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Re: pfps-08 last call comment on typed literals

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 20 Mar 2003 16:29:37 -0500 (EST)
Message-Id: <20030320.162937.84275006.pfps@research.bell-labs.com>
To: bwm@hplb.hpl.hp.com
Cc: www-rdf-comments@w3.org

From: Brian McBride <bwm@hplb.hpl.hp.com>
Subject: Fwd: pfps-08 last call comment on typed literals
Date: Thu, 20 Mar 2003 19:41:32 +0000

>Date: Thu, 20 Mar 2003 18:56:18 +0000
>To: pfps@research.bell-labs.com, www-rdf-comments@w3.org
>From: Brian McBride <bwm@hplb.hpl.hp.com>
>Subject: pfps-08 last call comment on typed literals
>
>Peter,
>
>You made a last call comment "Comment on Last Call Working Draft of RDF 
>Semantics document concerning typed literals" captured in
>
  http://www.w3.org/2001/sw/RDFCore/20030123-issues/#pfps-08
>
>After due consideration, the RDFCore WG has resolved
>
>[[RDFCore do not accept this comment. The semantics are as intended.  The 
>text has been clarified to make this clearer.]]
>
  http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Mar/0124.html
>
>
>Please reply to this email, copying www-rdf-comments@w3.org indicating 
>whether this decision is acceptable.
>
>Brian McBride
 

I do not view this reponse as acceptable because it does not point to the
clarification text.  There may also remain outstanding action items related
to this issue (namely pointing to Pat's message(s)).

   http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Mar/0124.html
 >
 >
 >Please reply to this email, copying www-rdf-comments@w3.org indicating
 >whether this decision is acceptable.
 >
 >Brian McBride


I also do not view this response as acceptable for technical reasons:

1/

 From http://www.w3.org/TR/2003/WD-rdf-mt-20030123/

In an RDFS interpretation I (see section 3.3)
         I(rdf:XMLLiteral) in ICEXT(I(rdfs:Datatype))
In a D-interpretation, for any D (see Section 3.4)
         ICEXT(I(rdfs:Datatype)) = D

Therefore, in any D-interpretation, for any D, there must be a member of D
that is a standard datatype corresponding to rdf:XMLLiteral.

This means that any set of datatypes includes a datatype for
rdf:XMLLiteral, and this datatype has a L2V mapping that takes lexical
forms (in the form of strings *without* language tags) to resources.
Any specification of D-interpretations must include this mapping.

This superfluous mapping cannot be accessed from RDF, but can in OWL, for
example by

         rdf:XMLLiteral owl:sameIndividualAs ex:foo .
         ex:bar ex:baz "55"^^ex:foo .

I do not view this as an acceptable situation, if only for semantic
cleanliness reasons.

This situation is not improved in the current editor's draft.

2/

Even if this issue were to be solved, I believe that OWL should have the
following sort of entailment hold:

         rdf:XMLLiteral owl:sameIndividualAs ex:foo .
         _:x owl:sameIndividualAs "..."@en^^rdf:XMLLiteral .
         _:y owl:sameIndividualAs "..."@en^^ex:foo .

entails

         _:x owl:sameIndividualAs _:y .

(This entailment holds for every URI reference except rdf:XMLLiteral.)

However, there is no way for OWL to do this, because typed literals that
include ex:foo are interpreted by the rules for non-built-in datatypes and
there is no way to specify a non-built-in datatype that works the same way
as rdf:XMLLiteral.

I do not view this as an acceptable situation.


Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies
Received on Thursday, 20 March 2003 16:29:51 GMT

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