Includes supplementary material: sn.pub/extras

Invited Talks.- Semantic Web Rules: Covering the Use Cases.- Combining Rule and Ontology Reasoners for the Semantic Web.- Regular Papers.- A System for Nonmonotonic Rules on the Web.- Rule Learning for Feature Values Extraction from HTML Product Information Sheets.- A Defeasible Logic Reasoner for the Semantic Web.- R-DEVICE: A Deductive RDF Rule Language.- Well-Founded Semantics for Description Logic Programs in the Semantic Web.- Defeasible Description Logics.- Semantic Web Reasoning with Conceptual Logic Programs.- Bossam: An Extended Rule Engine for OWL Inferencing.- Extending SWRL to Express Fully-Quantified Constraints.- An Extension to OWL with General Rules.- Combining Description Logic and Defeasible Logic for the Semantic Web.- Short Tool Presentations.- Rewrite Rules as Service Integrators.- SweetProlog: A System to Integrate Ontologies and Rules.- SWRLp: An XML-Based SWRL Presentation Syntax.- XET as a Rule Language for Consistency Maintenance in UML.- A System for Automated Agent Negotiation with Defeasible Logic-Based Strategies - Preliminary Report.

The Semantic Web is a worldwide endeavor to advance the Web by enriching its content with semantic metainformation that can be processed by inferen- enabled Web applications. Taxonomies and rules, along with their automated reasoning techniques, are the main components of Semantic Web ontologies. Rule systems are considered to be a major area in the further development of the Semantic Web. On one hand, rules can specify declarative knowledge in ontology languages, expressing constraints or transformations, either in conju- tionwith,orasanalternativeto,descriptionlogics.Ontheotherhand,rulescan specify behavioral knowledge, enforcing policies or reacting to events/changes. Finally, rule markup languages such as RuleML allow us to publish rules on the Web, to process rules in general XML environments as well as special rule engines, to exchange rules between di?erent applications and tools via XSLT translators, as well as to embed rules into other XML content and vice versa. This workshop was dedicated to all aspects of rules and rule markup l- guages for the Semantic Web. RuleML 2004 was the third in a series of wo- shops that was initiated with the International Semantic Web Conference. The previous workshops were held on Sardinia, Italy (2002), and on Sanibel Island, USA (2003). Thisyearwehad25submissions,ofwhich11wereacceptedasregularpapers and another ?ve as short papers describing tools. Wearegratefultoourtwoinvitedspeakers,MikeDeanfromBBNandChr- tine Golbreich from the University of Rennes. Our thanks also go to all subm- ters and reviewers without whom the workshop and these proceedings could not have succeeded.