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Re: ISSUE-26: SimpleExtension proposal

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Wed, 30 May 2007 15:28:16 +0200
Message-ID: <465D7BF0.2090800@few.vu.nl>
To: Daniel Rubin <rubin@med.stanford.edu>
CC: SWD WG <public-swd-wg@w3.org>

Hi Daniel,

[To others: just say if this starts getting boring and/or completely wrong]
>>>
>>> In the RadLex use case, for example, "terms" are entities in 
>>> reality, such as blood vessels. These are linked together via 
>>> relations such as "part-of" and "continuous-with".  It would be 
>>> better for these things to be called "Entity" instead of "Term".  I 
>>> think "Entity" would be consistent with terms and things in reality.
>> I think your "entity" proposal, I fear this is too ontology-oriented. 
>> SKOS exists to model knowledge organization schemes, as very specific 
>> intellectual constructs made of concepts (i.e. instances of 
>> skos:Concept), not entities in the world themselves. For this real 
>> world things, ontologies should be used, containing instances of 
>> owl:Class or rdfs:Class (notice that OWL features an owl:Thing that 
>> pretty much corresponds to the class of your "entities").
>
> I thought the goal of SKOS is to "provide a standard way to represent 
> knowledge organization systems." Ontologies certainly fall under that 
> umbrella. Some of the SKOS model is certainly very relevant to people 
> building ontologies.
Indeed. But assuming that a skos:Concept in a KOS actually denotes 
entities in the world in a formal way - i.e. making it a class - is an 
extra interpretation of your concepts.
For a clearer account on this things just have a look at 
http://www.w3.org/TR/swbp-skos-core-guide/#secmodellingrdf which tries 
to explain this distinction.

Notice however that if there is a modeling distinction, there is no 
exclusion. You can have skos:Concepts (my:Car rdf:type skos:Concept) 
that are also RDFS/OWL classes (ex:Car rdf:type rdfs:Class) so that you 
can create 'objects' which are classified under it (ex:danielsCar 
rdf:type ex:car). This would be needed by a range of applications 
(including RadLex) that require using SKOS features to define conceptual 
entities that are actually classes in ontologies.

Notice that such a trick is needed because SKOS does not make any 
assumption on the interpretations of instances of skos:Concept. Before 
you say it is an RDFS/OWL class (eventually just by creating an instance 
of it using rdf:type), your ex:Car is not expected to denote a set of 
"entities" in a "real" world (i.e. a concrete one, made of all kind of 
things like blood vessels and cars).
>
>
>
>> This is actually another point for not introducing "term" in SKOS, 
>> but something else, with much less "conceptual" load, like it was for 
>> "label". It would be too confusing, otherwise, with half  (or even 
>> more) of the existing thesauri assuming a "term-based" approach.
>
> I think I need to understand better exactly *what* SKOS is 
> describing--names of things? The things themselves? Both? Something 
> else?  To me, "term" is the name for something. "Concept" is something 
> that is someone's head. "Entity" is something that exists in reality. 
> There are certainly communities who need to describe things, names of 
> things, and both (in the case of RadLex). Ideally, SKOS should be able 
> to be useful to these communities.
I hope that my previous point helps. I think we are not that far way 
from each other anyway.

So to sum up my understanding, SKOS is meant to describe concepts, as 
"something in someone's head".
The point is that a concept can just stay in someone's head, or at  the 
level of a (set of) manifestation in one language. This is the level at 
which a skos:Concept would appear in a library, let's say. They know 
what a car is (skos:definition "a car is something that has four wheels, 
etc."), what it is semantically related to (skos:broader 
ex:TransportMeans) and what labels are used to name it in language 
(skos:prefLabel "car"@en). But their "world" do not contain any concrete 
car.
Then, if you have another world interested in car "entities" you would 
have to make your car an RDFS/OWL class, that denote set of concrete car 
entities (ex:danielsCar rdf:type ex:Car). But here we enter the field of 
ontology engineering, and we don't want SKOS to be redundant with RDFS/OWL
>
>
>> Do you see my point(s), Daniel? And do you think the "lexicalization" 
>> I've proposed in another mail to replace "term" (making it closer to 
>> the intuition behind "label") would make things less ambiguous?
>
> I don't recall what you want to replace "term" with.
"lexicalization". It's so natural that you have not spotted it in my 
sentence. Good sign ;-)

Cheers,

Antoine
Received on Wednesday, 30 May 2007 13:28:29 GMT

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