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Re: loop free?

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Tue, 30 Sep 2003 21:46:42 +0100
Message-ID: <3F79EBB2.6050303@hplb.hpl.hp.com>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-webont-wg@w3.org


A loop is a technical term in graph theory for a cycle of length of one.

I personally find that the current text prohibits that with the words 
"pair" and "undirected graph"  (most authors permit loops in directed 
graphs and prohibit them in undirected graphs).

If we have a test case that includes a loop and is hence not in DL then 
that will be adequately clear, and we can avoid textual change to S&AS.

 From the design point of view since the disjointWith does not allow loops, 
it seems slightly cleaner to prohibit them for equivalentClass - it's 
easier to code though without such a constraint.

Jeremy


Peter F. Patel-Schneider wrote:

> I don't particularly care one way of the other here, but I don't see any
> need to forbid loops (of any sort).  As well, the wording that you propose
> could be read as forbidding non-trivial loops.
> 
> peter
> 
> 
> 
> From: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
> Subject: loop free?
> Date: Tue, 30 Sep 2003 15:19:57 +0200
> 
> 
>>Concerning
>>http://www.w3.org/TR/2003/CR-owl-semantics-20030818/
>>
>>
>>Peter,
>>
>>an editorial suggestion on the mapping rules:
>>
>>[[
>>T(descriptioni) owl:equivalentClass T(descriptionj) .
>>for all <i,j> in G where G is a set of pairs over {1,...,n}x{1,...,n}
>>that if interpreted as an undirected graph forms a connected graph for
>>{1,...,n}
>>]]
>>
>>suggest
>>
>>s/a connected graph/a loop-free connected graph/
>>
>>I think the case <i, i> in G is already excluded by the word "pairs" but it
>>is arguable. For most readers undirected graphs are loop free by definition;
>>but since we do not provide one ...
>>
>>
>>
>>
>>
>>(I should add a test case for
>>
>>_:b owl:equivalentClass _:b .
>>_:b rdf:type owl:Class .
>>_:b owl:unionOf rdf:nil .
>>
>>as being in OWL Full, similarly
>>
>>_:b owl:disjointWith _:b .
>>_:b rdf:type owl:Class .
>>_:b owl:unionOf rdf:nil .
>>)
>>
>>My code, which now passes all the tests except I5.8-016, would fail those
>>two I think :(
>>
>>Jeremy
>>
>>
>>
Received on Tuesday, 30 September 2003 16:47:29 GMT

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