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Re: Ontologies for RDF structures, not just atoms

From: Pierre-Antoine Champin <swlists-040405@champin.net>
Date: Tue, 20 Apr 2010 08:48:25 +0100
Message-ID: <4BCD5C49.70103@champin.net>
To: Katasonov Artem <Artem.Katasonov@vtt.fi>
CC: "semantic-web@w3.org" <semantic-web@w3.org>

On 19/04/2010 13:41, Katasonov Artem wrote:
> (...)
> OWL is all about defining concepts corresponding to classes of
> resources: e.g. “Person”, “Woman”, “Husband”,  “Mother”, etc. But
> what about a concept like “Couple”? I bet you understand what I mean
> by this word, and this means that this concept is a part of an
> ontology we share. The meaning of “couple” is very simple: there is 
> John, there is Mary, and there is some ex:dates link between them.
> But OWL is useless for defining this concept - of course, unless we
> introduce a couple as a resource, define a couple of properties to
> link John and Mary to this resource, and add these all explicitly to
> the linked data space - which is, I believe, is unnatural and not
> feasible at a scale.

I find it neither unnatural or unscalable, really :)

If you need to consider the Couple as a concept, then you have to
'reify' it, litteraly 'make it a thing', i.e. a resource. Of course, you
would only do that *when* you need to consider the concept between a
relation (or more generally, a structure as you call it).

As a matter of fact, this is exactly what you do in english. If you only
need to state the fact that "John is dating Mary", you don't even need
the notion of a couple. That notion becomes necessary if you want to
state more things about their relation: "They have been a couple for two
years; they are a very happy couple.".

The good thing with english is that you can easily swap from the
'relation' view ("dates") to the 'reified' view ("couple"). In an
ontology, you have to *commit* (as in "ontological commitment") to a
particular representation, which really depends on the needs of your
application. You can also accept both representations, and add inference
rules that would state the equivalence between them :

  there is a ?couple involving ?john and ?mary
  ?john dates ?mary

but not all ontology languages would be able to express it (I don't
think OWL is).

Hope this helps. For more material about that, I recommend reading the
related section in Linked Data Patterns [1]. Funny to see the example is
almost the same :)


[1] http://patterns.dataincubator.org/book/qualified-relation.html

> In other words, I speak about an ontology of concepts that correspond
> to RDF fragments (structures, sub-graphs) rather than just RDF
> atoms.
> In past few years, I found myself designing and using some ad-hoc 
> frameworks for such ontologies in two different projects and,
> therefore, contexts. One was about interpretation of RDF-encoded
> mental structures (beliefs, intentions) and communications (speech
> acts) in multi-agent systems. The other, current, is about
> interpretation of RDF-encoded software models. In both cases, the
> problem in nutshell is the following: there is an RDF graph for
> something and we want to detect if a certain “situation” occurs in it
> – to make some conclusions based on that. It is like answering a
> question about if there are any couples in a group of people. As
> “situation” of interest are many, we want to have a formal ontology
> of those. In other words, I believe that the applications where the
> problem occurs can be rather widespread.
> I plan to work on this further, maybe to generalize on the approaches
> I used before.
> I wanted to ask for any tips about related previous research, 
> discussions, postponed issues in standard-setting groups. Anyone is
> familiar with anything like this? Please comment also on the problem
> as such. Thanks in advance
> Artem Katasonov VTT Techncal Research Center, Finland
Received on Tuesday, 20 April 2010 07:49:04 UTC

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