This paper retrospectively analyzes the progress of event-based capability and their applicability in various domains. Although research on event-based approaches started in a humble manner with the intention of introducing triggers in database management systems for monitoring application state and to automate applications by reducing/eliminating user intervention, currently it has become a force to reckon with as it nds use in many diverse domains. This is primarily due to the fact that a large number of real-world applications are indeed event-driven and hence the paradigm is apposite. In this paper, we brie y overview the development of the ECA (or event-condition-action) paradigm. We brie y discuss the evolution of the ECA paradigm (or active capability) in relational and Object-oriented systems. We then describe several diverse applications where the ECA paradigm has been used effectively. The applications range from customized monitoring of web pages to speci cation and enforce...