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RE: Simple modelling of a temporal sequence

From: Michael Schneider <schneid@fzi.de>
Date: Tue, 1 Sep 2009 07:47:42 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A00165E779@judith.fzi.de>
To: "Matthew Graham" <mjg@cacr.caltech.edu>
Cc: <public-owl-dev@w3.org>
Hi Matthew!

It sounds to me that you want to put an existential restriction on a 
transitive property ("after"). Since you refer to OWL DL below, let 
me say that doing so is not allowed in OWL DL, i.e. your ontology
is not a syntactic valid OWL DL ontology. See

<http://www.w3.org/TR/owl-semantics/syntax.html#transitivity_side>

So you should not expect any OWL DL reasoner to do any reasoning
at all on your ontology, but rather expect it to signal a syntax 
error.

Now, you did not tell us which reasoner you are using. For example, 
if you are using Pellet, then note that this reasoner actually
performs reasoning in this situation, but only after first dropping 
the transitivity axiom from "after". See

<http://clarkparsia.com/pellet/faq/owl-full/>

"""
OWL-DL Restriction: OWL DL requires that no cardinality constraints 
(local nor global) can be placed on transitive properties or their 
inverses or any of their superproperties.

Pellet Restriction: Pellet requires this restriction. Any 
transitivity axiom violating these restrictions are ignored 
(cardinality restrictions are not ignored).
"""

Cheers,
Michael

Matthew Graham wrote:

>Hi,
>
>I'm trying to model a simple temporal sequence with a class called
>Stage which has 5 subclasses: 2-cell, 4-cell, 8-cell, 16-cell and 32-
>cell.
>
>There are also four object properties: startStage, endStage, before
>and after. before and after are defined to be transitive and inverse
>to each other and with domain Stage and range Stage.
>
>32-cell is then defined to be: after some 16-cell; 16-cell is defined
>as: after 8-cell; etc.
>
>Finally I declare an individual called ptype1 with startStage some 4-
>cell.
>
>I then run the reasoner on the ontology and try the DL Query:
>startStage some (before 8-cell)
>
>This does not return ptype1. Why not? Do I have to explicitly state
>the inverse relationships, e.g. 16-cell before some 32-cell, as well -
>why are these not inferred during reasoning?
>
>	Cheers,
>
>	Matthew

--
Dipl.-Inform. Michael Schneider
Research Scientist, Dept. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: michael.schneider@fzi.de
WWW  : http://www.fzi.de/michael.schneider
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Received on Tuesday, 1 September 2009 05:48:25 GMT

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