Re: 3vl 2vl and NULL
Date: Mon, 12 Dec 2005 16:52:15 +0200
Message-ID: <dnk2r6$hr1$1_at_domitilla.aioe.org>
"JOG" <jog_at_cs.nott.ac.uk> wrote in message
news:1134395485.579347.115980_at_g43g2000cwa.googlegroups.com...
> David Cressey wrote:
> > There is a 3VL whose values are [TRUE,FALSE,MEANINGLESS] when a formula
> > comes up MEANINGLESS, it means that it is not a "well formed formula"
or
> > WFF. The definition of a WFF is outside this discussion. But an
assertion
> > of MEANINGLESS is a denial of TRUE and FALSE.
>
> Hi David, am I correct in saying that in a domain like {1,2,3,null}
> something like 1<null is an example of one of these non-WFF? With an
> ordering like < db's always assume that the domain is totally
> orderered, but with the inclusion of null we now have a partially
> ordered set, as null is logically incomparable to anything else in the
> set - it is this incomparability that means non-WFF can emerge.
If we take n to be the equivalence class of sets with n elements, then a<b
can be interpreted as there exists A in a and B in b with A proper subset of
B.
If we take null to be the equivalence class of sets with the same number of
elements as natural numbers then what is the truth value of 1 < null ?
Received on Mon Dec 12 2005 - 15:52:15 CET