RE: 'all resources' is not a set

>-----Original Message-----
>From: pat hayes [mailto:phayes@ihmc.us]
>Sent: Thursday, September 25, 2003 7:31 PM
>To: Larry Masinter
>Cc: public-sw-meaning@w3.org
>Subject: Re: 'all resources' is not a set
>
>
>
>>>  Is the referent of
>>>  'the morning star' and of 'the evening star' the same?
>>>  Not defined.
>
>>  You chose a very bad example to make your case. The whole point of
>>  the example is that it IS well-defined: the answer is yes, they do
>>  have the same referent, viz. the planet Venus (but some people don't
>>  know that, hence the point of the example.)
>
>I may be a little unclear on how 'referent' is being used. If the term
>infers 'the actual object', as in Venus, I guess it's pretty clear.

Yes, that was the original idea of the example. BUt I agree you can 
say that there are two intensional things which happen to have the 
same extension, so that there are three distinct 'ideas' involved. If 
you wanted to have an ontology about ideas rather than astronomy, 
that would make sense.  Either way, however, you can use set theory 
as a foundation. In fact, you can have both ways of thinking and 
still use set theory, as long as you keep the various ideas clear.

>Perhaps
>a better example of what confuses me is my congressman. My intent is to
>assert something about the representative like "he is accountable for X", by
>virtue of his role as a representative. In this case I don't care that at
>the moment my congressman is John Smith, since next year my congressman may
>be Jane Doe. But my assertion still stands. Is this notion of role different
>from the Venus example?

There are lots of examples like this: "The President" (who can change 
from one guy to another every now and then, but is always The 
President), or even things like "the main engine" which might be a 
different piece of machinery after an overhaul but is still the main 
engine.  You can take various positions on what 'things' like this 
really are and how to best describe them, but they pose no particular 
challenge to set theory as a foundation. For example, you can invent 
a category of functional entities, and say that at any given time, a 
functional entity is identical to a unique physical entity, but the 
correspondence might change at various times. (Often, the times or 
events have a special status, eg service outage or inauguration) . Or 
you can invoke an overriding theory of 'continuants' or 'histories' 
or 'eventualities' and base your ontology on those.  But again, all 
of this can be accommodated within a set-theory foundation: in fact, 
all of these have been used in first-order logic-based ontologies.

One way to conflate intermittent things like this to the Venus kind 
of case is to use intensional individuals everywhere. What that means 
in practice, however, is that you often need to say explicitly that 
lots of normal things aren't particularly intensional and don't 
change every now and then; and since there are often more of these 
normal things than the other kind, it is usually easier to treat the 
odd ones as oddities.

Pat

>James Lynn
>Strategic Coordination - Enterprise Standards
>HP Software Services
>610 595 4995


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Received on Friday, 26 September 2003 20:42:41 UTC