Asynchronous monitoring of events for distributed cooperative environments

Most of the work in active databases (event specification and detection) has concentrated on centralized environments. In other words, ECA rules are accepted and managed by active DBMSs within the same address space. However, cooperative problem solving environments are inherently distributed and heterogeneous; hence there is a need for supporting ECA (Event-Condition-Action) rules in a distributed setting. The paper analyzes the design and implementation considerations of an asynchronous event detector termed GEM (Global Event Manager) that can detect and communicate events along with their parameters in a distributed environment. The paper presents extension to the Snoop event specification language to accommodate distributed event specification and develops an architecture and its implementation in the context of the Sentinel active OODBMS. A distributed plan monitoring application and a flexible manufacturing application have been developed using the functionality and the system described in the paper.