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Re: SKOS and OWL

From: NJ Rogers, Learning and Research Technology <Nikki.Rogers@bristol.ac.uk>
Date: Wed, 12 May 2004 14:12:46 +0100
To: "Miles, AJ (Alistair)" <A.J.Miles@rl.ac.uk>, "'public-esw-thes@w3.org'" <public-esw-thes@w3.org>
Message-ID: <125840000.1084367566@localhost.localdomain>

Yes I think this is really good text below.

I like the themes of
- skos = lower entry barrier
- skos = allows us to present a thesaurus view onto knowledge data

But I'd dare to go so far as to say that arguably the notion of owl-ish 
'things' and their subclasses doesn't apply so well to pretty abstract 
concepts such as 'fear' or, putting it another way, non-object-oriented 
things such as 'cycling'.
So for me the lower entry barrier isn't only thing - it's about offering 
the flexibility to be *either* casual or precise about how we believe some 
'things' to be subsumed by other 'things'. This in our attempts to organise 
and represent knowledge - particularly knowledge that covers abstract 

You may totally disagree!

BTW I agree with Dan re talking a bit about RDFS and OWL and subclassing 
versus KOS community notions of broader/narrower etc.


--On Friday, March 05, 2004 11:32:36 +0000 "Miles, AJ (Alistair) " 
<A.J.Miles@rl.ac.uk> wrote:

> Anticipating an FAQ item (and probably extended debate) on the
> relationship between SKOS and OWL, so I had a go at a draft on the
> subject.  I'd like to know what you think of this.
> Al.
> ----------------------------------------------------------
> Q: What's the difference between SKOS and OWL?
> A: OWL is the Web Ontology Language, now a recommendation from W3C.  OWL
> provides a powerful and expressive framework for adding well defined
> semantics (meaning) to data on the web.  Adding explicit meaning to data
> allows machines to communicate with each other, turning the web into an
> environment for effective machine to machine (M2M) interaction, as well as
> for human to machine (H2M) and human to human (H2H) interaction.  And
> because it is grounded in well-understood and formally defined systems of
> logic, we have the opportunity to reason over the data and discover new
> facts.
> But what happens when you give somebody (without a formal education in
> logic and set theory) an ontology editor, and ask them to create an
> ontology?  In my own experience, the results can be varied.  Most people
> grasp the basic notions of 'classes' 'individuals' and 'properties'
> without much trouble. However, one feature that I've seen misunderstood
> time and again is the 'sub-class' relationship, and the meaning of a
> class hierarchy.
> Organising things into hierarchies is a very natural thing to do.  It is
> akin to putting things into boxes, and the boxes into bigger boxes, so you
> have a measure of order to a number of things that is too large to hold in
> the mind at any one time.  Everybody who has a computer has a filesystem,
> divided into folders and subfolders.  But give a group of people the same
> set of files, and it's very likely that they'll create completely
> different directory structures for organising them.  The point I'm making
> is, hierarchies are natural, convenient and familiar, but different
> people can mean different things by a hierarchical relationship between
> two concepts.
> So often when you let someone loose on an ontology editor, they take one
> look at the class tree displayed on the left side of the window and treat
> it like a directory structure.  But the sub-class relationship has a very
> specific and formally defined meaning, which must be used appropriately if
> there is to be any guarantee of doing sensible reasoning and inference
> further down the line.
> So there is a definite niche for a tool that is simpler to wield than OWL,
> and won't break when confronted by the variations in peoples preference
> for different styles of knowledge organisation.
> That's where SKOS comes in.  SKOS stands for Simple Knowledge Organisation
> System.  It allows you to define some concepts, and organise them into
> basic and familiar structures, without having to be too strict about the
> implied semantics of those structures.  Of course SKOS is extensible, and
> any amount of semantic precision can be added (or borrowed from other
> schemas like OWL).  And of course SKOS is designed for maximal
> interoperability, so there are links between the SKOS property framework
> and the major vocabularies of RDF RDFS and OWL.  SKOS can be happily used
> alongside OWL, offering alternative views over the same underlying
> network of resources.
> The other major feature of SKOS is that it allows you to capture the link
> between a concept and the vocabulary (terminology) that is commonly used
> to refer to it.  So every concept is expected to have a 'preferred
> label', and may also be given any number of 'alternative labels'.  This
> feature can be used to turn any SKOS concept scheme or OWL ontology into
> a thesaurus. Capturing this information adds a lot of value, facilitating
> H2M and H2H interaction mediated by OWL ontologies or SKOS concept
> schemes.
> So SKOS does not try to compete with OWL in any way, but is in fact
> complementary to it.  It provides a simple and flexible framework for
> building knowledge organisation schemes.  This means a lower entry barrier
> for new users of the Semantic Web.  And it provides a path for bringing
> into the Semantic Web the large amounts of existing knowledge, captured in
> 'legacy' structures like thesauri, classification schemes, taxonomies and
> so on, that are not mapped easily into an OWL ontology.
> ---
> Alistair Miles
> Research Associate
> CCLRC - Rutherford Appleton Laboratory
> Building R1 Room 1.60
> Fermi Avenue
> Chilton
> Didcot
> Oxfordshire OX11 0QX
> United Kingdom
> Email:        a.j.miles@rl.ac.uk
> Tel: +44 (0)1235 445440

NJ Rogers, Technical Researcher
(Semantic Web Applications Developer)
Institute for Learning and Research Technology (ILRT)
Tel: +44(0)117 9287096 (Direct)
Tel: +44(0)117 9287193 (Office)
Received on Wednesday, 12 May 2004 09:05:45 UTC

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