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Re: OWL Restrictions and RDF Named Graphs

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Fri, 23 Apr 2010 15:28:32 +0100
Message-Id: <7C837B2F-EF7A-4269-A150-DE491A40ADBD@cs.man.ac.uk>
Cc: Michael Schneider <schneid@fzi.de>, public-owl-dev@w3.org
To: nathan@webr3.org
On 22 Apr 2010, at 10:44, Nathan wrote:

> Michael Schneider wrote:
>> Hi Nathan!
>>
>> It is not clear to me what your actual question is and what you  
>> want to
>> achieve. But I can see several issues that I want to make you  
>> aware of. This
>> may help you to rephrase your question, or to reconsider your ideas.
>>
>> 1) Named graphs are not supported by OWL, neither semantically nor
>> syntactically.
>
> That's the problem I fear!

There are other problems ;)

>> two given statements
>>
>>   <http://ex.org/john#me> sioc:member_of <http://ex.org/groups#g1>
>>
>> and
>>
>>   <http://ex.org/groups#g1> sioc:has_member <http://ex.org/john#me>
>>
>> are equivalent, since the properties sioc:member_of and  
>> sioc:has_member are
>> equivalent. So you cannot use these statements as selection  
>> criteria, since
>> if one statement is asserted/inferred (by whatever means), the  
>> other will be
>> asserted/inferred as well.
>
> exactly, yet "john says he is a member of group-g1" is very  
> different to
> "group-g1 says that one of it's members is john". Belief states,  
> truth,
> unsure the precise term.

But that has nothing to do with the OWL statements. "John says he is  
a member of group-g1" and "john says that one of group-g1's members  
is john" (given that member and memberof are inverse) is exactly the  
same.

[snip]
> this would equate either:
>
> ASK {
>   GRAPH <group> {
>     <group> <has_member> <webid> .
>   }
> }
>
> or:
>
> ASK {
>   GRAPH <webid> {
>     <webid> <member_of> <graph> .
>   }
> }

Isn't all the work being done by the "GRAPH" clause?

> (or both)
>
> due to the delicate nature of access control, it is critically  
> important
> to be able to assert which graph(s) to check (or maybe trust?) at  
> runtime.
>
> In the above, perhaps if we swapped the term graph for resource it  
> would
> make more sense.. For some reason I feel that rdfs:isDefinedBy  
> could be
> leveraged in an owl:Restriction, but I could easily be (and often  
> am) wrong.


I think you are better off starting from some clear requirements or a  
scenario. At this point, I think you are reading things into the  
logic that aren't there. That usually goes with thinking you need  
things you in fact don't :)

Cheers,
Bijan.
Received on Friday, 23 April 2010 14:28:20 GMT

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