Re: SKOS to RDFS/OWL ontology mapping

Bernard Vatant wrote:
> 
>>First, Alistair might define A skos:it B to mean:
>>   "B is the RDFS representation of the 'subject' that has A as SKOS
>>    representation".
> 
> 
> Sure it might. And keep agnostic about what this subject is. Although this declaration is
> not symetric.
> Is it made from eg: or foaf: namespaces' publishers viewpoint?

Alistair mentioned two properties, skos:it and skos:as that were the 
inverses of each other, so both communities could state such a fact in a 
simple manner.

>>Put another way, the existence of an
>>intermediate node does not preclude the use a direct property to
>>describe this relationship. Such a relationship can even be expressed in
>>OWL and so inferred automatically...
> 
> 
> Well, that sets another issue: What do we want this kind of assertion for? To make some
> kind of inference, and if so, which kind? My view was that what we want to capture here is
> at a level on which any inference would be risky.

I see that problem too. So let's try to think of a stupid example:

Imagine a web interface where books are marked as dc:subject ex:Dogs. It 
would be possible to add "See examples of dogs _here_", which would give 
us descriptions of instances of the class ex2:Dog. This is going from 
one paradigm to the other.

>>Second, you say "subjects have no identity". Unfortunately you
>>contradict this by giving the (admittedly blank) subject node the
>>(locally valid) identifier _:node1.
> 
> 
> I don't see any contradiction. The subject is not the node. The node is identified OK,
> although only locally, but not the subject itself which is only implicitely defined.
> Otherwise I won't use a blank node, I would define a resource, and assign an URI, and go a
> stage further in recursivity trap : what is the type of this resource, what are its
> properties etc. All the point is indeed to have the subject not identified to/by any
> resource, or any identifier of this resource. The node *is* not the subject.

Ok, I get your point... but what, then, is so extraordinary with the 
blank node? It's just a third "representation" of something, in your 
"Bernard subjects"-formalism :-) Or does the blank node have 
fundamentally different qualities compared to foaf:Person and ex:People?

> Hmm. Let's say I can claim this is something I have looked at quite closely for a certain
> number of years now - maybe to the point of blindness, though :)) See
> http://universimmedia.blogspot.com/

Oh, I hope you did not take offense... I did not mean to imply you did 
not understand. Obviously you're much more familiar with the issue than 
I am :-) I was just trying to get to the core of the issue you brought up...

>>I believe one good definition is "being separable from other things".
> 
> 
> I buy it. But separation in things is only possible in representations, because things
> exist only in representations. What I claim is that our "subject of conversation" is never
> identified as such, its'not an owl:Thing. We identify representations, and at some point
> we want to link two representations. Note that each representation taken standalone is
> built on specific logic rules. So logical integration of two different representation
> spaces is most of the time impossible if they are built on different logical frameworks.

Yes, agreed, the subject is never there. Are you also suggesting that 
the "subject" is just "framed" in different ways by representations, but 
never precisely identified?

So the questions remains: are RDFS/OWL and SKOS *really* different 
logical frameworks? Or rather, in what way are they different?

> 
>>If something does not have an identity, you cannot even use a blank node
>>to refer to it (because that shows it has an identity!).
> 
> 
> Nope. I have a Welfare number, an E-mail, a few Web Pages ... all of those identify some
> representation of me in a certain context. Every context has its own logic. You can grab
> an arbitrary number of those resources together in a node, that does not mean you captued
> my identity.

Hmmm, are "capture your identity" and "identify you" really the same 
thing? I would say the above things identify you, but not that they 
capture your identity... :-D

> You mean really ...
> 
> eg:People 	owl:sameAs	foaf:Person
> 
> ... in that case take your responsibility for all resulting semantic damage. I won't sort
> out the mess :)

:-)

> Show me a valid argument that they could be the same. For one they have not the same type.
> And certainly you can infer properties of the first that will seem very weird when applied
> to the other.

Could you give some examples? That would certainly help me.

/Mikael

-- 
Plus ça change, plus c'est la même chose