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Re: Type-assignment (was Re: Are we losing out because of grammars?)

James Clark wrote:
> Yes, indeed. ID/IDREF is a very interesting problem for TREX. However,
> although type-assignment can be used to deal with this, it's not quite
> solving the right problem.  For ID/IDREF, I want to know whether I can
> assign datatypes unambiguously not whether I can assign labels (in the
> RELAX sense) umabiguously.  A grammar may be ambiguous with respect to
> assignment of labels, but unambiguous with respect to assignement of
> datatypes.

To distinguish the two types of ambiguity, we need two terms.  How about  
ambiguity of datatype assignment and ambiguity of interpretation?

Kawaguchi-san's algorithm for detecting ambiguity of interpretation looks 
cool.  Is it possible to detect ambiguity of datatype assignment by 
examining a TREX pattern?
> My current thinking is that the ID/IDREF approach to uniqueness
> constraints doesn't really scale. For example, there's no way I can see
> to make it handle multipart keys. ID isn't purely a datatype in the same
> way that NMTOKEN is: making an attribute have type ID has side-effects
> on the validity of other attributes that making an attribute have type
> NMTOKEN does not.  

Agreed.  But I do not want to miss ID.  It is so common right now, and 
people would like to use ID as a datatype in writing grammars or schemas.

>I think it's better therefore to move to a completely
> different approach to handling uniquessnes and cross-reference
> constraints, more along the lines of the identity constraints in W3C's
> XML Schemas.

Or, we can use Schematron together with RELAX/TREX.