Re: CODASYL-like databases

From: Rob <>
Date: Wed, 2 Apr 2008 08:10:17 -0700 (PDT)
Message-ID: <>

Sorry. After rereading your post and my response, I realize my effort to be concise resulted in confusion. Here are 3 statements:

  1. > > RDBMSes are sometimes described as a reaction against network-/
    hierarchical databases. ("Troels Arvin" <>)

I agree with this wrt hierarchcial dbms's, not network. In 1970, hierarchical dbms products were everywhere, network dbms products hardly existed. Codd's relational model and the CODASYL/DBTG network proposals were both reactions to maintenance/management problems with hierarchical products. The relational model prevailed.

2. > I would describe the introduction of the relational model of data for DBMS
work as forward progress rather than as a reaction against something. ("David Cressey" <>)

Here I do disagree. The relational model was revolutionary thinking. Before 1970, database management wasn't even a computer science concept. Until at least 1974, SIGMOD was SIGFIDET-- Special Interest Group on File Description & Translation. Perhaps my "disagreement" is based on my personal experience of that time: IMS and all it's lookalikes were uninteresting data processing products; the relational model was a giant leap forward that was worthy of interest to a computer scientist. You imply "evolutionary" -- I need "revolutionary".

3. > The early RDBMS products were, to some extent, an attempt to obtain the power and simplicity of the relational model without discarding a code base that had been based on hierarchical or network models of databases. ("David Cressey" <>)

Wrt codebases, the only contribution from hierarchical systems were the Access Methods (ISAM, VSAM, ...). Wrt network systems, the only reused code I know of (from your postings) were the DEC products. In the grand scheme of things, these hardly appeared on the radar screen. (That is not meant to disparage your knowledge or experience: I was the system architect on a RDBMS in 1980-84 and designed the optimizing compiler for another RDBMS in 1985. I guarantee you nobody remembers either!)

Not really that much disagreement here, just differences in perspective.

Cheers, Rob Received on Wed Apr 02 2008 - 17:10:17 CEST

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