Re: A good book
From: J M Davitt <jdavitt_at_aeneas.net>
Date: Sat, 08 Jul 2006 11:20:17 GMT
Message-ID: <RxMrg.25305$Eh1.5368_at_tornado.ohiordc.rr.com>
>
> Well, "element" or "member" are both acceptable terms for
> the things that make up a set. In the case of sets that are
> relations, the elements are tuples.
>
> I do regret the accidental use of "table" rather than sticking
> with "relation" as I started with. (D'oh!)
>
> I tend to think of "true proposition" as redundant, but
> there doesn't seem to be a term that would describe
> something that is structurally a proposition but is false.
> So maybe it's reasonable to emphasize it that way.
>
> Is there a distinction between deduction and inference?
> I'm not clear.
Date: Sat, 08 Jul 2006 11:20:17 GMT
Message-ID: <RxMrg.25305$Eh1.5368_at_tornado.ohiordc.rr.com>
Marshall wrote:
> 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.
Deduction and induction are the processes for deriving a specific fact from a collection of facts and vise versa; Inference covers both of them, I think. Plus, in the world of databases, we're seeing the developing notion of "inferential services" so I tend to avoid inference.
> Marshall
Received on Sat Jul 08 2006 - 13:20:17 CEST