Re: evolution of relational database

From: Jan Hidders <hidders_at_REMOVE.THIS.win.tue.nl>
Date: 21 Nov 2000 14:05:30 GMT
Message-ID: <8vdvfa$llr$1_at_news.tue.nl>


David wrote:
> [...] So, can anyone help me to understand the set theory and how it
> brought about relational databases?

The term "brought about" is perhaps not the right one. The issue is why Codd used the term "relation" and not how he got his ideas. The reason is that this term was at the time already used in set theory to describe a certain type of set. as follows. A relation over the sets A and B is a set consisting two-tuples <a, b> such that a is in A and b is in B, and a relation over A, B and C is a set consisting of three-tupels <a, b, c> such that a is in A, b is in B and c is in C. Et cetera.

As you already saw in Codd's paper this is exactly how he wanted to represent data so that is why he decided tot use the term "relation".

If you ask what "brought about" the relational model then it is my opinion that the anser should be 'predicate logic', as Codd also explains himself in Section 1.5.

Kind regards,

  • Jan Hidders
Received on Tue Nov 21 2000 - 15:05:30 CET

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