Existing Wording
Resources have multiple representations. A resource is valid if it meets the above rules, and is represented in either XML or JSON according to the rules defined in this specification. Other representations are allowed, but are not described by this specification.

Comments
This statement is ambiguous. If a resource uses another representaton is it valid or not?

Grahame's Comments
Don't know the answer. And I don't think we want to say - we can allow it, but we can't say whether it's valid. Hopefully we can find some wording to clarify this without having to take a further position