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Re: Skolemization Proposal in RDF 1.1 working draft

From: Michael Schneider <schneid@fzi.de>
Date: Sun, 15 Jul 2012 00:34:47 +0200
Message-ID: <5001F407.10903@fzi.de>
To: Alan Ruttenberg <alanruttenberg@gmail.com>
CC: Pat Hayes <phayes@ihmc.us>, David Booth <david@dbooth.org>, "semantic-web@w3.org" <semantic-web@w3.org>, OWL Working Group <public-owl-wg@w3.org>
Hi Alan!

Am 14.07.2012 23:45, schrieb Alan Ruttenberg:

> Rather it appears that this gives sanction to *rewriting* graphs
> to be different graphs (spec saya "tranformed") and my concern is that
> this rewriting process will destroy OWL serializations.

Yes, if blank nodes are replaced by URIs, then this will destroy many 
OWL DL ontologies (in RDF graph form). All class expressions, complex 
data ranges, a few axioms (n-ary disjointness axioms and negative 
property assertions), and certain forms of annotations are written with 
a blank node that "glues together" the different triples that encode the 
language construct. In a few cases (intersection, union and 
enumeration), it is, for backward compatibility reasons, also allowed to 
use a URI, but in all other cases (e.g. for property restriction 
expressions), it is not. Further, the argument lists of all 
multi-argument language constructs, such as class intersection or n-ary 
disjointness axioms, are constructed from several blank nodes. So there 
are a lot of options for an OWL DL ontology to be hurt by a replacement 
of blank nodes by URIs.

Probably, it wouldn't be a big thing for OWL DL tools to internally 
"repair" such ontologies, that is, to allow for URIs where blank nodes 
would be expected, but such ontologies would still count as formally 
invalid OWL DL ontologies.

Cheers,
Michael

-- 
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Dipl.-Inform. Michael Schneider
Research Scientist, IPE / WIM

FZI Forschungszentrum Informatik
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Fax: +49 721 9654-727

michael.schneider@fzi.de
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Forschungszentrum Informatik (FZI) an der Universität Karlsruhe
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Received on Saturday, 14 July 2012 22:35:12 GMT

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