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From: sakkinen@tukki.jyu.fi (Markku Sakkinen)
Newsgroups: comp.databases
Subject: Re: Postgres (was Re: Public Domain Databases)
Keywords: db  data base database postgress relational
Message-ID: <1990Sep14.065746.5711@tukki.jyu.fi>
Date: 14 Sep 90 06:57:46 GMT
References: <556@mcspdx.pdx.csd.mot.com> <27728@pasteur.Berkeley.EDU>
Reply-To: sakkinen@jytko.jyu.fi (Markku Sakkinen)
Organization: University of Jyvaskyla, Finland
Lines: 31

In article <27728@pasteur.Berkeley.EDU> kemnitz@postgres.berkeley.edu (Greg Kemnitz) writes:
> ...
>What Postgres Is:
>
>o  It is relational.  One of the major goals of Postgres is to show that
>   an essentially relational DBMS can be extended to handle complex objects,
>   rules, and be highly extensible.  Postgres is both relational and is an
>   OODB.

One could say that Postgres is _almost_ relational and _almost_ an OODB,
but not fully either.

Why not really relational: In a relational database, tuples must be
accessible _only_ on the basis of their attribute values.
Postgres adds immutable tuple identifiers that are visible to the user.

Why not really object-oriented: One of the most important requirements
of OO systems in general and OODB's in particular is strong object
identity. The tuple identifiers of Postgres fall short because they
are unique only within a relation (perhaps they can also be reused?).

This is not to deny that Postgres is a highly interesting system.
I have just suggested to a student to do her Master's thesis on it.

Markku Sakkinen
Department of Computer Science and Information Systems
University of Jyvaskyla (a's with umlauts)
Seminaarinkatu 15
SF-40100 Jyvaskyla (umlauts again)
Finland
          SAKKINEN@FINJYU.bitnet (alternative network address)