Re: more on delete from join

From: Mr. Scott <do_not_reply_at_noone.com>
Date: Wed, 26 Aug 2009 22:18:37 -0400
Message-ID: <OpydnVmGqt5gcQjXnZ2dnUVZ_uydnZ2d_at_giganews.com>


"paul c" <toledobythesea_at_oohay.ac> wrote in message news:RYhlm.40820$Db2.17042_at_edtnps83...
> Mr. Scott wrote:
>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
> ...
>>> Insert to a base relvar represents a conclusion: R =: R UNION A conludes
>>> R AND A.
>>
>> It concludes R OR A. R AND A would be just A, provided A is in R.
>
> I think you mean R <AND> A would be just A, provided A is in R and they
> have the same heading. Whether or not A is in R, after the assignment,
> all propositions that A stands for and all propositions that R previously
> stood for are true, eg., if r1,r2,...,rn and a1,a2,...,an are the original
> propositions, r1 AND r2 AND ... a1 AND a2 is true as far as R is
> concerned. .

I mean R OR A. Under the closed world interpretation, the disjunction of the collection of facts represented by a table is interpreted as the conjunction of those facts along with the negation of the facts represented by the complement of the table, the assumption being that what is stated is supposed to be true and what isn't isn't. I mean R OR A because the disjunctions of the collections of facts represented in R and in A are combined into the disjunction of a single collection of facts prior to applying the closed world interpretation. Received on Thu Aug 27 2009 - 04:18:37 CEST

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