RE: [OEP,ALL] Potential topics for OEP notes

Fabien, and all

A few remarks about multiple instantiation, since uncontrolled usage of it by data
providers lately caused some severe problems lately in one of our customer's data base.

Not to speak about consistency issues involved, some (many? most?) ontology-driven GUI
(e.g. Mondeca ITM, Protégé ... ) have  interfaces built dynamically, for each class of
objects, from the properties of which domain contains the class. For such GUI, multiple
instantiation is really a no-no, at least in edition. Try to import in Protégé an
individual with multiple rdf:type declarations. It might be imported successfully, most of
the time it will, you will *see* it in all the relevant classes, but you won't be able to
*edit* it (only to delete it). We have the same behavior in ITM GUI.

And of course, through those interfaces, you can't create an individual with multiple
classes ...

Another thing is that identification of individuals is often a two-step process involving
the class where two objects are considered identical if:
1. They are instances of the same or equivalent class(es) and
2. Some set of "identifying properties" is the same.
In such process, multiple instantiation can be an issue by blocking step 1.

So, if multiple instantiation is possible, users need to be aware of the consequences in
terms of applications able to manage it. As for your example, note that in Topic Maps
ontologies, roles and classes are different animals, which allows to deal with multiple
roles without without using multiple instantiation :)

So I would suggest to put multiple instantiation in a note for "advanced users", with all
the needed caveats.

Regards

Bernard


**********************************************************************************

Bernard Vatant
Senior Consultant
Knowledge Engineering
bernard.vatant@mondeca.com

"Making Sense of Content" :  http://www.mondeca.com
"Everything is a Subject" :  http://universimmedia.blogspot.com

**********************************************************************************

> -----Message d'origine-----
> De : public-swbp-wg-request@w3.org
> [mailto:public-swbp-wg-request@w3.org]De la part de Fabien Gandon
> Envoyé : mercredi 20 octobre 2004 09:48
> À : public-swbp-wg@w3.org
> Cc : public-swbp-wg-request@w3.org
> Objet : Re: [OEP,ALL] Potential topics for OEP notes
>
>
>
> Hi,
>
> Christopher Welty a écrit :
> >  > - a design pattern on the "usage of multiple instantiation": avoid
> >  > artificial multiplication of common subtypes, useful to model roles, can
> >  > be used for boolean properties in closed worlds, etc.
> >
> > I'm not sure what you mean - do you mean that an individual can be an
> > instance of more than one class?
>
> Exactly. Students are puzzled by this ability to declare multiple
> classes for an object and they were struggling to understand why and
> when it should be used.
>
> Examples using roles worked well: we instantiated a "abc:Firm" and
> reused its URI to instantiate its roles in business exchanges
> "abc:Provider", "abc:Customer".
>
> We also saw that multiple instantiation allows us to formalize Boolean
> attributes as classes (since they are unary predicates) without creating
> all the possible combinations of sub classes:
> "abc:FirmWithRAndDDepartment", "abc:RegisteredFirm", etc. And we talked
> about the closed world assumption one must make if one wants to use
> negation as failure to determine those instances for which the property
> is false.
>
> I am sure there exist good practices in using multiple instantiation and
> typical situations where it offers elegant solutions; however, in my
> experience, students with a background in object-oriented programming
> rarely envisage this option since they are not familiar with it.
> I was wondering if it wouldn't be a good idea to have one or more design
> patterns showing typical modelling situations (ex: roles) were multiple
> instantiation is both natural and elegant.
>
> Just my 2 cents,
>
> Fabien
> --
> "Proving that I am right would be admitting that I
>   could be wrong."                 -- Beaumarchais.
>   ____________
> |__ _ |_  http://www-sop.inria.fr/acacia/personnel/Fabien.Gandon/
> |  (_||_) INRIA Sophia Antipolis - ph# (33)(0)4 92 38 77 88
>

Received on Wednesday, 20 October 2004 08:38:57 UTC