C. Robert Carlson

A Comparison of the Relational and CODASYL Approaches to Data-Base Management

Data definition, manipulation, protection, and independence, and System performance are important factors when studying and evaluating data-base management systems to be used in shared data-base environments. The relational and CODASYL Data Base Task Group approaches, which have been widely discussed and debated, are compared and contrasted from these points of view. The paper concludes with the observation that since data-base management systems are to serve the needs of widely diverse communities of users, no single approach to data-base management seems either desirable or likely to emerge as dominant in the near future.

A generalized access path model and its application to a relational data base system

An Access Path Producing LanguagE (APPLE) has been developed which permits users to formulate completely non-procedural queries expressed solely in terms of attribute names. The responsibility for programming or specifying the access path by which a query is resolved has thus been shifted from the user to the system. Examples are presented which illustrate the procedures by which the system determines an access path. The problems to be found in this approach are also described, and techniques required to solve these problems are presented.

Self-Assessment Procedure V: Database Systems.

This is the fifth ACM self-ass~ssment procedure. The earlier ones appeared in Communications in May 1976, May 1977, September 1977, and February 1978. This procedure deals with databases: general concepts, relational, network, and hierarchical approaches, physical design, and security/integrity. Reader response to the earlier procedures showed that the basic educational aims of self-assessment can be achieved with small procedures that do not satisfy the requirements usually applied to testing, or certification. Consequently, this procedure is short and is neither exhaustive nor balanced in its coverage. It merely provides a path to some self-assessment. The next few paragraphs abbreviate the introduction and instructions given with the earlier procedures.