Does Codd's view of a relational database differ from that of Date & Darwin? [M.Gittens]

From: mountain man <hobbit_at_southern_seaweed.com.op>
Date: Wed, 01 Jun 2005 12:27:30 GMT
Message-ID: <SQhne.9308$BR4.3785_at_news-server.bigpond.net.au>

Last year there was this thread with the subject line of "Issues with the logical consistency of The Third Manifesto", in which opinions were expressed about Maurice Gittens paper 'A critical reading of the Third Manifesto' (available at http://www.gits.nl/)

I did not read *all* of the responses, but notice that many found the original article too long. There actually now exists a very small (4 page) update entitled "A Codd inspired amendment ..." on Maurice Gittens site (above) which may have escaped the attention of some.

In this subsequent article, the author makes the assertion that Codd's view of a relational database differs from that of Date and Darwin.

Here is the relevant quote:

======[quoting M.Gittens]=====================

According to E.F. Codd a relational database is defined as:

"A relational database is a time-varying collection of data,
    all of which can be accessed and updated as if they were     organized as a collection of tabular time-varying tabular     (nonhierarchic) relations of assorted degrees defined on a     given set of simple domains."

According to the Third manifesto:

"The question as to what data types are supported is orthogonal
    to the question of support of the relational model."

Let us take time to notice the fundamental difference between the two positions presented here. As a result of the position that support for the relational model is orthogonal to the supported data types, The Third Manifesto proceeded to allow domains to have an arbitrarily complex structure and also to support arbitrarily complex user defined operators.

Codd on the other hand specifically states that relational databases must be based on "simple" domains. Codd also says that domain values should not be decomposable further by the DBMS. Which is to say: According to Codd, the question as to what data types are supported is not orthogonal to the question of support of the relational model. Based on this evidence one can but conclude that Codd's view of relational database is logically different from The Third Manifesto's view of a relational database. Such logical differences are big differences.

======[end quoting M.Gittens]==================

Any opinions on this POV?

-- 
Pete Brown
IT Managers & Engineers
Falls Creek
Australia
www.mountainman.com.au/software

Received on Wed Jun 01 2005 - 14:27:30 CEST