The CROQUE-Model : Formalization of the Data Model and Query Language
Holger Riedel, Marc H. Scholl · KOPS (University of Konstanz) · 1996
The ODMG proposal has helped to focus the work on object-oriented databases (OODBs) onto a common object model and query language. Nevertheless there are several shortcomings of the current proposal stemming from the adaption of concepts of object-oriented programming and a lack of formalization. In this paper we present a formalization of the ODMG model and the OQL query language that is used in the CROQUE project as a basis for query optimization. An essential part is a complete, formally sound type system that allows us to reason about the types of intermediate query results and gives rise to fully orthogonal queries, including useful extensions of projections and set operations. 1 Introduction For a long time, the evolution of OODB seemed to disperse in quite different directions: there were rather distinct object-oriented database models (OODMs) either based on (nested) relational formalisms or OOPL-like notions, and hardly any consensus about the structure and formalization of q...