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Re: pfps-08 last call comment on typed literals

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 1 May 2003 11:20:48 -0500
Message-Id: <p05210629bad6f3640a30@[10.0.100.12]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-comments@w3.org

>From: pat hayes <phayes@ai.uwf.edu>
>Subject: Re: pfps-08 last call comment on typed literals
>Date: Tue, 29 Apr 2003 16:51:43 -0500
>
>>  Peter,
>>
>>  In
>>
>>  http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0087.html
>>
>>  you raised a last call comment on the RDFCore WD's which was recorded as:
>>
>>  http://www.w3.org/2001/sw/RDFCore/20030123-issues/#pfps-8
>>
>>  The WG has previously decided to reject this comment:
>>
>>  http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0537.html
>>
>>  However, subsequent work has suggested that we reconsider this decision.
>>
>>  The treatment of XML literals currently proposed would retain the
>>  'simple' version (in which the literals are treated as a special
>>  lexical form) in RDF and RDFS interpretations, but treat
>>  rdf:XMLliteral as denoting a datatype object in D-interpretations.
>>
>>  This would support the entailment you refer to in all datatyped
>>  interpretations, for typed literals which do not contain language
>>  tags.  It would not, however, support an inference of the following
>>  form (in Ntriples):
>>
>>  ex:bar owl:sameIndividualAs rdf:XMLLiteral .
>>  ex:s ex:p "foo"@tag^^rdf:XMLLiteral .
>>  |-
>>  ex:s ex:p "foo"@tag^^ex:bar
>>
>>  since the RDF semantic conditions require that language tags are
>>  ignored in non-XML typed literals.
>>
>>  Please let us know whether this would be acceptable.
>>
>>  Pat Hayes
>
>I do not view this as a satisfactory solution to my issue.
>
>I do not even view it as in any way better than the previous state of
>affairs.
>

OK; but that is rather a strong rejection, which leaves me rather at 
a loss how to proceed. In earlier correspondence (off-list) you 
seemed to indicate that you found the current treatment of datatypes 
satisfactory; admittedly at that time our attention had not been 
drawn to the above case.  There seem to be many ways that OWL could 
accommodate to this situation. For example, I gather than Webont is 
likely to recommend that rdf:XMLLiteral be deprecated in OWL. If so, 
it would be harmless for OWL to deprecate, or even forbid, the use of 
lang tags in literals (since they play no role anywhere but for 
XMLLiteral) , and then the above would seem to solve the problem you 
raised in your original comment.  Another, less draconian, solution 
would be to forbid any OWL assertion which equates anything to 
rdf:XMLliteral (which, because of its special role in the RDF syntax, 
has to be treated as an opaque identifier rather than a simple name.) 
Such equations would be prohibited in OWL-DL and OWL-Lite, in any 
case.  Your strong rejection, therefore, leads me to believe that 
there might be other problems than the ones I had diagnosed from your 
original comment.

Could you indicate which aspects of this are you are unsatisfied 
with?  In particular, if the treatment of lang tags were made uniform 
across all typed literals, so as to support substitution of equals 
anywhere in the RDF literal syntax in datatyped interpretations, 
would that be sufficient? There are several ways we could try to 
arrange that to happen, but it would save some work if you could tell 
us what your criteria for success would be, so that we can avoid 
unsatisfactory designs by a process more efficient than Darwinian 
selection.  Or would you insist on XML literal typing being done in a 
semantically uniform way between undatatyped and datatyped RDF 
interpretations? I do not think we can accommodate the latter 
requirement, so if that is what you find unsatisfactory then there 
may be no point in attempting to satisfy you on this particular issue.

Pat
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Received on Thursday, 1 May 2003 12:20:53 GMT

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