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Re: RDF datatyping summary

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 21 Nov 2002 08:34:03 -0500 (EST)
Message-Id: <20021121.083403.28198727.pfps@research.bell-labs.com>
To: jjc@hplb.hpl.hp.com
Cc: www-webont-wg@w3.org

[It is hard to reply in-line to an HTML document. :-(]


> <h2><a name=3D"value">What is the value?</a></h2>
> <p>
> See 
> <a href=3D"http://www.w3.org/TR/rdf-concepts/#section-Literal-Value">RDF Concepts</a>
> and/or
> <a href=3D"http://www.w3.org/TR/2002/WD-rdf-mt-20021112/#dtype_interp">RDF Semantics</a>.
> </p>
> <p>
> The value associated with a typed literal is found by applying the datatype 
> mapping associated with the datatype URI to the lexical form. 
> </p>

Except for rdf:XMLLiteral.

> <p>If the lexical form is not in the lexical space, then this is in error (semantically
> but not syntactically). (The literal is not
> well-formed).
> The model theoretic treatment of errors is complicated (see below).

Calling this an error is misleading, in my opinion.  An invalid literal
just denotes some junk value.


> <h2><a name=3D"webont">Webont specific issues</a></h2>
> <p>
> At least in the RDF world, the decision that literals are
> resources makes the separation of datatyped and object properties harder.

Somewhat harder, but not too much harder. 

> I believe this is a non-issue given the way OWL DL is defined.
> I have produced an 
> <a href=3D"http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Nov/0055.html">
> awkward test case</a> based on there being only two boolean values
> (Patrick Stickler summed up "Yes, I agree that the entailment holds.
> No, I don't think it is very useful as a test case.").

On the contrary, this is precisely the sort of thing that makes a useful
test case.  It is an entailment that can easily be missed by implementors.

> The difficulty of defining new datatypes with URIs is a problem e.g.
> <a href=3D"http://www.w3.org/TR/owl-guide/#Datatypes1">the wine year</a>
> examples in the guide are nonstandard, and do not appear to be fixable.

Well, I don't see why this is non-fixable.  WebOnt could just state
something like

	A datatype URI that is a fragment in an XML Schema document refers
	to the top-level simple datatype with that fragment as its local
	name, if any.


Received on Thursday, 21 November 2002 08:35:30 UTC

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