Re: A good book

J M Davitt wrote:
> >> In brief:
> >>
> >> Every relation has an associated predicate.
> >> Every element of every table is a proposition.
> >> Every relational algebra expression is an expression of
> >> logical inference, deriving new propositions from existing
> >> ones.
>
> Predicate: good start. "[e]lement of every table:" wrong turn here;
> tuples, not elements, and relation variables, not tables. And not
> merely propositions, but *all* those that has been quantified as true.
> And I think deduction is a better description of relational
> expressions, isn't it?
>
> (Marshall, was that you? I'm surprised...)

Well, "element" or "member" are both acceptable terms for the things that make up a set. In the case of sets that are relations, the elements are tuples.

I do regret the accidental use of "table" rather than sticking with "relation" as I started with. (D'oh!)

I tend to think of "true proposition" as redundant, but there doesn't seem to be a term that would describe something that is structurally a proposition but is false. So maybe it's reasonable to emphasize it that way.

Is there a distinction between deduction and inference? I'm not clear.

Marshall Received on Sat Jul 08 2006 - 07:40:53 CEST