Re: Ontologies for RDF structures, not just atoms

Hi Simon,

On 21/04/2010 19:49, Simon Reinhardt wrote:
> Hi Pierre-Antoine,
> 
> Yes, you are completely right, my bad.
> 
> Property chains have their limitations in cardinality constraints and
> they also can't be used to reify datatype properties but I still
> think that for most cases they are useful enough and provide a simple
> means to declare shortcuts.

Agreed.

> Think about it: in your data you will only need to use the "reified
> property classes" if you want to attach additional information to a
> relationship and then the simple relationship gets inferred.
> Otherwise you state the simple relationship. Now when you query the
> data you can do the same: if you're interested in additional data
> about some relationship then you will use the "reified property
> class" in your query pattern - which might not match if the data only
> uses the simple relationship but that's no problem because in that
> case the data will not contain any additional information about the
> relationship anyway. And if you're just interested in the existance
> of the relationship then you can use the simple relationship in your
> query pattern because that will always be there, either explicitly
> stated or inferred. What would be a use-case where you need to infer
> the reified version?

Imagine that ontology-1 defines a class 'Couple', while ontology-2
defines a relation 'dates'. I would like to be able to mix datasets
using both ontologies, and query them using the ontology of my choice.

In that case, OWL is not adapred -- and that is ok with me, one size
does not fit all, and OWL is not suited for everything, nor should it
be. I think Holger's remark was about that: know your tools and their
limitation, and chose the right tool for a given problem.

  pa


> @Holger: And btw, I don't think that's bending OWL to any particular
> needs - this is exactly what property chains have been added to the
> language for. It's all just different perspectives on the same thing,
> whether you think of it as reification or as providing shortcuts - in
> the end it's just a modelling pattern.
> 
> Regards, Simon
> 
> 
> Pierre-Antoine Champin wrote:
>> Hi Simon,
>> 
>> with OWL property chains, you can express the 'ONLY IF' part of the
>> rule below, but not the 'IF' part, because a single property be a
>> subprop of a property chain, but not the other way around.
>> 
>> pa
>> 
>> On 20/04/2010 20:38, Simon Reinhardt wrote:
>>> Pierre-Antoine Champin wrote:
>>>> The good thing with english is that you can easily swap from
>>>> the 'relation' view ("dates") to the 'reified' view ("couple").
>>>> In an ontology, you have to *commit* (as in "ontological
>>>> commitment") to a particular representation, which really
>>>> depends on the needs of your application. You can also accept
>>>> both representations, and add inference rules that would state
>>>> the equivalence between them :
>>>> 
>>>> there is a ?couple involving ?john and ?mary IF AND ONLY IF 
>>>> ?john dates ?mary
>>>> 
>>>> but not all ontology languages would be able to express it (I
>>>> don't think OWL is).
>>> 
>>> In OWL 2 you can do that using property chains.
>>> 
>>> Suppose you have a class ex:Couple representing your reified
>>> couple concept and a relation ex:coupleMember linking an
>>> ex:Couple to a foaf:Person (with the cardinality restricted to
>>> two if you want, although that might be problematic in
>>> combination with property chains, I'm not sure). Then you can
>>> declare that for the path going from a foaf:Person to an
>>> ex:Couple (using the inverse of ex:coupleMember) and then going
>>> from that ex:Couple to another foaf:Person (this time using
>>> ex:coupleMember itself) there exists a shortcut, namely
>>> ex:dates.
>>> 
>>> In Turtle syntax:
>>> 
>>> ex:dates a owl:ObjectProperty ; owl:propertyChainAxiom ([a
>>> owl:ObjectProperty ; owl:inverseOf ex:coupleMember]
>>> ex:coupleMember) .
>>> 
>>> 
>>> Regards, Simon
>> 
>> 
>> 
>

Received on Thursday, 22 April 2010 07:32:57 UTC