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Re: model theory for RDF/S

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Thu, 27 Sep 2001 22:49:00 -0500
Message-Id: <p0510101db7d9a1be1f18@[205.160.76.184]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-logic@w3.org
>I am concerned that this model theory locks RDF into a particular
>way of interpreting literals, namely that the interpretation of a literal
>can be completely determined from its label, using a fixed mapping to
>literal values.  (One way to do this would be to require that literals
>include typing information, perhaps looking something like INT(10) or
>STRING(10).)

That is not the intention, and I don't think it can be reasonably 
inferred from the text.

>
>While this may seem to be the only way to go, consider the case with XML
>Schema, where the interpretation of a ``literal'' depends on typing
>information that is specified elsewhere.  In XML Schema, you don't know
>what an element means unless you have acces to the schema.  I think that
>this translates to the following in RDF.  The interpretation of a literal
>in RDF+Schema depends on some typing information for the literal, which
>need not be specified with the literal.  I think that if RDF is to
>incorporate (aspects of) XML Schema it should be prepared to allow this
>sort of separate typing.
>
>Comments?

My understanding of the model theory is that it does allow this, 
though I agree that could be stated more clearly. The comment in 
section 1.2 (3rd paragraph) is intended to convey the idea that 
literals may turn out to be quite complex entities, perhaps partly 
defined by a schema, for example; NO assumptions are supposed to be 
made about the nature of literals, other than they are SOMEHOW 
syntactically distinguishable from URIs. That distinguishability may 
depend on any computational task performed by any lexicalizer or 
parser, however complex it may be. In particular, a 'literal' in the 
sense used by the model theory may be more complex than (and in any 
case different from) an xml:literal.

Hope this helps.

Pat



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Received on Thursday, 27 September 2001 23:49:03 UTC

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