RE: Broader, collections and the difference between SKOS and OWL

Jane Greenberg asked:
> Is not SKOS grounded, at least to some degree, in thesauri standards, 
> such as Z39.19, ISO 5964, ISO 2788..and general controlled vocabulary 
> practices of for named entity systems? (Doris Clack is a genius 
> here.)
> 
> If not, why not?  My understanding is that these standards 
> have played a 
> role in the development of SKOS.

Yes, SKOS was guided by these standards and particularly BS 8723-2,
which all relate to thesauri. However, it also has ambitions to enable
data exchange with other types of vocabulary, such as taxonomies,
classification schemes, subject heading schemes and even folksonomies.
These different vocabulary types have different approaches to
hierarchical linkages. It is hard to satisfy all of them at once. In
other words, you have to drop some of the constraints on strict
hierarchical relationships - just accepting that whatever the vocabulary
editor set up should be accepted without question. 

The tension between imposing strict semantic constraints and trying to
serve everybody comes up again and again in the discussion list. For
example, here's part of an exchange between myself and Antoine Isaac a
few weeks ago, on ISSUE 44 (BroaderNarrowerSemantics):

Stella:
> But what is SKOS really for? If its aim is to provide a single format 
> that can be used to transmit and receive any type of vocabulary, then 
> we should adopt Bernard's suggestion. But if the purpose is to enable 
> simultaneous searches across collections that have been indexed or 
> classified with a variety of different types of vocabulary, then a 
> more complex semantic structure may be needed. Allowance needs to be 
> made for the different ways of handling notations, preferred terms and

> captions, as well as the hierarchical relationships. I suppose the 
> allowance could be made by the search engine rather than in SKOS 
> itself, but how would that work?
>
> Maybe I've never been sure of what SKOS is for. The SKOS Core Guide
> says:
> "SKOS Core provides a model for expressing the basic structure and 
> content of concept schemes (thesauri, classification schemes, subject 
> heading lists, taxonomies, terminologies, glossaries and other types 
> of controlled vocabulary)" These vocabulary types have several 
> intrinsic fundamental differences, and the differences are not about 
> to go away. If SKOS seriously wants to model the semantics/structure 
> of all of these in one scheme, it may have to get quite a bit more 
> complex than it is!
>   
Antoine:
"To me SKOS is really intended to be the common denominator for a number

of approaches to create KOSs, mainly for the KOSs intended as 
(conceptual) languages for description and retrieval: thesauri, etc. As
such, there are two options envisioned, as you recall it:
- keep basic, and present a model that allow to represent the 
fundamental features recurring in these approaches, even if to represent

them on a quite superficial level (with limited semantic definitions);
- be extensive: offer modelling features as well as semantic constraints

that fit each of these different approaches (which might be a bit what 
Ceri hinted at in [2])

"I would follow the first option, and would like to emphasize (and 
propose to discussion) the two following reasons for it:
1. SKOS is for the semantic web, and it should therefore present simple,

and, importantly, pragmatic approach for KOS representation. Perhaps 
some people around here will find it debatable, but I think SKOS should 
for instance accomodate the representation of Wikipedia categories [3] 
in SKOS, without having to spend years on re-structuring the complete 
thing.
2. SKOS shall not enter in a competition with all kind of initiatives 
that are currently running, and whose aim is to carefully define and 
give guidelines for the design of precise KOS categories, e.g. BS 8723. 
SKOS has to be compatible with the models these initiative build, this 
does not mean that it has to represent all what the corresponding models

are up to.

"Indeed that implies the opposite: if we want to be compatible with
these 
different approaches (that is, if e.g. BS 8723 want to define its 
thesaurus model as an extension/refinement of SKOS, which is how it 
should be done, I believe) we have to be very careful with the semantic 
conditions we introduce.
It might be frustrating (and most of the time it is for me), because it 
results in an ontology that is more lightweight than what was thought of

initially. But I think we cannot really avoid that, that's an inherent 
part of this "let's design a semantic web standard" game.

Best,

Antoine"

Well, I'm usually just a lurker on this list. But it's intriguing to see
how this conundrum keeps recurring. Hopefully time will show how well
the evolving solutions cope with real use cases. BTW, you can see the
basic model for BS8723 in UML at http://schemas.bs8723.org/, latest
version at http://schemas.bs8723.org/2008-01-08/Documentation/Home.html

Enjoy it,
Stella
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Stella Dextre Clarke
Information Consultant
Luke House, West Hendred, Wantage, Oxon, OX12 8RR, UK
Tel: 01235-833-298
Fax: 01235-863-298
stella@lukehouse.org
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Received on Tuesday, 19 February 2008 17:28:15 UTC