- A "current version" and a “minimum supported version", which means that this manifest would be a correct representation for a tool supporting “minimum supported version” (but might have some improved capability for later tools, supporting "current version").
The version in this case refers to the version of the schema.
That should indicate what fields are expected to be present, which fields are optional, and what is the semantics of those fields
- A clear rule that says how a tool supporting minimum but not current is to skip the data it does not recognise (and a mechanism for organising content that allows this).
The general expectation, as we discussed on the context of compatibility for the Ecosystem IS, is that if the file has a new revision on the same version, a tool that knows about an older revision should be able to parse that file with the correct semantics while ignoring the fields it doesn't know about.
That limits what kinds of changes can be done to the schema in a revision increment.
If a change is not possible while maintaining that compatibility, then it would need to be a new major version, and therefore the tool that doesn't understand that version will not be able to process the file.
Daniel