Requirements and comparison of view mechanisms for object-oriented databases

摘要

Views in the relational data model have proved indispensable in order to provide logical data independence through external schemas that can be customized to meet the needs of individual users. Since object-oriented database systems (OODBs) are expected to provide at least the functionality of today's relational systems, view mechanisms for OODBs have recently received attention. Due to the higher expressive power of object-oriented data models when compared with the relational one, different interpretations of an object-oriented view concept coexist. This paper states the requirements and discusses the features of object-oriented view mechanisms, in order to review and systematically compare representative proposals from the literature. Individual issues concerning object-oriented views, such as view definition, typing, object-preservation versus creation, view updates, and positioning of view classes into a class/type hierarchy are addressed. The paper aims to provide insight into the state-of-the-art of object-oriented views, to discuss some trade-offs in supporting advanced features, to draw some general conclusions regarding object-oriented data models, and to indicate issues for further research.