Path: utzoo!attcan!uunet!cimshop!davidm From: cimshop!davidm@uunet.UU.NET (David S. Masterson) Newsgroups: comp.databases Subject: Re: Postgres (was Re: Public Domain Databases) Message-ID: Date: 17 Sep 90 04:56:17 GMT References: <556@mcspdx.pdx.csd.mot.com> <27728@pasteur.Berkeley.EDU> <1990Sep14.065746.5711@tukki.jyu.fi> Sender: davidm@cimshop.UUCP Organization: Consilium Inc., Mountain View, California. Lines: 27 In-reply-to: sakkinen@tukki.jyu.fi's message of 14 Sep 90 06:57:46 GMT In article <1990Sep14.065746.5711@tukki.jyu.fi> sakkinen@tukki.jyu.fi (Markku Sakkinen) writes: 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. Hmmm, doesn't the immutable tuple identifier agree with Codd/Date's RM/T database model with system generated primary keys? Might not an tupleID be considered just another attribute value? 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?). What is Postgres' definition of an object instance? Does it correspond to a tuple? (I haven't seen Postgres, yet). -- ==================================================================== David Masterson Consilium, Inc. uunet!cimshop!davidm Mtn. View, CA 94043 ==================================================================== "If someone thinks they know what I said, then I didn't say it!"