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Re: RDF should allow XML datatypes

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 29 Oct 2002 14:57:43 +0000
To: Jonathan Borden <jonathan@openhealth.org>
cc: www-rdf-comments <www-rdf-comments@w3.org>, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Message-ID: <2539.1035903463@hoth.ilrt.bris.ac.uk>


Not sure who this is addressed to, but it mostly deals with syntax,
so I'll reply.  The RDF concepts and abstract syntax editors may also
have some comments I expect.


>>>Jonathan Borden said:
> 
> RDF datatyping should allow the form:

This is asking for a feature by showing you think it should be
implemented, which isn't a good way to approach it.

You are obliquely refering to the requirements of WebOnt I assume,
and in particular, 4.3 as recorded in:
  http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I4.3-Structured-Datatypes

which I note, says: "Status Postponed"


> http://example.org#foo http://example.org#prop "<this>is some structured XML</this>"^^http://example.org/SomeSchema#myType
> 
> where http://example.org/SomeSchema#myType identifies the XML datatype:
> element this{text}
> 
> Similarly RDF/XML should provide for:
> 
> <rdf:Description rdf:about="http://example.org#foo">
>     <ex:prop rdf:datatype="http://example.org/SomeSchema#myType">
>             <this>is some structured XML</this>
>     </ex:prop>
> </rdf:Description>
> 
> 
> 1. There is no compelling reason to prohibit this given the current RDF
> datatyping solution for which this is a minor modification to the syntax.

As editor of the RDF/XML spec, I feel this is not a minor syntax
change and in particular does not match our abstract syntax for
datatyped literals, so would require a change to RDF.


> 2. Allowing this will be very useful for OWL which needs to deal with
> structured datatypes

"Postponed"?  Plus you can still do it with the rdf:datatype, since
it allows any lexical form to be given as a string, that includes XML
infosets serialised to a string.


> 3. Despite the face that XML Schema does not _automatically_ provide for
> URIs for schema particles, when it does in the future, and when one
> explicitly assigns a URIref to an XML Schema particle, this solution will be
> most useful.

Knowing that such W3C XML Schema (WXS) datatypes would have URIs,
that's one reason why we use them to identify the datatypes, the
atomic ones in particular.

> 3a. The failure of XML Schema to provide URIs should not arbitrarily limit
> RDF datatypes. Indeed such a failure will arbitrarily limit future RDF and
> XML Schema datatype interoperability
> -- 2 specifications would need to be fixed not just one -- both the current
> XML Schema REC and the new RDF REC
> -- there wouldn't be so much reason for XML Schema to provide URIs for
> complex datatypes since RDF wouldn't be able to use them.

Not sure why you are telling RDF Core this - it's more of a criticism
of WXS, which you should address to the appropriate WG.

RDF and the XML syntax RDF/XML does allow any datatype that has a URI
for its terms and a lexical form that is a string.  A dataype that
has no URI isn't going to work in RDF.

That lexical form could be a serialisation of a structured form such
as vCard, iCalendar, or even XML.  The latter is how you can do
structured XML datatype values in RDF/XML (as revised) if you wish.

Dave
Received on Tuesday, 29 October 2002 10:00:48 GMT

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