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Re: SEM: circular primitive vs. defined was Re: was: comprehensiveentailments without dark triples

From: Jonathan Borden <jonathan@openhealth.org>
Date: Mon, 22 Apr 2002 19:14:36 -0400
Message-ID: <026101c1ea53$793cfdf0$0a2e249b@nemc.org>
To: "Dan Connolly" <connolly@w3.org>
Cc: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, "Jeremy Carroll" <jjc@hplb.hpl.hp.com>, <www-webont-wg@w3.org>
Dan Connolly wrote:

>
> I don't understand 'dark triples' well enough to estimate
> their cost at anything lower than 'unbounded'.
> In particular, the costs outlined in
>
>   Problems with dark triples approach
>   From: Jeremy Carroll (jjc@hplb.hpl.hp.com)
>   Date: Wed, Apr 17 2002
>   http://lists.w3.org/Archives/Public/www-webont-wg/2002Apr/0132.html
>
> are unacceptable to me.
>

Gee, I wouldn't want to have to wait 30 or even 3 years for a 'adequate
theory of classes' to be devised before we could do our work. That _would
be_ unacceptable.

Yet Jeremy's message has not convinced me that this would be required.

At the F2F I do recall some discussion that OWL wouldn't grok something
like:

rdf:type daml:subPropertyOf ex:foo

Shrug... I am not sure if this is something that I should care about
(particularly if it is true, as was stated at the F2F, that allowing this
has a large cost in the ability to perform or the efficiency of performing
certain types of inferencing).

Well ok, perhaps we can discuss Jeremy's conclusions:

[[
Personally I would feel happier with that solution than paying either of the
prices that my analsysis suggests for a dark triple based theory of classes:
viz:
either:
- a significant delay to the WG product in order for the SEM focus area to
undertake a research project
or:
- the inability to meaningful take a subPropertyOf the properties used in
constructing an owl ontology.
]]

Does the SEM focus group agree on the first point?
What is the practical effect of the second point?

>
> > Is primitive vs.
> > defined simply an 'implementation' mechanism of reducing the number of
> > classes a thing belongs to? i.e. are "defined" classes, classes that you
are
> > telling the system that you want it to make inferences on etc.?
Otherwise
> > what is the harm of letting things be members of the instance sets of
> > primitive classes?
>
> There's no harm; I just didn't think you meant to say that there
> were no other conditions for being in the PaternalDominantInheritance
> class... I presume one has to actually have some disease
> to be in that class.
>

This says that one has to have a father who is a member of the class to be
in the class. I suppose a primitive class can't have members which aren't
also members of some sub class of the primitive class? So a defined class
has 'direct' members and a primitive class has members via the inheritance
chain? There must be a reason to make this distinction, but aside from some
sort of efficiency issue, I don't see it -- I am not asserting that there is
no distinction, I honestly don't quite understand it.

Jonathan


Jonathan
Received on Monday, 22 April 2002 19:18:23 GMT

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