",
+            "a",
+            "1",
+        ],
+        error_values=["", "\n", " "],
+    )
+
+  def test_yes_no_field_validation(self):
+    self._run_field_validation(
+        field=field_types.YesNoField("Yes/No test"),
+        valid_values=["yes", "no", "No", "YES"],
+        error_values=["", "\n", "Probably yes"],
+        warning_values=["Yes?", "not"],
+    )
+
+
+if __name__ == "__main__":
+  unittest.main()
diff --git a/metadata/validation_result.py b/metadata/validation_result.py
new file mode 100644
index 0000000000..7d7566025a
--- /dev/null
+++ b/metadata/validation_result.py
@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+# Copyright 2023 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import textwrap
+from typing import Dict, Union
+
+
+class ValidationResult:
+  """Base class for validation issues."""
+  def __init__(self, message: str, fatal: bool, **tags: Dict[str, str]):
+    self._fatal = fatal
+    self._message = message
+    self._tags = tags
+
+  def __str__(self) -> str:
+    prefix = "ERROR" if self._fatal else "[non-fatal]"
+    return f"{prefix} - {self._message}"
+
+  def __repr__(self) -> str:
+    return str(self)
+
+  def is_fatal(self) -> bool:
+    return self._fatal
+
+  def set_tag(self, tag: str, value: str) -> bool:
+    self._tags[tag] = value
+
+  def get_tag(self, tag: str) -> Union[str, None]:
+    return self._tags.get(tag)
+
+  def get_all_tags(self) -> Dict[str, str]:
+    return dict(self._tags)
+
+  def get_message(self, width: int = 0) -> str:
+    if width > 0:
+      return textwrap.fill(text=self._message, width=width)
+
+    return self._message
+
+
+class ValidationError(ValidationResult):
+  """Fatal validation issue. Presubmit should fail."""
+  def __init__(self, message: str, **tags: Dict[str, str]):
+    super().__init__(message=message, fatal=True, **tags)
+
+
+class ValidationWarning(ValidationResult):
+  """Non-fatal validation issue. Presubmit should pass."""
+  def __init__(self, message: str, **tags: Dict[str, str]):
+    super().__init__(message=message, fatal=False, **tags)