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Re: [LC response] To Jonathan Rees

From: Jonathan Rees <jar@creativecommons.org>
Date: Mon, 30 Mar 2009 10:42:07 -0400
Cc: public-owl-comments@w3.org
Message-Id: <C2C587CA-7461-44F0-8F52-5003F69C8B69@creativecommons.org>
To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
On Mar 27, 2009, at 2:50 PM, Ian Horrocks wrote:

> Dear Jonathan
>
> We sent you a response [1] to your comment [2] on the OWL 2 Web  
> Ontology Language last call drafts, but to date we do not appear to  
> have received any reply. If we don't hear from you we will assume  
> that you are satisfied with the working group's response to your  
> comment.
>
> Regards,
> Ian Horrocks
> on behalf of the W3C OWL Working Group
>
> [1] http://lists.w3.org/Archives/Public/public-owl-comments/2009Mar/0044.html
> [2] http://www.w3.org/mid/760bcb2a0901251002p3e1be898s246b23e4284ac49a@mail.gmail.com

The definition of structural equivalence doesn't make sense. Here is  
what's in the wiki now:

<snip>
Instances o1 and o2 of the UML classes from the structural  
specification are structurally equivalent if the following conditions  
hold:

     * If o1 and o2 are atomic values, such as strings or integers,  
they are structurally equivalent if they are equal according to the  
notion of equality of the respective UML type.
     * If o1 and o2 are unordered associations without repetitions,  
they are structurally equivalent if each element of o1 is structurally  
equivalent to some element of o2 and vice versa.
     * If o1 and o2 are ordered associations with repetitions, they  
are structurally equivalent if they contain the same number of  
elements and each element of o1 is structurally equivalent to the  
element of o2 with the same index.
     * If o1 and o2 are instances of UML classes from the structural  
specification, they are structurally equivalent if
           o both o1 and o2 are instances of the same UML class, and
           o each association of o1 is structurally equivalent to the  
corresponding association of o2 and vice versa.
</snip>

By hypothesis, o1 and o2 are instances of UML classes. Therefore, by  
the first three points, atomic values, unordered associations, and  
ordered associations are all also instances of UML classes. As I do  
not know the details of UML I might assume that this is OK. However,  
the last bullet point repeats the hypothesis that o1 and o2 are  
instances of UML classes from the S.S. This does not sound right to  
me, and suggests a possible editorial improvement, if not an error.

I suggest rewriting to either remove the first hypothesis (at the very  
top) somehow, if atomic values and so on are not instances of UML  
classes, or the antecedent of the fourth bullet point, if they are.

Jonathan
Received on Monday, 30 March 2009 14:42:47 GMT

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