From: Pat Hayes (phayes@ai.uwf.edu)
Date: 11/01/01
>From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl> >Subject: Re: Validating daml+oil-ex.daml >Date: Thu, 01 Nov 2001 00:08:57 +0100 > >> Jeff wrote: >> >> > > 2) The Person class has a restriction stating the a person can have only >> > > one FullTimeOccupation, but FullTimeOccupation is not defined in the >> > > ontology. The FullTimeOccupation class should be added to the ontology. >> >> Peter answered: >> >> > It probably should be, but it is not strictly necessary, as its >>position in a >> > restriction makes it an rdf:Class. >> >> We've discussed this a few times in the past. It was then >>considered a deliberate feature of the example to show that >>DAML+OIL allows the usage of (e.g.) classes before they are >>"defined", or even when they are not "defined" at all (particularly >>in a Web context). >> >> I still consider this a feature of the example, not a bug. >> >> Frank. >> ---- >> >I had forgotten this discussion, and I agree with Frank (feature, not bug). I agree with this also. Pat PS. However, we perhaps do need to acknowledge the tension mentioned earlier between checking for 'integrity' and checking for inconsistency. I am sure that it would be of great utility for many folk to have tools that would check for a number of conditions that are consistent but suggest, pragmatically, that something may be wrong and needs to be fixed. The same tension comes up even in AI work, where some folk want tools that 'catch' logically meaningful expressions that are nevertheless usually input errors, such as expressions of the form (forall (?x) (iff P Q)) where P does not contain ?x, which probably should have been (iff P (forall (?x) Q)). So I think we should encourage people to build pragmatic oddity-flaggers of various useful kinds, just as long as we insist on being very clear about the differences between syntactically illegal, semantically inconsistent, and pragmatically peculiar. 'validating' is such a loose term that it could mean any one of these, unfortunately. -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
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