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Re: RDF Semantics: datatype entailments

From: <herman.ter.horst@philips.com>
Date: Tue, 11 Mar 2003 14:11:18 +0100
To: pat hayes <phayes@ai.uwf.edu>
Cc: www-rdf-comments@w3.org
Message-ID: <OFED2A7C71.AAF06FF1-ON41256CDE.00377551-C1256CE6.00489B67@diamond.philips.com>

>>RDF Semantics document,
>>last call version, 23 january 2003
>>This comment was mailed earlier to the WebOnt WG [1].
>>
>>
>>Section 4.3, Datatype entailments
>>This section only describes closure rules.
>>However, I would like to suggest that more can be said.
>>
>>For each recognized datatype x  (that is, if x is in D)
>>the following triple is D-entailed already by the empty RDF graph:
>>   name(x) rdf:type rdfs:Datatype .
>>
>>This follows from the assumption on D-interpretations that
>>D is a subset of ICEXT(I(rdfs:Datatype)).
>
>Well yes, but there is a circularity here, since the notion of 
>'recognized' only makes sense relative to some assertions of this 
>precise form. 
>That is, one asserts that a datatype is 'recognized' by 
>writing a triple of the form
>
(*) >  name(x) rdf:type rdfs:Datatype .

This intent (?) is not clear from the document.  On the contrary,
the names D-interpretation / D-entailment suggest that the recognized
datatypes (i.e. the datatypes from D) are recognized 
"on the meta level", i.e., that their recognition does not NEED to be 
stated by means of an RDF triple.
Moreover, D-entailment means much more than RDFS-entailment given
as extra input these statements of the form (*), as it incorporates,
for example, the literal-to-value mappings.
Therefore, I interpreted the automatic entailment of these triples (*) 
as a natural feature of the definitions / theory, and would find
it natural to mention it in the document.

>
>so of course, *in all models of this assertion* , this assertion is 
>true, ie entailed by the empty graph. 

When using D-interpretations / D-entailment, the assertion (*) above 
is not only true "*in all models of this assertion*", but also in 
all models of the empty set of assertions, i.e. in all models of
the empty RDF graph.

>While technically correct, this 
>is rather a misleading way of characterizing the situation, seems to 
>me :-)
>
>Pat

>
>
>>Herman ter Horst
>>Philips Research
>>
>>[1] http://lists.w3.org/Archives/Public/www-webont-wg/2003Feb/0313.html
>
>
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Herman
Received on Tuesday, 11 March 2003 08:13:22 GMT

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