Re: cdt
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Sun, 06 Jun 2004 16:21:28 +0200
Message-ID: <40c32861$0$559$e4fe514c_at_news.xs4all.nl>
>
> Not if you know the difference between implicit and explicit, which you have
> provided by example, below. Implicit is implied, explicit is expressed.
> Implicit is correct in this case. I'm fairly sure Drs. Elmasri and Navathe
> carefully considered which word to use, and that their editor reviewed it
> somewhere during the process of creating three editions of the book. Try,
>
> Known facts that can be recorded and have _an implied_ meaning.
>
> They're not explicit until after they've been recorded (or stated, i.e.,
> expressed).
>
Date: Sun, 06 Jun 2004 16:21:28 +0200
Message-ID: <40c32861$0$559$e4fe514c_at_news.xs4all.nl>
Alan wrote:
> Laconic2 wrote:
>>Perhaps the problem lies in the word "implicit", in the term "implicit >>meaning". Perhaps what is implicit is subject to misinterpratation.
>
> Not if you know the difference between implicit and explicit, which you have
> provided by example, below. Implicit is implied, explicit is expressed.
> Implicit is correct in this case. I'm fairly sure Drs. Elmasri and Navathe
> carefully considered which word to use, and that their editor reviewed it
> somewhere during the process of creating three editions of the book. Try,
>
> Known facts that can be recorded and have _an implied_ meaning.
>
> They're not explicit until after they've been recorded (or stated, i.e.,
> expressed).
>
>>Back in the days before databases, when COBOL programmers stored data in >>records in files, the records had an "implicit" record definition. The >>COBOL programmer needed to include the correct record definition in the >>program in order to read the data. By including the data definitions in >>By including the data definitions in the >>schema, and putting the schema in the database, the definitions were made >>"explicit" rather than "implicit".
Column names, table names hint at meaning, they do not really define.
It does not help rephrasing this in relational terms: The names of attributes and relational variables don't do a better job at defining. The meaning of the propositions conveyed by the tuples is supposed to be explained by the *external* predicate (3rd manifesto, 1st edition). "external" suggests that the authors do not think of the predicate as being part of the database - but I can't check this as I don't have the book here. The "definitions" in the schema only serve to associate the structure of the relation body with the relation header. Received on Sun Jun 06 2004 - 16:21:28 CEST