Re: The Fact of relational algebra (was Re: Clean Object Class Design -- What is it?)

"Leandro Guimarães Faria Corsetti Dutra" <leandrod_at_mac.com> wrote in message news:3BBBBEEE.30906_at_mac.com...
> > I seem to remember the rdbms guys redefined 'completeness', to something
> > that has no bearing on mathematical compeletness (which I cant remember
the
> Can you expand on that?

I think completeness means that the language can express any 'computable function'. For example, it can express the square of a number, since that is computable.

> What "fundamental concepts" do you think that relational algebra
redefines?

I found this definition of "relation" on a maths page on the net:

• relation : (logic, set theory) a correspondence between two sets (say A, B) represented by a set of ordered pairs, each containing one element from A and one from B.

Implying you have to normalise everything into binary relations before it looks anything like the above definition.

A good example of a relation is the greater-or-equal-to sign >= It would be 'implemented' in set theory as an infinite set containing all the numbers,

{(0,0),(0,1),(0,2),.......(1,1),(1,2),(1,3),...........}

Of course we don't have infinitely big sets in computers, so we implement it using an algorithm.

Daniel Received on Thu Oct 04 2001 - 13:53:08 CEST