CODASYL

CODASYL (often spelt Codasyl) is an acronym for "Conference on Data Systems Languages". This was an Information technology industry consortium formed in 1959 to guide the development of a standard programming language that could be used on many computers. This effort led to the development of COBOL.

CODASYL's members were individuals from industry and government involved in data processing activity. Its larger goal was to promote more effective data systems analysis, design, and implementation. The organization published specifications for various languages over the years, handing these over to official standards bodies (ISO, ANSI, or their predecessors) for formal standardization.

History

CODASYL is remembered almost entirely for two activities: its work on the development of the COBOL language (whose history is described in the article on COBOL), and its activities in standardizing database interfaces. It also worked on a wide range of other topics, including end user forms interfaces and operating system control languages, but these projects had little lasting impact.

The remainder of this section is concerned with CODASYL's database activities.

In 1965 CODASYL formed a List Processing Task Force. This group was chartered to develop COBOL language extensions for processing collections of records; the name arose because Charles Bachman's IDS system (which was the main technical input to the project) managed relationships between records using chains of pointers. In 1967 the group renamed itself the Data Base Task Group, and its first report in January 1968 was entitled COBOL extensions to handle data bases.

The "set", the basic structure of the CODASYL database model. A set consists of one owner record and n member records (these are labeled as "parent" and "child" in the diagram, but the Codasyl terminology is "owner" and "member"). In the above example, we were looking at a basic set which embodies a 1:N (Owner:Member) relationship.^[1]

In October 1969 the DBTG published its first language specifications for the network database model which became generally known as the Codasyl Data Model. This specification in fact defined several separate languages: a data description language (DDL) to define the schema of the database, another DDL to create one or more subschemas defining application views of the database; and a data manipulation language (DML) defining verbs for embedding in the COBOL programming language to request and update data in the database. Although the work was focused on COBOL, the idea of a host-language independent database was starting to emerge, prompted by IBM's advocacy of PL/I as a COBOL replacement.

In 1971, largely in response to the need for programming language independence, the work was reorganized: development of the Data Description Language was continued by the Data Description Language Committee, while the COBOL DML was taken over by the COBOL language committee. With hindsight, this split had unfortunate consequences. The two groups never quite managed to synchronize their specifications, leaving vendors to patch up the differences. The inevitable consequence was a lack of interoperability among implementations.

A number of vendors implemented database products conforming (roughly) to the DBTG specifications: the most well-known implementations were Honeywell's Integrated Data Store (IDS/2), Cullinet's Integrated Database Management System IDMS, Univac's DMS-1100, and Digital Equipment Corporation's DBMS32. Cullinet, originally known as Cullinane Database Systems, obtained the technology from B.F. Goodrich. Cullinet was eventually sold to Computer Associates, which as of 2007 still sells and supports a version of IDMS.

ANSI and ISO adopted the Codasyl database specifications under the name Network Database Language (NDL), with work taking place within the same working group (X3H2) as SQL standardization. An ISO standard for NDL was ratified as ISO 8907:1987^[2], but it never had any practical effect on implementations, and was formally withdrawn in 1998^[3].

Some of the CODASYL committees continue their work today, but CODASYL itself no longer exists. The records of CODASYL were donated to the Charles Babbage Institute and a catalog may be found at their website.

Interest in CODASYL gradually faded due to growing interest in relational databases beginning in the early 1980's.

See also

• Navigational database
• T. William Olle

References

Further reading

• The Codasyl Approach to Data Base Management. T. William Olle. Wiley, 1978. ISBN 0-471-99579-7.
• The Codasyl Model. J. S. Knowles and D. M. R. Bell, in Databases - Role and Structure, ed. P. M. Stocker, P. M. D. Gray, and M. P. Atkinson, CUP, 1984. ISBN 0-521-25430-2

External links

• Conference on Data Systems Languages Records, 1959-1987 {CODASYL}. Charles Babbage Institute. University of Minnesota, Minneapolis. Collection contains minutes, correspondence, reports, documentation for Nice Standard Control Language (NICOLA), the Journal of Development, and other publications from several CODASYL committees and task groups.
• Conference on Data Systems Languages {CODASYL} Survey Report, 1968. "The CODASYL Systems Committee 1968 Survey of Data Base Systems" lists several dozen database systems surveyed by the group that created the CODASYL database standard.
• American National Standards Institute. X3H2 records, 1978-1995. Charles Babbage Institute. University of Minnesota, Minneapolis. Collection documents the H2 committee’s development of the NDL and SQL standards as follow-on from CODASYL.