This book constitutes the refereed proceedings of the Second International Conference on Web Reasoning and Rule Systems, RR 2008, held in Karlsruhe, Germany in October/November 2008. The 12 revised full papers, 4 revised short papers presented together with 5 poster papers were carefully reviewed and selected from over 35 submissions. The papers address all current topics in Web reasoning and rule systems such as acquisition of rules and ontologies by knowledge extraction, design and analysis of reasoning languages, implemented tools and systems, standardization, ontology usability, ontology languages and their relationships, rules and ontologies, reasoning with uncertainty, reasoning with constraints, rule languages and systems, semantic Web services modeling and applications.