In the aftermath of #999/the removal of the artifact mediaType, I believe that the guidance for descriptors has become misleading.

Artifacts are now represented using the standard image manifest and mediaType:

When we had a separate mediaType/artifact manifest, the following line in the descriptor specification was informative, as it implies that "images" (read: runnable content) should have a platform, but "artifacts" (arbitrary content) may or may not:

However, now that there is one manifest mediaType, this advice appears to be rather unhelpful; all manifests are now the same type, so this implies that all manifests SHOULD have a platform in their descriptor.

In practice, this has lead to implementations including/believing they should include {"os": "unknown", "architecture": unknown"} when describing non-image content (artifacts), which I believe to be misguided/incorrect, as values for these fields SHOULD be understood by the Go toolchain:

I'd like to drop this line from the descriptor spec, or amend it to acknowledge artifactType, and the config.mediaType fallback (collectively "artifacts"); but between these options I have no strong preference.