This book constitutes the refereed proceedings of the Second International Workshop on Rules and Rule Markup Languages for the Semantic Web, RuleML 2003, held in Sanibel Island, Florida, USA in October 2003 in conjunction with ISWC 2003. Rules and rule markup languages will play an important role for the success of the semantic Web. Rules will act as a means to draw inferences, to express constraints, to specify policies for reaching to events, to transform data, etc. Rule markup languages will allow to enrich Web ontologies by adding definitions of derived concepts, to publish rules on the Web, to exchange rules between different systems, etc. The nine revised full papers presented together with two invited papers were carefully reviewed and selected for presentation. All current issues on rules and rule markup languages for the semantic Web are addressed.