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Re: Ambiguity in description of DisjointClasses axiom

From: Ian Horrocks <ian.horrocks@cs.ox.ac.uk>
Date: Tue, 8 Nov 2011 13:30:28 +0000
Cc: public-owl-comments@w3.org
Message-Id: <2DA09993-3C17-4E21-B68C-C87DCEDCD20A@cs.ox.ac.uk>
To: Bill Duncan <wdduncan@gmail.com>
Bill,

I added this to the list of errata [1].

Thanks,
Ian

[1] http://www.w3.org/2007/OWL/wiki/Errata


On 7 Nov 2011, at 15:47, Bill Duncan wrote:

> To whom in may concern,
> 
> I think the description of the DisjointClasses axiom may need
> revising.  The informal description states:
> 
> 9.1.3 Disjoint Classes
> 
> A disjoint classes axiom DisjointClasses( CE1 ... CEn ) states that
> all of the class expressions CEi, 1 ≤ i ≤ n, are pairwise disjoint;
> that is, no individual can be at the same time an instance of both CEi
> and CEj for i ≠ j.
> 
> The "CEi, 1 ≤ i ≤ n" suggests that an axiom of the form
> "DisjointClasses( CE1)" is legal.
> 
> However, the formal grammar for DisjointClasses axioms is:
> 
> DisjointClasses := 'DisjointClasses' '(' axiomAnnotations
> ClassExpression ClassExpression { ClassExpression } ')'
> 
> And this clearly makes it clear that at least two ClassExpressions
> should be in a DisjointClasses axiom.  There is a bit of confusion,
> here, though.  Since axiomAnnotations are optional, one may also
> assume that the second ClassExpression axiom is optional (especially
> in the light of the "CEi, 1 ≤ i ≤ n" description above).
> 
> I suggest that you modify the informal description to read something like:
> 
> ....  DisjointClasses( CE1 CEi... CEn ) states that all of the class
> expressions CEi, 1 ≤ i ≤ n ...
> 
> I hope this suggestion is helpful,
> Bill
> 
> 
Received on Wednesday, 9 November 2011 08:30:21 GMT

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