Re: Do Data Models Need to built on a Mathematical Concept?

> A (binary) relation is a subset of a Cartesian product.

Yes, you are in synch with text books.
Schaum's Outline explains binary relation as follows: A = (b,c)
B = (j,k,l)
AxB = ((b,j), (b,k), (b,l), (c,j), (c,k), (c,l)) then (b,j), (b,k) ... are binary relations.

This is INCORRECT because it misses the fundamental form of a binary relation.
(b,j) is NOT a single binary relation.
(b,j) is composed of TWO binary relations. First, b is related to A, b has a relation to A. Second, j is related to B, j has a relation to B.

They will have to rewrite the books and take back some diplomas or more likely they will keep the current inaccurate definitions which makes my experience on google all the more interesting :) Received on Sun May 04 2003 - 17:58:44 CDT