Re: SKOS and Rules

Sean Bechhofer a écrit :

>>> The SKOS Core Guide includes reference to rules:
>>>
>>> http://www.w3.org/TR/swbp-skos-core-guide/#secaboutrules
>>>
>>> [[
>>> Inference rules are part of SKOS Core. Inference rules are
>>> described in prose, and where appropriate are expressed using the  Jena
>>> 2 rule syntax [Jena Inference], or as RDF statements using the OWL
>>> vocabulary [OWL]. Inference rules appear in boxes such as:
>>>
>>> An example rule.
>>>
>>> (?x ex:p ?y)
>>> ->
>>> (?x ex:q ?y)
>>>
>>> prefix ex: <http://www.example.com/eg#>
>>>
>>> ]]
>>>
>>> <snip>
>>> Is there going to be some notion of comformance? For example, does
>>> this mean that I *cannot* provide a SKOS implementation without  having
>>> some RDF repository that implements the rules -- and in that vein,
>>> what are the precise intended semantics of these rules?
>>
>>
>>
>> Alistair would perhaps be better placed than me to answer. However,  
>> I have worked with SKOS for quite a while now, and to me it is now  
>> quite natural to consider that the rules are part of the spec, and  
>> therefore should be implemented if one wants to implement a proper  
>> SKOS engine. This explain perhaps there have been cases of  
>> vocabularies represented using SKOS, but no "official" SKOS  
>> inference engine... (though such a thing wouldn't be too hard to  
>> implement, I suppose)
>> Concerning the semantics of the rules, well I suppose that the idea  
>> was just to have some production rule that would enable to specify  
>> formal inferences fitting what the SKOS model was trying to render.
>
>
> I'm not a hardline DLista, but with my vaguely formal hat on, I'd  
> certainly want to see this clarified. That would then make it easier  
> to see if such an engine really wasn't "too hard to implement...."

Agreed. Also concerning the critic on my lazy assumptions...

>
>> And I supposed that if OWL had offered means to represent general  
>> relational composition, there wouldn't have been such Jena-like  
>> axioms, but just OWL ones, as for e.g. the transitivity of  
>> skos:broader.
>
>
> I think the property chain inclusion axioms in the proposed OWL 1.1  
> [1] would cover the subject generality rule. Not sure about the  
> others though.

Well there are only 3 rules in [2] and I think only 2 (Subject 
Generality Rule and Ordered Collection Membership Rule) would be covered 
by the property chain inclusion axiom. I would be rather pessimistic 
regarding the third (in fact, first in document) rule, for collectable 
properties [3], because it deals with inferring a new fact which 
includes a property variable:
(?x ?p ?c) (?c skos:member ?m) (?p rdf:type skos:CollectableProperty)
->
(?x ?p ?m)

Cheers,

Antoine

[1] http://owl1_1.cs.manchester.ac.uk/overview.html

[2] http://www.w3.org/TR/swbp-skos-core-guide/

[3] 
http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20050510/#seccollectable

>
>> Whatever be the case, it is clear that this should be clarified for  
>> further version of SKOS. Notice by the way that some of the  
>> concerned axioms (either OWL ones or "rules") are quite  
>> controversial (well, I disagree with the relevance of some, and am  
>> not the only one), and might disappear from a further version of SKOS.
>
>
> Ok.
>
>     Sean

Received on Wednesday, 29 November 2006 09:15:54 UTC