In the same way as the “static” Semantic Web deals with data model and language heterogeneity and semantics that lead to RDF and OWL, there is language heterogeneity and the need for a semantical account concerning Web dynamics. Thus, generic rule markup has to bridge these discrepancies, i.e., allow for composition of component languages, retaining their distinguished semantics and making them accessible e.g. for reasoning about rules. In this paper we analyze the basic concepts for a general language for evolution and reactivity in the Semantic Web. We propose an ontology based on the paradigm of Event-Condition-Action (ECA) rules including an XML markup. In this framework, different languages for events (including languages for composite events), conditions (queries and tests) and actions (including complex actions) can be composed to define high-level rules for describing behavior in the Semantic Web.