Re: 3 value logic. Why is SQL so special?

Marshall skrev:

> Bob Badour wrote:
> >
> > Can we agree that the algebra of nullable<boolean> is not boolean
> > algebra and is not 2-valued logic?
>
> Interesting point. On the face of it, any 3VL is not a boolean algebra
> because 3 is not a power of two, and all boolean algebras have
> a power of two elements. I've long been appreciative of the fact
> that, for example, the truth table for AND is 9 cells in 3VL instead
> of four for 2VL. And the fact that while there are only 16 distinct
> binary functions in 2VL, but, uh, crap. What's that number again?
> Oh, yeah: 19683 distinct binary functions in 3VL.[1] So the complexity
> goes up a *lot.*

Right. I presume you also have problems multiplying two three-digit decimal numbers?

>
> But this is a really good point: you also give up all the theorems
> of the boolean algebra! I mean, some of them might still hold,
> but which ones? You have to check every one over again.
>
> Wow.
>
Wow indeed. Just impossible ;-)

/Peter Received on Fri Sep 22 2006 - 10:19:09 CEST