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Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 02 Jun 2006 23:13:55 GMT
Message-ID: <TC3gg.16693$A26.385749@ursa-nb00s0.nbnet.nb.ca>


erk wrote:

> Cimode wrote:
>

>>I am sorry but operators are *not* functions (relation model speaking).

>
> What do you mean, "relation model speaking"?

I believe Cimode misspoke. The definition of 'operator' as a symbol signifying an operation is a basic definition in computing--all of computing. You can verify that in the ISO standard definitions if you want to.

>>Each specific combination of operators applied help define a data type.
>>That's all there's to it.

>
> So you're talking about the algebraic definition of a type, like
> pop(push(S, x)) = x for a stack?

No, he is talking about the definition of a type. An algebra simply restricts the operations to those defined only on the type. Algebras have the desirable property of closure, which is very handy for nesting.

Thus, while length and substring are operations on strings--being defined using strings and integers--they are not part of either string or integer algebra. Catenation, on the other hand, is part of the string algebra. Received on Fri Jun 02 2006 - 18:13:55 CDT

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