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[protege-discussion] modal logics

Nick Drummond nick.drummond at cs.manchester.ac.uk
Tue Jun 3 08:22:18 PDT 2008


Hi Emmanuelle.
This is a big topic. You might want to do a google search on "ontology
sanctioning" as this is often a term used to describe the things that are
extra-ontological, but are commonly used in querying and application
building.

Nick

2008/5/30 Thomas Schneider <schneidt at cs.man.ac.uk>:

> Hi Emmanuelle,
>
> I'll try to give an answer from a logician's point of view. You might
> need to translate my OWL-Manchester syntax into
> Protégé-Frames syntax---or maybe
> someone else here can do this please?!?
>
> On 29 May 2008, at 13:37, Emmanuelle Pellegrino wrote:
>
> > Dear Colleagues,
> >
> > We are developing an ontology of architecture. The architect
> > conceives a project and thus not only existing real objects, but
> > virtual objects.
> >
> > Consequently, one puts the question to know how to treat modal
> > logics with Protégé.
>
> Well, modal logics (ML) aren't so much different from description
> logics (DL), and I don't see why modal logics are necessary here:
> can't you say things about objects that aren't explicitly named in
> your ontology using DLs, too?
>
> > In Protégé, one can put existential
> > or universal restrictions on classes ; these restrictions are of a
> > kind obligatory. To be member of a class, one must [necessarily]
> > have at least this or that (existential restriction) or only this or
> > that (universal restriction).
> >
> > For the moment, therefore, one can say :
> > "Must have at least"; "must only have"
> > "Must be at least"; "must be only"
> > → character of necessity
>
> Yes, for instance:
>
> Human implies hasPart some Leg
> Human implies hasAncestor only Human
>
> > We would like to pass from the necessary field to the possible field.
> >
> > In other words, how to bring restrictions on classes which
> > don't have all an obligatory character?
> >
> > And in complement, to express the opposite of the necessity,
> > contingency :
> > "Not to have to be"
> > "Not to have to have"
> > → character of what is contingent (not-necessary)
>
>  From your explanation, it seems to me that, by "opposite", you refer
> to the negation of necessity? So you don't seem to need any new
> modality, just some sort of negation. Suppose you want to express the
> "opposite" of
>
> Animal implies hasPart some Leg ,
>
> because not all animals *need* to have a leg. This means that there
> are animals that have no legs, hence the classes "Animal" and "not
> (hasPart some Leg)" are not disjoint. This requires quite some
> expressivity, for instance individuals in the terminological part of
> your ontology:
>
> dummyIndividual implies Animal and not (hasPart some Leg)
>
> What exactly do you want to express in your ontology?
>
> > To express the possibility :
> > "To be able to be"; "must not not to be"
> > "To be able to have"; "must not not to have"
> > → character of possibility
>
> What's the difference between possibility and contingency in your
> scenario? From my abstract point of view, they look the same. An
> animal does not need to have a leg if (and only if) it is able to have
> no legs, which can be expressed by the previous axiom.
>
> > And in complement, the opposite of the possibility, impossibility :
> > "Not to be able not to be", "Must not be"
> > "Not to be able not to have", "Must not have"
> > → character of impossibility
>
> Through the abstract glasses again, impossibility looks the same as
> necessity: If it's impossible that humans have no legs, it's necessary
> that they have a leg---and vice versa.
>
> > In architecture, to put the question of the description of the
> > necessary or possible character of a restriction reverts at the
> > bottom raising the question of a combinatory of the possible. The
> > combinatory is the even fact of opening on possibilities. To combine
> > supposes to select in various paradigms each time a paradigmatic
> > element (one chooses this one or that one). Then the various
> > paradigmatic elements selected are connected. One places this
> > element in this place and this other at that one[1].
>
> I'm sorry, I can't quite follow this explanation. What are you trying
> to say? I'd like to see concrete examples of what you want to express
> in your ontology.
>
> Hope this has helped a bit.
>
> Cheers
>
> Thomas
>
> +
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> schneider at cs.man.ac.uk |
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