Re: CODASYL-like databases

> In his 1980 paper "DATA MODELS IN DATABASE MANAGEMENT", Codd points
> out (under HISTORY OF DATA
> MODEL DEVELOPMENT) that "[h]ierarchical and network systems were
> developed prior to 1970, but it was not until 1973 that data models
> for these systems were defined."

Interesting comment that's open to interpretation based on how you define a data model.

The network model that emerged from the CODASYL Data Base Task Group was derived from GE IDS, much as today's XQuery was derived from Quilt. Charles Bachman's IDS was released by GE in 1965. Bachman and Codd were both recipients of the ACM Turing Award and they faced off in a famous 1970s debate about navigational vs. relational data access.

The CODASYL network model is much like a persistent representation of a doubly-linked list. That model for traversing lists was well-known before the CODASYL spec of 1971. Linked lists date back to the 1950s. They were supported by LISP in the 1960s, and were described in Knuth's writings.

> Personally, I believe that the Relational Model prevailed because SQL
> was more natural (read: English-like) and non-procedural whereas the
> CODASYL sublanguage(s) were programmatic and navigational.

Before Boyce and Chamberlin developed SQL, there were earlier attempts to develop English-like query languages - including a query language that came from IBM in the 1960s.

In 1968 the head of our systems center was part of the CODASYL committee, so we looked closely at the "data base" (database) systems that existed at the time. He'd been a consultant involved in field testing IBM's Generalized Information System (GIS) at Royal Dutch Shell in Venezuela in 1966. GIS used very simple English-like commands designed for non-programming users. Received on Thu Apr 03 2008 - 21:23:57 CEST