Databases Reference
In-Depth Information
The Evolution of the Relational Database
The relational database concept was described first by Dr. Edgar F. Codd in an IBM
research publication entitled “System R4 Relational” that was published in 1970. Ini‐
tially, it was unclear whether any system based on this concept could achieve commercial
success. Nevertheless, a company named Software Development Laboratories Rela‐
tional Software came into being in 1977 and released a product named Oracle V.2 as the
world's first commercial relational database within a couple of years (also changing its
name to Relational Software, Incorporated). By 1985, Oracle could claim more than
1,000 relational database customer sites. Curiously, IBM would not embrace relational
technology in a commercial product until the Query Management Facility in 1983.
Why did relational database technology grow to become the de facto database technol‐
ogy? A look back at previous database technology may help to explain this phenomenon.
Database management systems were first defined in the 1960s to provide a common
organizational framework for data formerly stored in independent files. In 1964, Charles
Bachman of General Electric proposed a network model with data records linked to‐
gether, forming intersecting sets of data, as shown on the left in
Figure 1-1
. This work
formed the basis of the CODASYL Data Base Task Group. Meanwhile, the North Amer‐
ican Aviation's Space Division and IBM developed a second approach based on a hier‐
archical model in 1965. In this model, data is represented as tree structures in a hierarchy
of records, as shown on the right in
Figure 1-1
. IBM's product based on this model was
brought to market in 1969 as the Information Management System (IMS). As recently
as 1980, almost all database implementations used either the network or hierarchical
approach. Although several competitors sold similar technologies around 1980, only
IMS could still be found in many large organizations just 20 years later.
Figure 1-1. Network model (left) and hierarchical model (right)
