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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. Cheers, Makoto
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