Re: Domains as relations

From: --CELKO-- <71062.1056_at_compuserve.com>
Date: 9 Oct 2002 17:11:34 -0700
Message-ID: <c0d87ec0.0210091611.1f77de90_at_posting.google.com>

>> ... there are two ways to define a relation: by list or by rule...
if there is an accepted mathematical term for what I'm calling "rule based relations". <<

We usually talk about definitions as "intensional" and "extensional"; you give a list of allowed values or you give a characteristic function which can test any candidate value for membership/non-membership.

Then you get in "Godel-land" and have all kinds of questions:

Can I use an infinite list? How do I know a value is or is not in that list?
What if my characteristic function shows only membership? Can I assume all the rejections are not members?
What if my characteristic function shows only non-membership? Can I assume the rejections are all members?

etc. Received on Thu Oct 10 2002 - 02:11:34 CEST

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