Datasheet

❑ A syntax for defining a schema
❑ A syntax for defining a subschema
❑ A data manipulation language
These concepts were later incorporated into the COBOL programming language. They also served as a
base design for many subsequent data storage systems.
IMS
During the same period CODASYL was creating the Network Data Model, another effort was under
way to create the first hierarchical database. During the space race, North American Rockwell won the
contract to launch the first spacecraft to the moon. In 1966, members of IBM, North American Rockwell,
and Caterpillar Tractor came together to begin the design and development of the Information Control
System (ICS) and Data Language/I (DL/I). This system was designed to assist in tracking materials
needed for the construction of the spacecraft.
The ICS portion of this system was the database portion responsible for storing and retrieving the data,
while the DL/I portion was the query language needed to interface with it. In 1968, the IBM portion of
this system (ICS) was renamed to Information Management System, or IMS. Over time, the DL/I portion
was enhanced to provide features such as message queuing, and eventually became the transaction
manager portion of IMS. IMS continued to evolve and was adopted by numerous major organizations,
many of which still use it today.
Relational Databases
Both the Network Data Model from CODASYL and IMS from IBM were major steps forward because
they marked the paradigm shift of separating data from application code, and they laid the framework
for what a database should look like. However, they both had an annoying drawback: They expected
programmers to navigate around the dataset to find what they wanted — thus, they are sometimes
called navigational databases.
In 1970, Edgar Codd, a British computer scientist working for IBM, released an important paper called
“A Relational Model of Data for Large Shared Data Banks” in which he introduced the relational model.
In this model, Codd emphasized the importance of separating the raw, generic data types from the
machine-specific data types, and exposing a simple, high-level query language for accessing this data.
This shift in thinking would enable developers to perform operations against an entire data set at once
instead of working with a single row at a time.
Within a few years, two systems were developed based on Codd’s ideas. The first was an IBM project
known as System R; the other was Ingres from the University of California at Berkeley. During the course
of development for IBM’s System R, a new query language known as Structured Query Language (SQL)
was born. While System R was a great success for proving the relational database concept and creating
SQL, it was never a commercial success for IBM. They did, however, release SQL/DS in 1980, which was
a huge commercial success (and largely based on System R).
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History of Data Access
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