Abstract. The Web of today can be seen as an active and heterogeneous infrastructure of autonomous systems, where reactivity, evolution and propagation of information and changes play a central role. In the same way as the main driving force for XML and the Semantic Web idea was the heterogeneity of the underlying data, the heterogeneity of concepts for expressing behavior calls for an appropriate handling on the semantic level. We present an ontology-based approach for specifying behavior in the Semantic Web by Event-Condition-Action (ECA) rules that models rules as well as their event, condition, and action components, and languages as resources. The necessary information about semantics and suitable processors is then associated with the language resources. The approach makes use of the data integration facilities by URIs that allow for a seamless integration of information and services physically located at different places. Additionally, that point of view allows for sharing and ...