[SKOS] RE : Skos mapping issues

[Sorry I skept the subject in previous posting]

Hi Javier,
>
>
>
> Hi All,
>
> I am interested in the mapping of thesauri, so I have been reviewing the
> documentation available in the SKOS-Project. It seems that there is three main
> documents related with SKOS mapping in SKOS project [1,2,3].

Oops now I've realized that it was not so smart of me to release 3, because I have missed 2. And there are indeed some similarities between the two, which is normal since I intended to make an account of a SWD discussion in which Alistair played an important role. Some synchronization should be done, so your discussion is useful (and my main intent behind [3] was also to revive this discussion :-)

>
> Each one present a quite different approach to mapping representation. The last
> two documents it seems that try to simplify the skos mapping vocabulary.
>
> They map the partial and inexact equivalence relationships to other existent
> relations in SKOS core. The partial relationship is mapped to skos:broader and
> skos:narrower and the inexact is mapped or to skos:related or to a new
> skos:overlappingConcept.
>
> I agree that the semantic of the partial equivalence relationship is equivalent
> to the broader and narrower relationship. However, I think that the use of the
> same property would difficult the identification of the mappings respect to the
> basic ones. 

This is the crucial problem. The semantics are the same, so we should make them a same property.
Ideally the identification problem is distinct (in our working group we recorded it as [5]), so it should not intefere.
But of course in practice [5] is very difficult to solve in RDF, so in the end we might have to consider more than the semantics to define a property.

> I think that at least the namespaces should be changed (e.g:
> skosm.broader). This properties can be an specialization
> of the basic ones. This would facilitate the separation of the mappings to the
> core structure of each thesauri.

Problem is that specializing skos:broader might collide with the need to identify a skos:broader statement in a scheme in a way similar to the one you want to identify a mapping. Some people (cf [6]) would like skos:broader statements to hold only between concepts from one scheme.
I'm not a strong believer of this, but I certainly think that if we want to record mapping identification by creating a special property we should not make identification of intra-thesaurus links even more difficult than what it is now.

>
> I do not agree with the use of skos:related as inexact equivalence exposed in
> [2]. I think they are different. An inexact equivalence indicates
> that two concepts share some meaning and that not always happen with the more
> general skos:related relationship.
> A inexact equivalence relationship can be seen as an specialization of
> skos:related given that indicate a relationship
> between the concepts but not in the other way.

+1

>
> Respect to the compositions of mappings through "and", "or" and "not"
> relationships I think that to be able to create complex compositions as
> (A and B and (C or (D and E))), it would be needed a specialization of skos
> concept (called for example conceptCollection) to group all the composed
> concepts and the type of composition.
>
> I see that there are some similarities in the "and" relationship respect to the
> pre-coordination of labels in a thesaurus, and also
> respect to the composition in USE relationship to refer from a complex label to
> two simpler ones. However, I think they are
> some semantic differences between the "and" and the coordination making them not
> completely interchangeable.


This was the point in [3] to treat this "and" problem in the context of a different coordination problem which is on the SWD agenda [4]
Your point about "and" and pre-coordination is valid. There are case of complex mappings with conjunctions that could well correspond to post-coordination cases, and [4] is too narrow for this.
So we should re-introduce post-coordination in the loop by means of some specific "and". Something which semantics should be roughly
if x match (y andpostcoord z) then (if doc skos:subject x then doc skos:subject y and doc skos:subject z )

I think it is still a good idea to separate it from pre-coordination: in my current view (and I learned a lot reading the wise posts of this list, and could continue learning)
A mapping to a pre-coordination is a mapping to a single, even if complex, subject: the semantics would not imply infering new skos:subject triples. In this case the problem is delegated to [4]
A mapping to post-coordination would involve several subjects, as mentioned in the previous rule
Would such an approach alleviate your concerns?

Best,

Antoine

>
> [1] http://www.w3.org/2004/02/skos/mapping/spec/
> [2] http://isegserv.itd.rl.ac.uk/public/skos/press/dc2006/mapping.html
> [3] http://www.w3.org/2006/07/SWD/wiki/SkosDesign/ConceptualMapping/ProposalOne
[4] http://www.w3.org/2006/07/SWD/track/issues/40
[5] http://www.w3.org/2006/07/SWD/track/issues/47
[6] http://www.w3.org/2006/07/SWD/track/issues/36