QAL: A query algebra of complex objects

The main motivation for the development of a query algebra of complex objects QAL is the study of the operations needed to query the structural aspects of object-oriented databases which are due to the advantages of the object-oriented database model over conventional relational and functional database models. The basic operations of the QAL query algebra evolved from relational algebras and the FQL family of functional query languages by refining their operations for the manipulation of objects. In order to support the features specific to object-oriented data models, QAL offers: (i) a set of operations which provide the means for querying conceptual schemata and (ii) an operation which provides a simple and efficient way of querying nested components of complex objects. We show through a case-study consisting of a comprehensive set of examples how these operations can be employed to express a class of queries specific to object-oriented databases. (C) 1999 Elsevier Science B.V. All rights reserved.