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Re: Relationals vs. Objects Databases I

From: Jeremy Rickard <Jeremy_at_SPAM.demon.co.uk>
Date: 1998/01/19
Message-ID: <+eizgAALp7w0Ew$k@jbdr.demon.co.uk>#1/1

In article <34C371A9.3ECF_at_ipipan.waw.pl>, Kazimierz Subieta <subieta_at_ipipan.waw.pl> writes

>> So how about object-relational? Does it not "fix" some of these issues?
>
>Yes, some issues are fixed and some new are introduced. The question is
>what means "relational" in "object-relational"? Does it mean they
>apply the relational theory? Does it mean they follow the Codd's
>relational model? This is a nonsense, the association with Codd and
>mathematics is lost more than 10 years ago. In "relational" SQL3 we
>have a lot of stuff that Codd never dreamed about: ADT-s,
>complex structures as elements of tuples, persistent tuple identifiers
>that can be used as pointers (the heresy in the relational
>model!), etc. Eclectic monster that swallows every buzzword
>flying in the air.
>
>"Relational" in "object-relational" means nothing. (Hence we can
>shorten "object-relational" it to "object", if you like.)
>There is no ideological difference between object DBMS and
>object-relational DBMS.

I diagree. Object-relational databases are still essentially relational. The "object" bits are very much a "black box" add-on. Particularly important in my view is the fact that the structure of the complex datatypes is not known to the optimiser - from the DBMS point of view it's just another base datatype. Similarly, the only important thing the optimiser knows about UDF's is the (estimated) cost of executing them.

This at least is the current situation with DB2. IBM have moved quite conservatively, and carefully kept this distinction - in my view rightly.

Of course, some products do seem to be getting more object-orientated. Oracle does support pointers, and (I believe) non-atomic datatypes can be declared. I would agree that does make it a bit of an eclectic monster, although in truth the object functionality is still very much an add-on.

The core relational functionality provided by these products is perfectly able to satisfy most business needs. I see the object extensions as icing on the cake, not a total revolution.

-- 
Jeremy Rickard

(To email, change "SPAM" to "jbdr" in address.)
Received on Mon Jan 19 1998 - 00:00:00 CST

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