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RE: firts and rdf:rest as functional property

From: Michael Schneider <schneid@fzi.de>
Date: Fri, 20 Mar 2009 17:59:46 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A0011D9B09@judith.fzi.de>
To: Reto Bachmann-Gmür <reto.bachmann@trialox.org>
Cc: "Semantic Web" <semantic-web@w3.org>, "Bijan Parsia" <bparsia@cs.man.ac.uk>
>-----Original Message-----
>From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org]
>On Behalf Of Reto Bachmann-Gmür

>The example 2 violates what's the convention described by RDF semantics,
>however I see no way to add tbox statements with the (current)
>expressivitiy of OWL that would contradict this graph.

Me neither.

[...]

>> (2) Lists should not be cyclic, though this is possible with RDF lists:
>>
>>       A -> B
>>       ^    |
>>       |    v
>>       D <- C

Try to express such a general cycle prohibition axiom! This would roughly
need to say something like:

  For any non-negative integer n:
    there must not be nodes x1,...,xn
    such that
       x1 rdf:rest x2
       x2 rdf:rest x3
       ...
       xn rdf:rest x1

If the cycle size would be restricted, one could express this by a finite
set of axioms (I'm not necessarily talking about OWL here). But the cycles
may be arbitrarily large, so this is not possible.

Michael

--
Dipl.-Inform. Michael Schneider
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Received on Friday, 20 March 2009 17:00:27 GMT

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