Re: Validating daml+oil-ex.daml

From: Pat Hayes (
Date: 11/01/01

>From: Frank van Harmelen <>
>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.


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, 
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