Re: Demo: Modelling Cost of Travel Paths Between Towns

"Marshall Spight" <mspight_at_dnai.com> wrote in message news: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

> >
> > 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
>
>

I do not disagree, in fact I also prefer the "not present" option for the reasons you state. I was just trying to avoid using nulls because someone here insists that it could not be done. Received on Thu Nov 18 2004 - 22:36:54 CET