Merge pull request opencontainers#526 from wking/dry-annotations

considerations: DRY extensibility

Author: vbatts

Makefile

@@ -30,7 +30,7 @@ DOC_FILES := \
 	layer.md \
 	config.md \
 	annotations.md \
-	canonicalization.md
+	considerations.md
 
 FIGURE_FILES := \
 	img/media-types.png

canonicalization.md renamed to considerations.md

@@ -1,3 +1,8 @@
+# Extensibility
+
+Implementations that are reading/processing [manifests](manifest.md) or [manifest lists](manifest-list.md) MUST NOT generate an error if they encounter an unknown property.
+Instead they MUST ignore unknown properties.
+
 # Canonicalization
 
 OCI Images [are](descriptor.md) [content-addressable](image-layout.md).

manifest-list.md

@@ -71,10 +71,6 @@ For the media type(s) that this document is compatible with, see the [matrix][ma
 
     See [Pre-Defined Annotation Keys](annotations.md#pre-defined-annotation-keys).
 
-### Extensibility
-Implementations that are reading/processing manifest lists MUST NOT generate an error if they encounter an unknown property.
-Instead they MUST ignore unknown properties.
-
 ## Example Manifest List
 
 *Example showing a simple manifest list pointing to image manifests for two platforms:*

manifest.md

@@ -66,10 +66,6 @@ Unlike the [Manifest List](manifest-list.md), which contains information about a
 
     See [Pre-Defined Annotation Keys](annotations.md#pre-defined-annotation-keys).
 
-### Extensibility
-Implementations that are reading/processing image manifests MUST NOT generate an error if they encounter an unknown property.
-Instead they MUST ignore unknown properties.
-
 ## Example Image Manifest
 
 *Example showing an image manifest:*

spec.md

@@ -18,7 +18,9 @@ The goal of this specification is to enable the creation of interoperable tools
 - [Filesystem Layers](layer.md)
 - [Image Configuration](config.md)
 - [Annotations](annotations.md)
-- [Canonicalization](canonicalization.md)
+- [Considerations](considerations.md)
+    - [Extensibility](considerations.md#extensibility)
+    - [Canonicalization](considerations.md#canonicalization)
 
 # Notational Conventions