Re: Suggestion to change RDF encoding of HasKey axioms [RE: I've implemented the change to the syntax of HasKey]

If I put an RDF+RDF base semantics user's hat on, isn't it correct that 
the same property may be used both as an object and a data property? Ie, 
in many cases I would not really really care about this distinction. For 
such cases isn't it correct that the separation of the key properties 
would look fairly artificial?

Ivan

Michael Schneider wrote:
> Hi all!
> 
> After a private discussion with Boris yesterday evening, and after Boris' has now changed the Functional Syntax (FS) representation for Key axioms, I would like to suggest a corresponding change to the RDF representation. I am not particularly trying to press this change, since we currently have a working forward and reverse mapping between RDF and FS, and since we are very late in the day. However there are some drawbacks to be considered with the current situation.
> 
> 1) The RDF syntax for keys allows for arbitrary ordering of object and data properties. On the other hand, the changed FS representation of Keys now demands that all object properties precede all data properties. This has the effect that a round-trip from RDF to FS and back will shuffle the properties. Not everyone will like this.
> 
> 2) It would in general be nice if the RDF encoding and the FS encoding of a language feature are closely related. Currently, this is not the case.
> 
> 3) I believe the new forward mapping for Keys finally closes the door for having object/data property punning some day. The forward mapping asks for /any/ partition into object and data property sets. However, with property punning, there would be more than one possible partitions, and this would break the forward mapping.
> 
> 4) The semantic condition for Keys of the RDF-Based Semantics currently does not try to find out what the data properties in a Key axiom are, since this might not be possible in every case (it would need to be entailed somehow). This problem would immediately go away if one already knows positional information in the RDF encoding which of the properties are the data properties.
> 
> The following RDF encoding (modulo naming) would solve all these problems:
> 
>   _:x rdf:type owl:Key .
>   _:x owl:keyClass ex:C .
>   _:x owl:keyObjectProperties ( op1 ... opn ) .
>   _:x owl:keyDataProperties (dp1 ... dpn ) .
> 
> Now, both the forward and reverse mapping would be straightforward, and no property shuffling (not even within the lists) would be necessary anymore.
> 
> Disadvantages: 
> * Pretty verbose compared to the current encoding. 
> * Again new vocabulary terms. 
> * Yet another multi-triple RDF encoding.
>  
> Opinions?
> 
> Best,
> Michael
> 
>> -----Original Message-----
>> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org]
>> On Behalf Of Boris Motik
>> Sent: Friday, March 20, 2009 11:36 AM
>> To: 'W3C OWL Working Group'
>> Subject: I've implemented the change to the syntax of HasKey
>>
>> Hello,
>>
>> I've implemented the change to the syntax of HasKey; here are the diffs:
>>
>> Syntax:
>> http://www.w3.org/2007/OWL/wiki/index.php?title=Syntax&diff=20006&oldid=
>> 19848
>> (I've also updated one figure, so be sure to refresh your browser.)
>>
>> Direct Semantics:
>> http://www.w3.org/2007/OWL/wiki/index.php?title=Direct_Semantics&diff=20
>> 010&oldi
>> d=19792
>>
>> Profiles:
>> http://www.w3.org/2007/OWL/wiki/index.php?title=Profiles&diff=20007&oldi
>> d=20003
>>
>> XML Syntax:
>> http://www.w3.org/2007/OWL/wiki/index.php?title=OWL_XML_Schema&diff=2001
>> 1&oldid=
>> 19920
>>
>> RDF Mapping:
>> http://www.w3.org/2007/OWL/wiki/index.php?title=Mapping_to_RDF_Graphs&di
>> ff=20019
>> &oldid=19958
>>
>> Please let me know should you have further comments.
>>
>> Regards,
>>
>> 	Boris
>>
> 
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> Dipl.-Inform. Michael Schneider
> Research Scientist, Dept. Information Process Engineering (IPE)
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-- 

Ivan Herman, W3C Semantic Web Activity Lead
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