Object algebra and views for multi-objectbases

This paper addresses the problem of defining views that span several objectbases. Views are expressed in terms of an object algebra. We are interested in the degrees of coupling and in the degrees of integrity maintained through multi-objectbase views. A key issue is the problem of global object identity. Each local system has its private object identifiers (OIDs) to represent objects. Globally, however, we need other mechanisms to uniquely refer to objects. We propose a technique that is based on the definition of (updatable) views: Queries to other objectbases are used as a referencing mechanism. The mechanism is useful as a formal basis for (partial or complete) schema integration in multi-objectbase systems