We describe how Event-Condition-Action (ECA) rules can be combined with event algebras like SNOOP for specification of the event part, and process algebras like CCS for specification of the action part to obtain a powerful, declarative formalism that also covers intuitively procedural tasks in an appropriate way. Since these formalisms have a concise formal semantics, verification and other kinds of reasoning about such specifications are possible. Using a rule markup with cleanly distinguished rule components allows for such a compositional approach. The approach is currently under implementation in the MARS (Modular Active Rules for the Semantic Web) Framework.

This paper is an extended version of International Conference on Rules and Rule Markup Languages for the Semantic Web (RuleML) (2006).