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Extensibility
Implementations that are reading/processing manifests or image indexes MUST NOT generate an error if they encounter an unknown property. Instead they MUST ignore unknown properties.
Canonicalization
OCI Images are content-addressable. One benefit of content-addressable storage is easy deduplication. Many images might depend on a particular layer, but there will only be one blob in the store. With a different serialization, that same semantic layer would have a different hash, and if both versions of the layer are referenced there will be two blobs with the same semantic content. To allow efficient storage, implementations serializing content for blobs SHOULD use a canonical serialization. This increases the chance that different implementations can push the same semantic content to the store without creating redundant blobs.
JSON
JSON content SHOULD be serialized as canonical JSON.
Of the OCI Image Format Specification media types, all the types ending in +json contain JSON content.
Implementations:
- Go: github.com/docker/go, which claims to implement canonical JSON except for Unicode normalization.