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Re: Semantics Spanner

From: Graham Klyne <gk@ninebynine.org>
Date: Fri, 16 May 2003 11:10:21 +0100
Message-Id: <>
To: Jeremy Carroll <jjc@hpl.hp.com>, w3c-rdfcore-wg@w3.org
Cc: pat hayes <phayes@ai.uwf.edu>

Hmm, yes, it seems problematic.  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 xsd:string rdf:type .

2/      xsd:int rdf:type rdfs:Datatype .
                 DOES NOT {<rdf:XMLLiteral,XMLLiteral>,
         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.


At 11:19 16/05/03 +0300, Jeremy Carroll wrote:

>On another list, it has been claimed that the current RDF MT editors draft 
>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
>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.

Graham Klyne
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Friday, 16 May 2003 07:25:16 UTC

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