Re: Demo: Modelling Cost of Travel Paths Between Towns
Date: Thu, 18 Nov 2004 16:48:08 GMT
Message-ID: <cn4nd.355005$wV.227943_at_attbi_s54>
"Neo" <neo55592_at_hotmail.com> wrote in message news:4b45d3ad.0411171840.37842293_at_posting.google.com...
> > > Attempts to mask NULLs with unknowns or any other value, don't work
> > > (you must not have read my prior posts expounding the above point).
> >
> > Let's say the users have agreed to use the value 0 to indicate unknown age.
>
> If two things have age 0, is it true or false that their ages are equal?
If we allow for unknown values, then we necessarily must also allow for functions invoked on those unknown values to returns unknown values.
On the other hand, if we treat missing information as explicitly not being there, (a situation that I find slightly preferable) then the sum of an optional age, not present, with another age, not present, results in an optional integer, not present. Cardinality then becomes a different "dimension" as it were to types/values, and we stay 2VL.
Marshall Received on Thu Nov 18 2004 - 17:48:08 CET