Re: 4 the Faq: Strengths and Weaknesses of Data Models

From: Laconic2 <laconic2_at_comcast.net>
Date: Fri, 15 Oct 2004 08:06:35 -0400
Message-ID: <3Z6dnbE4VanFIPLcRVn-pw_at_comcast.com>


"Marshall Spight" <mspight_at_dnai.com> wrote in message news:E4Hbd.260473$3l3.250666_at_attbi_s03...
> "Laconic2" <laconic2_at_comcast.net> wrote in message
news:AvCdnQKK88xZWfPcRVn-vw_at_comcast.com...
> >
> > Of course, DEC SW engineering interpreted "relational DBMS" in ways
that
> > some in this crowd dismiss as heretical or, even worse, commercial. Now
ask
> > me if I care.
>
> Tell, tell! *What* did they do to the RDM that was heretical and/or
> commerial? Was it good or bad?

Well, for starters, their terminology was a strange mix of relational jargon, and traditional files and records jargon. In versions one and two of the product, they referred to "relations, records, fields, and global fields", instead of "tables, rows, columns, and domains". This kind of terminology drives people like Joe Celko right up the wall.

They added support for SQL in version 3. I think they wanted to compete with IBM. Just using SQL as an interface is enough to earn the wrath of the relational bigots around here.

It was possible to define a "relation" that would violate 1NF.

They had a datatype called "DBKEY". This was really a pointer. This meant that you could build your own network or hierarchical database underneath the relational database if you wanted to. DBKEYs stored in records suffer from all the problems with the graph data model that are outlined in the theory. But they were blazingly fast!

Their DML was really not a PL. In order to do "real programming", you needed a "real programming language".

This is off the top of my head. I might think of more, later. Anyway, all the people in here who dismiss the commercial relational DBMS products of the early 1980s as "not relational" would have done the same think with Rdb, I imagine.

There are several things that I think, in retrospect, they could have done better. But there are an enormous number of things they got right, and that I just took for granted, because it was my first DBMS! Received on Fri Oct 15 2004 - 14:06:35 CEST

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