Abstract: Here described are the design of event condition action（ECA） rule to support the active capability in OODBMS and its implementation in C++ environment. It supports temporal,explicit and composite events in addition to the traditional database events.A set of event operators are introduced for building composite events. A concept of event interfaces is also introduced. These event interfaces are used to describe the events spanning objects, possibly from different classes. They are also used to detect and signal the occurrence of events. The concept of reactive and notifiable objects is proposed to unify events and rules into objects. A subscription mechanism between rules and objects is also introduced to monitor the objects selectively.