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Re: Type-assignment (was Re: Are we losing out because of grammars?)
- From: "K.Kawaguchi" <firstname.lastname@example.org>
- To: James Clark <email@example.com>
- Date: Fri, 02 Feb 2001 10:22:46 -0800
> 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. 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.
I second you!
> Another interesting issue with ID and with type-assigment is how it
> interacts with intersection (the "concur" operator in TREX). What do I
> do with something like this
Since your example uses <concur>, every attribute "a" must be
considered as ID and there are no other possible interpretation.
Things get tricky if you change <concur> to <choice>. We can't decide
any more whether "a" attribute is ID.
And I guess that what you intended.
> <element name="e">
> <attribute name="a">
> <data type="xsd:ID"/>