The spec requires specifying a version for schemas. I'd like to propose to remove versioning.

Here's how the approach would work:

• Schemas may mutate.
• Mutation to schemas must be backwards compatible (e.g. adding a new field).
• Changes that break backwards compatibility must create a new schema.

The main advantages of a versionless schema spec are:

• Removes the need of a required field.
• No need to do dependency resolution during implementation. (e.g. the question of "is 1.0.3 allowed in the specified 1.0.* ? ")

There are some disadvantages as well:

• You won't be able to specify things like "All schemas of type x between 0.0.1 and 3.0.1 are allowed". I argue that such a disadvantage isn't that bad, because you can have a new schema for all major revisions. In the previous example, it would be "Accept the following schemas: schema_x_v0, schema_x_v1, schema_x_v2, schema_x_v3".

This is similar to approaches taken with REST apis, where the whole api is versioned, but the request schemas aren't.

Would love to hear thoughts. I admit I'm not clear on what the use cases of versioning look like so far, so feedback is more than welcome.