RE: Last Call: SKOS Simple Knowledge Organization System Reference; SKOS Primer updated -- SKOS comment

Congratulations on a fine piece of work!


Some relatively minor comments


--- On the SPEC


1. SKOS Collections

While SKOS collections represents best practice in thesaurus construction, many prominent existing thesauri (and related KOS) do not follow the SKOS collections semantics. Instead, they model guide terms, facet indicators etc as part of a hierarchy using standard Broader/Narrower relationships. This creates a problem in converting such existing KOS into SKOS. From discussions it appears other people have come to a similar judgment in converting such cases to SKOS - being reluctant to change the existing structure of a KOS designed by a third party. The pragmatic decision is often to create a (nonSKOS) property of a concept, to say essentially, 'NOT_FOR_INDEXING'. This allows a basic distinction to be made between a facet indicator (or guide term) and a concept available for indexing.


Can we consider if something like this could be introduced into SKOS to facilitate conversion of many legacy KOS? The primer can always encourage the full collections approach as best practice.




I think the treatment of SKOS Broader and broaderTransitive is a good flexible solution.



--- Comments on the documentation:-



2.  In section 1.3, as well as the cost/benefit argument for SKOS (in KOS versus a formal ontology), I think it is also possible to make an argument based on intended purpose. Some KOS (by design) do not represent a 'logical' view of their domain and are only converted to a formal logic representation in practical terms by changing their intended purpose.



Does the Reference deal with SKOS specialisation (I see the Primer does)?



3.  possible typo in 2.3.1 Note-not transitive vs. intransitive: 

I'm not sure this says what is intended? There seem to be too many double negatives in sentence quoted below 

 "Not specifying skos:broader as transitive implies that no new skos:broader statement cannot be inferred between cats and animals by applying SKOS semantics. "


4. Open world discussion and extension vs mapping in 3.1 and 3.2

I'm a little concerned about the relative emphasis apparently given to extension vs mapping. The primer might be read as suggesting that the default way of connecting two KOS is via extension or direct linking, which I think would be inappropriate. While there are good cases for (third party) extending a KOS (eg by including local extensions), the wording in the intro to section 3 is perhaps a little enthusiastic and might run the risk of not sufficiently recognizing the potential problems of linking two different KOS. LIS experience has recognised that any major KOS represents a particular world view and that joining two different KOS in an effective manner is not necessarily straight forward. Hence the emphasis on distinct mapping relationships.


Perhaps the editorial team could consider the appropriate order of the linking and mapping sections, whether more discussion on the rationale for mapping could be included, and whether some more guidance might be given on when to link and when to map.


The linking example in section 3.1 brings up a currently somewhat problematic issue.


A new concept scheme can re-use existing concepts using the skos:inScheme <>  property. Consider the example below, where a reference concept scheme for animals defines a concept for "cats":


However there is nothing to prevent a new developer attaching their own new concept to someone else's existing SKOS scheme and thus changing the scheme (if the links are followed). It would be bad practice but as far as I understand is possible. (A slight modification of the example in 3.1 illustrates the point below.) 


I appreciate this is integral to the open world model and in the long run, it might be addressed by mechanisms of assigning provenance to RDF (sets of) statements, development of trusted vocabulary registries, caution when importing a SKOS vocabulary, etc. In the near future, I believe that the majority of applications will be effectively closed world, in that they will create an in-house index or database based on selected resources from the Web (including linked data publications). Perhaps the SKOS primer might also address more immediate concerns of how a vocabulary provider might make their vocabulary available. Is it possible to say something on how KOS developers might publish a vocabulary in SKOS, while asserting some practical form of ownership?



Eg A slight modification of the example in 3.1 if I understand it correctly
============= alt example (undesirable?)
ex1:referenceAnimalScheme rdf:type skos:ConceptScheme;
   dc:title "Reference list of animals"@en <mailto:> . 
ex1:cats rdf:type skos:Concept;
   skos:prefLabel "cats"@en <mailto:> ;
   skos:inScheme ex1:referenceAnimalScheme.

The creator of another concept scheme devoted to cat descriptions can freely 
include the reference ex2:abyssinian concept in AN EXISTING scheme, and then reference it as follows:

ex2:catScheme rdf:type skos:ConceptScheme;
   dc:title "The Complete Cat Thesaurus"@en <mailto:> . 

ex1:cats skos:inScheme ex2:catScheme.

ex2:abyssinian rdf:type skos:Concept;
   skos:prefLabel "Abyssinian Cats"@en <mailto:> ;
   skos:broader ex1:cats;
   skos:inScheme ex1:referenceAnimalScheme.






Douglas Tudhope

Professor, Faculty of Advanced Technology

University of Glamorgan

Pontypridd CF37 1DL

Wales, UK

Tel +44 (0) 1443-483609

Fax +44 (0) 1443-482715

Editor : The New Review of Hypermedia and Multimedia




From: on behalf of Alistair Miles
Sent: Thu 04/09/2008 16:35
Subject: Last Call: SKOS Simple Knowledge Organization System Reference; SKOS Primer updated

The W3C Semantic Web Deployment Working Group is pleased to announce the
publication of a Last Call Working Draft for the Simple Knowledge
Organisation System Reference (SKOS):

Our Working Group has made its best effort to address all comments received
to date, and we seek confirmation that the comments have been addressed to
the satisfaction of the community, allowing us to move forward to W3C
Candidate Recommendation following the Last Call process.

The Working Group solicits review and feedback on this draft specification.
In particular, the Working Group would be keen to hear comments regarding
any features identified at risk, and from those implementing (among others):

* Editors:  editors that either consume or produce SKOS;

* Services: vocabulary services that provide access to vocabularies using

* Checkers: applications that check whether the constraints on SKOS
vocabularies have been violated.

Comments are requested by 3 October 2008, at which time the Working Group
intends to close Last Call. All comments are welcome and should be sent to; please include the text "SKOS comment" in the subject
line. All messages received at this address are viewable in a public

The Working Group intends to advance the SKOS Reference to W3C
Recommendation after further review and comment. This Last Call Working
Draft signals the Working Group's belief that it has met its design
objectives for SKOS and has resolved all open issues.

The Working Group has also published an update of the companion SKOS Primer:

The Working Group expects to revise this Primer while the SKOS Reference is
undergoing review and eventually publish the Primer as a Working Group Note.

Please see also:

Kind regards,

Alistair Miles
Sean Bechhofer

Alistair Miles
Senior Computing Officer
Image Bioinformatics Research Group
Department of Zoology
The Tinbergen Building
University of Oxford
South Parks Road
United Kingdom
Tel: +44 (0)1865 281993

Sean Bechhofer
School of Computer Science
University of Manchester

Received on Friday, 3 October 2008 18:12:28 UTC