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Re: rdfs:Datatype question

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Sat, 2 Nov 2002 13:08:13 +0200
Message-ID: <007d01c28260$22e799b0$2380720a@NOE.Nokia.com>
To: <w3c-rdfcore-wg@w3.org>, "ext pat hayes" <phayes@ai.uwf.edu>

IMO, we need rdfs:Datatype to define the set of classes which
have the required characteristics for RDF datatyping, namely
a lexical space, a value space, and an N:1 mapping from the 
lexical value space where N > 0.

The term rdfs:Datatype is a means to give a name to the set
of RDF Classes which exhibit those characteristics.

Patrick


[Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com]


----- Original Message ----- 
From: "ext pat hayes" <phayes@ai.uwf.edu>
To: <w3c-rdfcore-wg@w3.org>
Sent: 02 November, 2002 04:25
Subject: rdfs:Datatype question


> 
> Er...guys, Something must have been decided over the summer that I 
> missed somehow. As far as I can see, given the decisions we have made 
> about datatyping, there simply is no useful role for rdfs:Datatype. 
> We don't need it, so why have we got it?
> 
> As I understand the current decision, the *only* place that a 
> datatype URI can be used so as to exhibit, as it were, its datatyping 
> potential , is inside a typed literal. We aren't going to have any 
> special datatyping entailments which involve the use of a datatype 
> URI as a property (checked in my last email: consensus apparently 
> that have agreed not to do that); there are no long-range datatyping 
> entailments, for sure, so that there is nothing that can be inferred 
> about any interpretations of literals from any reference to a 
> datatype class (that is, something can be said to be in the class, of 
> course, but the fact that it is a *datatype* class has no particular 
> semantic significance for anything else.) And as far as I can see, 
> there is no way to infer that anything is in a datatype class, since 
> the only things that we know are in those classes are literals, which 
> can't be subjects. So we really don't need to impose any special 
> datatyping conditions at all on the property or class extensions of 
> datatype URIs in any interpretation, even in 
> RDFS-with-datatype-entailment.
> 
> Given this, I can't quite see what Im supposed to say about 
> rdfs:Datatype in the model theory. Like, it's the class of datatypes. 
> But that class isn't defined by RDF(S), and its not even known to 
> RDF(S), so why has RDFS got a special syntax for it? I don't even 
> have any way to refer to it in the MT metalanguage. Time was, when we 
> had datatyping banners unfurled all over the place, that we needed 
> RDFS to be able to 'declare' that some URIref was supposed to be a 
> datatype label, so as to trigger all those range-datatype inferences 
> and so on. But now its obvious from the syntax which urirefs are 
> supposed to be datatypes: the ones inside the typed literals. Saying 
> it in an explicit triple doesn't seem to add anything. And if we say 
> it is, and in fact it isn't (or an RDF engine can't find it) then we 
> are (or the engine is) in just the same pickle as if we had used it 
> inside a typed literal and in fact it isn't. No amount of RDF 
> triple-asserting is going to magically create a non-existent datatype.
> 
> Unless Im missing something, therefore, I propose that we drop rdfs:Datatype.
> 
> PROPOSE: do not introduce rdfs:Datatype into the rdfs namespace.
> 
> Then I can put our very simply boiled-down datatyping into the core 
> RDF MT quite happily, since it won't involve the RDFS vocabulary in 
> any way.  It will just be one extra line in the semantics of 
> literals. And if we do keep it, then (unless I am warned of a mistake 
> in the above), I am just going to say that it is like rdf:List, 
> rdf:seeAlso, rdf:first, rdf:rest, rdf:nil and rdf:comment in having 
> no semantics at all.
> 
> Pat
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Received on Saturday, 2 November 2002 06:08:15 EST

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