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RE: UPDATE: why RDF syntax is not suitable for OWL

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Fri, 15 Feb 2002 20:57:32 -0500
Message-Id: <p05101460b8936aebd3b8@[192.168.0.6]>
To: "Smith, Michael K" <michael.smith@eds.com>
Cc: webont <www-webont-wg@w3.org>
>Thanks, Pat.  That is what I was looking for. At least I understand better
>what's being said. Though it still doesn't quite compute.
>
>The N-Triples doc and the description of graphs in the MT are certainly
>simple.  But from the previous version of the RDF Model and Syntax
>Specification I had thought there were restrictions on the permitted
>triples.  For example, that a predicate must be a Property.

Well, theres an ambiguity here about what "must be" means. Since 
being in an RDFS class is a semantic issue and not a matter of 
syntax, it doesn't make sense to interpret this 'must be' as a 
syntactic restriction. It is a semantic one, which is just another 
way of saying that if you assert a triple

S P O .

then you can *infer*

P rdf:type rdfs:Property .

as indeed you can  (cf. closure rule rdf1 , 
http://www.w3.org/TR/rdf-mt/#rdfsclosdef)

>Not that this example causes a problem for the model theory. 
>If foo is a class and not a property, I(<foo,foo,1>) is false.

True, but I don't see that as a problem. If you assert this, then you 
are saying that it isn't false, which is exactly where the 
'restriction' comes from.

>
>Maybe I just need to wait for these docs to be finished.  If I read the
>referenced decision below it does not specify the single place where the
>syntax of RDF will be defined.

OK, fair enough; that issue is rather cloudy at the moment. The WG is 
working seriously on providing a single coherent overall view of RDFS 
and making sure that the various documents are aligned in terminology 
and, er, attitude. We havn't quite finished yet....

>  The RDF/XML is incomplete in its ability to
>express RDF.  The editor of the RDF Syntax WD will include in that document
>a clear statement of the RDF graph structures that RDF/XML is unable to
>represent.

Right, we know this needs to be done carefully.

>Perhaps as a part of that effort, the RDF Syntax WD will provide
>a complete syntax for RDF triples.

Right.

Pat
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Received on Friday, 15 February 2002 20:57:29 GMT

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