From: pat hayes <phayes@ihmc.us>

Date: Wed, 14 Jan 2004 11:26:04 -0600

Message-Id: <p06001f05bc2b2a068576@[10.0.100.76]>

To: Graham Klyne <GK@ninebynine.org>

Cc: www-rdf-comments@w3.org

Date: Wed, 14 Jan 2004 11:26:04 -0600

Message-Id: <p06001f05bc2b2a068576@[10.0.100.76]>

To: Graham Klyne <GK@ninebynine.org>

Cc: www-rdf-comments@w3.org

>At 22:07 13/01/04 -0600, pat hayes wrote: >>One way to extend this is to require that the class extension of x >>be a *subset* of the value space of x. This seems to be the >>minimal extension which would handle datatype clashes >>appropriately. But now, the finite-value class examples give >>difficulties for completeness arguments, since now the 'boolean' >>example is rejuvenated: >> >>a p "true"^^boolean >>a p "false"^^boolean >>c type boolean >>|= >>a p c >> >>In order to block this, we would need to allow ICEXT(I(boolean)) to >>be a proper superset of the boolean value space. >> >>It can't be both a subset and a proper superset. > >My apologies for not following the debate closely enough, but I'm >not sure what is the problem here. Why would one want to "block" >this entailment? Because such an entailment makes it impractical to have a complete system of rules in the RDF/RDFS style for D-entailment: in effect, it encodes a universal quantification (if p(a true) and p(a false) then forall x if boolean(x) then p(a x) ). One can of course add this as a 'special' rule for xsd:boolean, but then you need a special rule for any finite datatype. One can make out a reasonable case that such universals are alien to the RDF conjunction-existential way of doing things; and Herman noticed that the weaker semantics would allow a completeness result to be obtained. This weaker semantics allows literal type-checking but doesn't handle any kind of 'exclusion' reasoning on datatype classes. I was seduced by the appeal of having a D-entailment lemma, but now see that not being able to recognize type clashes is too high a price to pay. (Pat retires to his corner to lick his wounds.) Pat >#g > > >------------ >Graham Klyne >For email: >http://www.ninebynine.org/#Contact -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ihmc.us http://www.ihmc.us/users/phayesReceived on Wednesday, 14 January 2004 12:26:07 UTC

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