Re: A different definition of MINUS, Part 3

From: paul c <>
Date: Sat, 20 Dec 2008 14:03:58 -0800
Message-ID: <kYd3l.75580$zQ3.51838_at_newsfe12.iad>

Cimode wrote:
> There are a lot of problems related to deriving a language definition
> directly from traditional algebra, one of them being determining a
> semantics that maps to RL traditional formalism in an exhaustive
> fashion, while remaining effective to be expressed semantically by a
> programmer. Since defining a language does not answer the same
> problem than establishing a theorem, it is difficult for me to imagine
> they could both be similar solutions.
> ...

I think those are profound observations. I imagine it is easy for a designer to fall into the trap of designing a language for the algebra instead of designing a language for the purposes in mind. For example, Codd wrote very little about his calculus and algebra per se compared to everything else. From the get-go, he had various operators called JOIN.   For all I know, he did not think his join was defined by the TD join and so not by the A-algebra A <AND> B definition. We all must die and of course I don't like the idea but in his case we all have an especial reason to be sorry he is dead. I met him once, just as his book was coming out, but I was so completely ignorant about the relationship of the calculus to the algebra that I didn't think to ask him any questions about that. Although I knew a bit of the calculus, I hadn't made the algebra connection and the standard advice I gave to journeymen Cobol programmers and such was very crude, having to do with I then called 'regular' sentences. Strangely enough, people whose native languages wasn't English seemed to me to do better with this advice than the native speakers. Received on Sat Dec 20 2008 - 23:03:58 CET

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