Default prefix in RDFa 1.1 Core (Re: Editor's Drafts Updated)

Section 9 says: "RDFa the 'default prefix' mapping is http://www.w3.org/1999/xhtml/vocab#."

First of all, I think this statement is not for RDFa 1.1 Core and should be moved to RDFa 1.1 XHTML. But I begin to wonder how we handle these default prefixes...

My understanding is that this default prefix applies to CURIE-s of the form ':something'. We do have a mechanism now, via @vocab, for CURIE-s of the form 'something'. I wonder whether we should not merge these two notions. (I know this has been discussed before...)

I am also a bit worried for the various language specific things. A specific language can define:

1. default prefix
2. top level @vocab value
3. set of terms and prefixes via a default @profile
4. additional attributes and modification on the processing rules

I am a bit worried about deployment difficulties; how would an implementation follow that? 

Currently the @profile document can only handle #3. I do not think there is really a way to handle #4; my initial reaction is that XML dialect authors should be discouraged to do #4, actually (SVG does not do it, for example).

A possibility is to extend the possibilities of @profile to define @vocab (getting a bit convoluted, though) or #1. Then we could have some sort of a registry that binds, eg, media types to profiles that an implementation can consult regularly...

To be discussed, I suppose...

Ivan

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Ivan Herman, W3C Semantic Web Activity Lead
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