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Re: The notion of a "classification criterion" as a class

From: Bene Rodriguez-Castro <beroca@gmail.com>
Date: Fri, 30 Apr 2010 13:22:06 +0100
Message-ID: <i2qea8cd28f1004300522k421fd205sbe31bee69629535f@mail.gmail.com>
To: "[ontolog-forum]" <ontolog-forum@ontolog.cim3.net>, public-owl-dev <public-owl-dev@w3.org>
Cc: phayes@ihmc.us, rector@cs.man.ac.uk, sowa@bestweb.net
On Sun, Apr 25, 2010 at 8:56 AM, Pat Hayes <phayes@ihmc.us> wrote:
>
> But why would it be hard to accept? After all, the semantic model
> underlying OWL-DL is very straightforward. So, ask how your vision can
> be re-stated in terms of classes considered as simple sets. What
> differences **between sets** could account for the distinction between
> Wines and WinesByColor ? And I think it is fairly clear that there is
> no difference between them, when they are considered as sets,
> independent of the class hierarchy you see them as belonging in. They
> have to be the same set: so, in OWL-DL, they have to be the same class.
>
> I suspect that you are used to thinking of classes as nodes in a
> classification hierarchy, but that is not the primary OWL intuition.
> The subclass hierarchy in OWL-DL is simply a consequence of the
> extensional subset relationship: if all the members of A are also
> members of B, then A is a subClass of B. That is what subClass
> **means** in OWL-DL (and similar languages.)
>
> I find it interesting that you feel that the normalized ontology seems
> to 'need' these XByY classes, and that the **structure** 'seems to be
> asking' for them (my emphasis.) But this way of thinking is entirely
> alien to the semantics of OWL (or any other extensional - set-based -
> language), where the 'structure' of the subsumption hierarchy is
> emergent rather than imposed from above. Subsumption here is a binary
> relation between sets, and is determined entirely by their membership.
> Any "structure" that the overall hierarchy has must arise from this
> purely binary relationship.
>
> Good luck with your project, but you need to be using a formalism with
> a different kind of underlying semantics than that used by OWL-DL.
>
> Pat Hayes
>

Hi Pat,

I can see now that under OWL semantics it is not useful to introduce
these XbyY classes in the inheritance structure of the ontology.
However, I might still have to find a sensible mechanism to represent
in OWL DL the type of information that these classes provide.  I'll
try to summarize the main reasons for this in my research because it
is very possible that some of the assumptions along the way are
debatable.

* The aim is to put forward an ontology design pattern (or patterns)
within OWL DL to model a particular type of domain concept.  A domain
concept prone to be represented by multiple alternative classification
criteria (similar to the examples of :Person, :Wine or to an
additional example cited below, "dish detergent").

* After a survey of ontology design methodologies, there seems to be a
lack of guidelines on how to *identify* the classification criteria of
such concepts and how these concepts can be represented *together with
their classification criteria* in an ontology model.

* To *identify* the relevant classification criteria to be considered,
I am trying to propose an adaptation of part of Spiteri's simplified
model for *facet analysis*[1][5].  As a neat example, notice the
conceptualization of the "dish detergent" concept developed using
Spiteri's method in this technical report[2].  I think the final
conceptualization obtained in the form of a "faceted classification
scheme", could be a suitable starting point for the representation of
(in this case) the "dish detergent" domain concept in an ontology
model where (in most cases), a facet would correspond to a
classification criterion.  (Incidentally, some comments in this
ontolog-forum thread[3][4][5] speaks favorably of the use of faceted
classification systems as a point of reference for ontology design).

* To provide a "valid" fit-for-purpose OWL DL representation of this
particular type of domain concept, I intend to use the cited
Normalisation mechanism which seems a very suitable and effective
approach to achieve it.  The mechanism refers to different "semantic
axes" of the domain concept being normalised where (in most cases) a
semantic axis would correspond to a classification criterion.
(Nonetheless, as per John's recommendation, I will look into FCA
methods as well).

* But in addition, I would propose to "augment" the normalised
ontology model to include information about how many classification
criteria of the domain concept in question are represented in the
model and which classes (or properties) are associated to each
classification criterion.  This is the idea that motivated the "need"
of the hypothetical XbyY classes.

* After comments in this thread, I believe the information provided by
the XbyY classes could be considered "meta-knowledge" (knowledge about
elements of the ontology, in this case other classes).  The potential
representation of this meta-knowledge about classification criteria,
could effectively provide a "mapping" between the ontology and the
faceted classification scheme that the ontology was based on.
"Faceted-friendly" applications aware of this mapping, could exploit
it for example, enabling new ways of visualizing, navigating or using
the data that will populate the ontology over time.

This overall overview summarizes the main "dots I'm trying to connect"
throughout this research and I guess a rather long answer to why I
thought the normalized ontology "needed" these XbyY classes.

Lastly, two preliminary ideas in a very early stage, that I gathered
and that I am exploring to capture this classification criteria
meta-knowledge:

* Specialization of OWL Annotation properties given that at the moment
I don't see the need to reason over this type of information.

* A separate RDF or OWL vocabulary to be defined for my purpose,
similar to the OMV (Ontology Metadata Vocabulary) approach[6].

As always, thanks indeed for any comments you or fellow readers may have!

Regards,
Bene

----
[1] Spiteri, 1998. A Simplified Model for Facet Analysis.
http://iainstitute.org/en/learn/research/a_simplified_model_for_facet_analysis.php

[2] Denton, 2003. How to Make a Faceted Classification and Put It On the Web.
http://www.miskatonic.org/library/facet-web-howto.html

[3] John F. Sowa, 2008/06/22:
http://ontolog.cim3.net/forum/ontolog-forum/2008-06/msg00028.html
[4] John F. Sowa, 2008/06/22:
http://ontolog.cim3.net/forum/ontolog-forum/2008-06/msg00034.html
[5] Pat Hayes, 2008/06/23:
http://ontolog.cim3.net/forum/ontolog-forum/2008-06/msg00040.html

[6] Hartman et al., 2005. Ontology Metadata Vocabulary and
Applications. OTM Workshops 2005: 906-915.
Received on Friday, 30 April 2010 12:22:40 GMT

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