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RE: OWL (or RDFS) and RDF and language tags

From: Michael Schneider <schneid@fzi.de>
Date: Wed, 6 Feb 2008 14:09:06 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A06C3038@judith.fzi.de>
To: "Lee Feigenbaum" <lee@thefigtrees.net>
Cc: <public-owl-dev@w3.org>
Hi, Lee!

Here is how I understand the situation.

AFAIK there is no way in OWL to have the specific set of plain literals as the range of some datatype property. The best you can do is to *not* specify a range at all, since this will at least /allow/ you to have plain literals (with or without a language tag) as values of such a datatype property. 

Technical background: The default range of a datatype property is rdfs:Literal (one can see this from [1]), which stands for the set of *all* possible data values, including the set of plain literals. But if you want to define a specific range, this range has to be one of the "built-in" datatypes of OWL, as listed in [2]. All these datatypes consist of non-plain literals, which do not allow the addition of a language tag (not even xsd:string). And the technical problem here is that all these datatypes are actually /disjoint/ with the set of plain literals. This means that you would get an inconsistent ontology, if you use a datatype property heaving a range defined with a plain literal.

Cheers,
Michael

[1] <http://www.w3.org/TR/owl-semantics/direct.html#3.1>
[2] <http://www.w3.org/TR/owl-semantics/syntax.html#owl_built_in_datatypes>

Lee Feigenbaum wrote:

>Hi everyone,
>
>It's been suggested to me that this would be a good place to ask the 
>following question. All suggestions or pointers are very much 
>appreciated!
>
>Is there either a standard way or a conventional way (best 
>practice) for 
>indicating that the range of a predicate is a localizable 
>literal (i.e. 
>plain literal with a language tag)? Similarly, is there a way to 
>indicate in RDF Schema or OWL that the range of a property should be a 
>plain literal w/ no language tag. (I guess that a datatype property of 
>with range xsd:string is semantically equivalent to a plain 
>literal with 
>no language tag, but that still doesn't address my first question).
>
>I read http://www.inter-locale.com/whitepaper/iswc2004.pdf but 
>couldn't 
>really make heads or tails as to whether it helps with my problem :) 
>(I've since also been pointed to 
>http://www.w3.org/2007/OWL/tracker/issues/71 which seems related to my 
>question, but I can't tell whether resolution of the issue would solve 
>my problem or not.)
>
>thanks,
>Lee
>
>

--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: Michael.Schneider@fzi.de
Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555

FZI Forschungszentrum Informatik an der Universität Karlsruhe
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Received on Wednesday, 6 February 2008 13:09:38 GMT

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