Frontiers in Artificial Intelligence and Applications

Proponents of active systems have proposed Event-Condition-Action (ECA) rules, a mechanism where behavior is invoked automatically as a response to events but without user or application intervention. The environment (the programming language and the operating system) in which a system is built influences how the event detector is designed and implemented. Sentinel provided active capability to an object-oriented database environment implemented in C++. However, C++ environment had certain limitations that proved deterrent to implementing some of the features of active capability. This paper discusses the re-designing and implementation of the active subsystem in the Java environment. Main motivations behind our objective of re-designing and implementing the active subsystem in the Java environment include: i) to overcome the limitations of the C++ environment, and ii) to exploit some of the capabilities provided by the Java environment that are critical for an active system. It also provides a novel approach for supporting the creation of rules, and composite and temporal events dynamically at run time, which is inevitable for several classes of monitoring applications. This avoids recompilation and restart of the system which are inappropriate in many environments that require fine-tuning of rules on the fly. It provides a generic set of classes that are designed to handle rules dynamically. This set of generic classes is application-independent making the system a generalpurpose tool.