Deductive queries in ODMG databases: the DOQL approach

The Deductive Object Query Language (DOQL) is a rule-based query language designed to provide recursion, aggregates, grouping and virtual collections in the context of an ODMG compliant object database system. This paper provides a description of the constructs supported by DOQL and the algebraic operational semantics induced by DOQL's query translation approach to implementation. The translation consists of a logical rewriting step used to normalise DOQL expressions into molecular forms, and a mapping step that transforms the canonical molecular form into algebraic expressions. The paper thus not only describes a deductive language for use with ODMG databases, but indicates how this language can be implemented using conventional query processing techniques.