Gmd Report 38 Declarative and Procedural Object-oriented Views

In der Reihe GMD Report werden Forschungs-und Entwicklungs-ergebnisse aus der GMD zum wissenschaftlichen, nicht-kommerziellen Gebrauch veröffentlicht. Jegliche Inhaltsänderung des Dokuments sowie die entgeltliche Weitergabe sind verboten. The purpose of the GMD Report is the dissemination of research work for scientific non-commercial use. The commercial distribution of this document is prohibited, as is any modification of its content. Abstract One major approach to realise database integration is to adapt and merge the database schemas by defining views. When integrating object-oriented databases, views need to adequately support the two main concepts of object-oriented data models: object identity and methods. View objects need to be identified on the basis of the objects they have been derived from. Methods require an efficient language binding and need to be substituted by declarative query mappings where possible. In this paper we present a view system that supports both declarative and procedural integration of object-oriented databases. We have extended the object definition language ODL of ODMG-93 and use simple OQL queries for instantiating the extents of derived classes and for performing simple attribute derivations. In addition, methods can be attached to view objects in order to provide more complex view semantics. A pre-processor is employed for consistently generating the declarative and the procedural parts from a common source, and an object manager has been designed that interacts with both the query processor and the view implementation and guarantees consistent object identification and method dispatching at run-time. The presented view concept provides flexible integration semantics for object-oriented databases without sacrificing the optimisation potential. Datenbanken, erhält aber gleichzeitig die traditionellen Optimierungsmöglichkeiten.