Query Modification in Object-oriented Database Federation

We discuss the modification of queries against an integrated view in a federation of object-oriented databases. We present a generalisation of existing algorithms for simple global query processing that works for arbitrarily defined integration classes. We then extend this algorithm to deal with object-oriented features such as queries involving path expressions and nesting. We show how properties of the OO-style of modelling relationships through object references can be exploited to reduce the number of subqueries necessary to evaluate such querie

Integrity Control Based on Object Behaviour

As databases are meant to describe real-world situations, the ultimate goal of database integrity control is to ensure that at any moment, the database state corresponds exactly to the current state of the real world. Currently, the specification of database integrity is usually based on the formulation of integrity constraints -- conditions on database states describing those states considered to correspond to possible real-world states. We observe that constraint-based integrity control can be successful only if considerable knowledge of the real world is available. For many complex application domains, however, this is not the case. We describe how in these contexts, integrity can be defined by means of a set of trusted basic facts, and procedures which are believed to generate reliable new facts. We then show that the object-oriented data model is well-suited to support this alternative database integrity paradigm. We use an example from the oil industry to illustrate our ideas. A ..