RE: Simple modelling of a temporal sequence

CORRECTION!

Existential restrictions are NOT disallowed to be placed on transitive
properties. Only cardinality restrictions are disallowed. 

I must have confused existential restrictions with min-1 cardinality
restrictions in my earlier mail. 

Sorry,
Michael

>-----Original Message-----
>From: Michael Schneider
>Sent: Tuesday, September 01, 2009 7:48 AM
>To: 'Matthew Graham'
>Cc: public-owl-dev@w3.org
>Subject: RE: Simple modelling of a temporal sequence
>
>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
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