Re: The Practical Benefits of the Relational Model

From: Lauri Pietarinen <lauri.pietarinen_at_atbusiness.com>
Date: 6 Oct 2002 15:22:33 -0700
Message-ID: <e9d83568.0210061422.3735a5f6_at_posting.google.com>

> It is often emphasized how beatuful relational theory is, because it
> is based on the set theory. While there is undoubtedly some
> connections, but may I ask why set union is a basic relational
> operator, and intersection is not? (Intersection could be expressed
> via combination of join and projection).

Well, let's look at it this way:

Nobody has the exclusive right to whatever "relational database management system" means. Maybe Oracle, DB2 and SQLServer are decent RDBMS's and there is no need to strive for something more.

Maybe Codd is right in his V2-book.

Maybe Stonebraker got it right...

Maybe implementing the full SQL1999 standard is the holy grail.

Who knows - maybe the OO-guys were right after all...

Date and Darwen have stated there opinion of what an RDBMS should be like in
The Third Manifesto and other books (Selected Writings etc...)

Whatever we may think of what they are saying we now have A CHANCE TO ACTUALLY SEE IF WHAT THEY PROPOSE IS USEFULL, because the guys in Alpora have MORE OR LESS FAITHFULLY
IMPLEMENTED IT (take or leave a few items).

So you can take TTM in your left hand and Dataphor in your right hand and see for your self if Alphora

conforms to TTM

is usefull

Instead of looking at a drawing of a bicycle and debating whether it is possible to
ride such a thing we can ACTUALLY TRY IT OUT in practice.