Automatic Design of the Internal Schema for a CODASYL Database System

This paper describes the concepts and implementation of a design aid for the internal schema of an existing CODASYL-like database system. It allows for tailoring the storage structure level to a given logical schema and a specified workload. According to the 1978 CODASYL report, our DBMS provides two levels of schema declaration, the DDL-level for logical schema description and a DSDL-like level for specifying the storage structures to implement the objects of the logical schema. The repertoire of storage structures supported by our system is a good internal schema are basically heuristic. This approaach is justified by weighing its advantages and shortcomings against those of analytic models and simulation. Finally, some preliminary user experiences with a pilot version are related.