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Re: Semantics Spanner

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Fri, 16 May 2003 12:58:48 +0100
Message-Id: <5.1.0.14.0.20030516125552.04f8a710@localhost>
To: Graham Klyne <gk@ninebynine.org>, Jeremy Carroll <jjc@hpl.hp.com>, w3c-rdfcore-wg@w3.org
Cc: pat hayes <phayes@ai.uwf.edu>

At 11:10 16/05/2003 +0100, Graham Klyne wrote:

>Hmm, yes, it seems problematic.

Can someone decode the cryptic problem statement and show where the dumb 
entailment comes from.  I haven't spotted it yet, but looking through the 
semantics spec I noticed:


rdfD 4

   ddd rdf:type rdfs:Datatype .
   eee rdf:type rdfs:Datatype .
entails
   ddd rdfs:subClassOf eee .

Seems to me that implies that the values spaces of xsd:string and 
xsd:decimal are identical.

I presume I'm missing something.

Brian

>  In particular, it seems to violate:
>
>[[
>General monotonicity lemma. Suppose that S, S' are sets of RDF graphs with 
>every member of S a subset of some member of S'. Suppose that Y indicates 
>a semantic extension of  X, S X-entails E, and S and E satisfy any 
>syntactic restrictions of Y. Then S' Y-entails E.
>
>In particular, if D' is a datatype map and D a subset of D' then if S 
>D-entails E it also S D'-entails E, provided that S and E both recognize 
>all the datatype urirefs in the domain of D'.
>]]
>-- http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-mt-20030117/#dtype_interp
>
>There is also some wording nearby about entailments of inconsistent
>
>Imposing a syntactic constraint on a D-interpretation allowing
>   x rdf:type rdfs:Datatype .
>only if I(x) in D might help, since that would render the antcedent of 
>Peter's  first entailment syntactically invalid.
>
>[[
>1/      xsd:int rdf:type rdfs:Datatype .
>                 {<rdf:XMLLiteral,XMLLiteral>}-entails
>         rdf:XMLLiteral xsd:string rdf:type .
>
>2/      xsd:int rdf:type rdfs:Datatype .
>                 DOES NOT {<rdf:XMLLiteral,XMLLiteral>,
>                 <rdf:int,int>}-entail
>         xsd:string rdf:XMLLiteral rdf:type .
>]]
>-- http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0276.html
>
>
>But there's still a question of such statements in non datatyped 
>interpretations.  I think that's not a problem because there's no 
>constraint there that:
>   x rdf:type rdfs:Datatype .
>is false in all such interpretations, so the first entailment would not hold.
>
>#g
>--
>
>At 11:19 16/05/03 +0300, Jeremy Carroll wrote:
>
>
>>On another list, it has been claimed that the current RDF MT editors 
>>draft has
>>non-monotonic datatyping.
>>If this is the case then it should be fixed.
>>
>>I will try and review this claim before the telecon today, I suggest others
>>might like to as well.
>>
>>The claim is that when foo is not a supported datatype then
>>
>>foo rdf:type rdfs:Datatype .
>>
>>is inconsistent, and hence entails everything.
>>
>>Thus, supporting an additional datatype foo, negates previously valid
>>entailments, and hence causes a datatyped system to layer non-monotonically
>>on top of a datatyped system.
>>
>>I personally find this a credible critique that should be taken seriously.
>>We may need to leave open any semantics issues affected :(
>>
>>The (cryptic) examples given in
>>http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0276.html
>>
>>concern the minimal datatype system consisting of only rdf:XMLLiteral, and so
>>xsd:int plays the role of foo above.
>>
>>I note that this comment is based on the shadow space draft rather than Pat's
>>master copy - we may hope that magic has happened.
>>
>>Jeremy
>
>-------------------
>Graham Klyne
><GK@NineByNine.org>
>PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Friday, 16 May 2003 07:58:45 EDT

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