Monitoring Database Objects

A method is described for actively interfacing an Object-Oriented Database Management System (OODBMS) to application pre grams. The method, called a database monitor, observes how values of derived or stored attributes of database objects change over time. Whenever such a value change is observed, the OODBMS invokes tracking procedures within running application programs. The OODBMS associates tracking procedures and the object attributes they monitor, and it invokes appropriate tracking procedures when data changes. Use is made of atomic transactions in the OODBMS. The applicability of monitors is localized both in time and space, so that only a minimal amount of data is monitored during as short a time as possible. Such localization reduces the frequency of tracking procedure invocation, makes it easy to add and remove monitors dynamically, and permits efficient implementation. To demonstrate these ideas, an implementation is described for the Iris OODBMS [lo]. The implementation uses a technique of partial view materialization for efficient implementation.