ISSUE-130 Last Call Comment: skos:hasTopConcept and skos:topConceptOf

Dear Kjetil,

Many thanks for your comments and suggestions [1]. In respect of your
following comment:

"""
We have defined a 
sub:isMainConceptOf  a owl:ObjectProperty ; 
            rdfs:range skos:ConceptScheme ;
            rdfs:domain skos:Concept ;
            owl:inverseOf skos:hasTopConcept . 
so it was great to see that skos:topConceptOf is in! Please keep it there, it 
is simply much easier for us to use it in development with the present 
architecture.

I haven't followed the debate since this first was debated, but I would like 
to bring this up again: I do not like the naming of skos:hasTopConcept and 
skos:topConceptOf. As long as there are associative relationships in the 
system, it seems meaningless to make the hierarchical relationships more 
prominent than the associative by connecting this property to the hierarchy. 

So, that's why I called my inverse of skos:hasTopConcept isMainConceptOf. I 
think something like that would be better. 

I haven't thought too carefully about it, but what if:

<S> rdf:type skos:ConceptScheme ;
  skos:hasTopConcept <B> .

<B> rdf:type skos:Concept .

<A> rdf:type skos:Concept ;
        skos:related <B> .

would this be consistent?

I think that's fairly inevitable in our system, and it would certainly break 
things if we couldn't do this. What if <B> skos:broader <C> . ?
"""

As stated in the SKOS Primer [3], the skos:hasTopConcept provides an
efficient access to the entry points of broader/narrower concept
hierarchies. This property allows you to link a concept scheme to the
(possibly many) most general concepts it contains, as in the
(continued) animal thesaurus example:

ex:animalThesaurus rdf:type skos:ConceptScheme;
  skos:hasTopConcept ex:mammals;
  skos:hasTopConcept ex:fish.

A typical use of this property is to find and display the top levels
of a thesaurus in a tree browsing interface. Because this is such a
common requirement, we felt that it makes sense to have a property
such as skos:hasTopConcept which is designed to complement the
broader/narrower links in the scheme. If you require some other
mechanism for identifying entry points into a concept scheme which is
not dependent on broader/narrower links, we suggest you define a
custom property for this purpose. We propose to make no change to the
current specification, can you live with this?

On the subject of conventions and integrity conditions, the SKOS
Reference [2] states that the property skos:hasTopConcept is, by
convention, used to link a concept scheme to the SKOS concept(s) which
are topmost in the hierarchical relations for that scheme.

It was felt that a usage convention was sufficient to promote
interoperability in this case. Also there is no convenient way to
state an equivalent formal integrity condition using either RDFS or
OWL. Therefore, the graph below, whilst not strictly adhering
to the usage convention for skos:hasTopConcept, is nevertheless
formally consistent with the SKOS data model.

<MyScheme> skos:hasTopConcept <MyConcept> .
<MyConcept> skos:broader <AnotherConcept> .
<AnotherConcept> skos:inScheme <MyScheme> .

An application may reject such data but is not required to.  

There are neither usage conventions nor integrity conditions governing
the interaction between skos:hasTopConcept and skos:related. Therefore
the graph below is formally consistent with the SKOS data model.

<MyScheme> skos:hasTopConcept <MyConcept> .
<MyConcept> skos:related <AnotherConcept> .
<AnotherConcept> skos:inScheme <MyScheme> .

We are not aware of any use cases which suggest we define either usage
conventions or integrity conditions prohibiting such a graph.

Can you live with the specification as-is?

Kind regards,

Alistair Miles
Sean Bechhofer

[ISSUE-130] http://www.w3.org/2006/07/SWD/track/issues/130
[1] http://lists.w3.org/Archives/Public/public-swd-wg/2008Sep/0015.html
[2] http://www.w3.org/TR/2008/WD-skos-reference-20080829/
[3] http://www.w3.org/TR/2008/WD-skos-primer-20080829/

-- 
Alistair Miles
Senior Computing Officer
Image Bioinformatics Research Group
Department of Zoology
The Tinbergen Building
University of Oxford
South Parks Road
Oxford
OX1 3PS
United Kingdom
Web: http://purl.org/net/aliman
Email: alistair.miles@zoo.ox.ac.uk
Tel: +44 (0)1865 281993

Received on Thursday, 6 November 2008 18:07:50 UTC