A model of queries for object-oriented databases

TLDR

Object‑oriented databases lack a comprehensive query model, despite consensus on the data model and limited support in operational systems. The paper proposes a comprehensive query model that aligns with object‑oriented concepts. The model incorporates class‑hierarchy and nested‑object semantics, making it richer than relational or nested relational query models. A substantial portion of the model has been implemented in a query language supported by the ORION database system.

Abstract

One major source of confusion, and consequent c&icisms, about object-oriented databases has been the lack of a comprehensive model of queries. Although there is a reasonable degree of agreement about an object-oriented data model, few operational systems support a query model for object-oriented databases. In this paper, we present a rather comprehensive query model which is consistent with object-oriented concepts embodied in the object-oriented data model. The model takes into account the semantics of the class hierarchy and nested objects, and as such is inherently richer than the relational or nested relational model of queries. A significant subset of the model has been cast into a query language which is supported in the ORION object-oriented database system.