SKOS without OWL

Antoine Isaac wrote:

> PS: Jakob and Bernard, when you talk about SKOS simplicity, don't
> forget that SKOS specification (and therefore proper use of SKOS)
> sometimes rely on OWL-like features like property transitivity
> ('characteristic' of  [1]) and even rules that are simple but out of
> OWL scope ('comment' in [2])
> 
> [1] http://www.w3.org/TR/2005/WD-swbp-skos-core-spec-20051102/#broader 
> [2] http://www.w3.org/TR/2005/WD-swbp-skos-core-spec-20051102/#subject

I still think you can have SKOS without OWL and inference (if you want).
OWL is only used to define logical characteristics of the properties as

* Transitive (owl:TransitiveProperty)
* Symmetric (owl:SymmetricProperty)
* InverseFunctional (owl:InverseFunctionalProperty)

Furthermore most properties have an inverse property (owl:inverseOf)


1. Transitivity

skos:broader and skos:narrower are defined as transitive. In my point of
view this is just an error of design in SKOS because if you inference
the transitivity rule, your full tree of concepts gets expanded. This is
not suitable for common retrieval tasks where you only want to expand to
a certain depth (please correct me if I am wrong). Your application
needs to expand skos:broader and skos:narrower depending on rules that
are independet from OWL anyway.


2. Symmetric and inverse properties

If you get data in SKOS you should *always* normalize it by checking and
adding inverse properties[*]. This could be done with SPARQL:

PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX owl:  <http://www.w3.org/2002/07/owl#>
CONSTRUCT    { ?x ?p1 ?y }
WHERE        { ?y ?p2 ?x. ?p1 owl:inverseOf ?p2 }

For this action you don't have to know anything about OWL. owl:inverseOf
is just a property that is identified by an URI.


Maybe OWL is needed for subjectIndicators because of
owl:InverseFunctionalProperty but normally you don't need the full
complexity of OWL to work with SKOS.

Greetings,
Jakob

[*] Because in practise (meta)data is always dirty and people with
always find ways to not use it in the way it was intended for.

Received on Monday, 13 November 2006 14:27:21 UTC