Re: Disjointness of value spaces

Brian McBride <bwm@hplb.hpl.hp.com> writes:

> The RDFCore WG are putting the finishing touches to a proposal for
> using XML Schema Datatypes in RDF graphs.  We hope to have a WD to
> share with folks soon.

Great.

> In doing this, the following question has arisen concerning the value
> spaces of the primitive datatypes.
> 
> 
> Are the value spaces of the primitive datatypes disjoint, i.e. are
> there any cases where a value may be in more than value space.  

Not in the XML Schema REC as published.

> A specific case to consider is:
> 
>    is http://example.org/ in both xsd:string and xsd:anyURI
> 

Disjoint.

> noting that RFC 2396 states:
> 
>    [[An identifier is an object that can act as a reference to
>           something that has identity.  In the case of URI, the object is
>           a sequence of characters with a restricted syntax.]]
> 
> Put another way, can we assume that if we have two values, one from
> the value space of one primitive datatype, and the other from the
> value space of a different primitive datatype, then they must be
> different values.

Yes.

> To the best of my knowledge, the RDFCore WG has no preferred answer to
> this question.  We wish to know the answer to ensure that our
> specification accurately reflects XML Schema datatypes.

We are in fact preparing an erratum to clarify this, as the current
wording is somewhat unclear, and in one respect wrong.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2002, part-time member of W3C Team
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