Right (01)
Sent from my iPhone (02)
On Jul 27, 2009, at 8:25 AM, "Christopher Menzel" <cmenzel@xxxxxxxx>
wrote: (03)
> On Jul 26, 2009, at 8:17 PM, Dave McComb wrote:
>> We teach a class in OWL. My sense from our students confusion is
>> that the main point of departure between what you understand and
>> what's occurring in an ontology comes down to the distinction
>> between intensional and extensional sets.
>
> Dave, I think the distinction here is better cast as the difference
> between intensional and extensional *definitions* of sets.
> "Intensional set" seems to me to be an oxymoron, as sets are by
> definition extensional, i.e., Set1 = Set2 iff every member of Set1 is
> a member of Set2. However, one and the same set can be *defined*
> intensionally, i.e., by means of a description (e.g., {x | x is a US
> Senator from Texas}) that might in fact pick out *different* sets at
> different times, or extensionally, i.e., by simply listing its members
> (e.g., {John Cornyn, Kay Bailey Hutchison}).
>
> -chris
>
>
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