Infrastructure for Web Explanations The Semantic Web lacks support for explaining knowledge provenance. When web applications return answers, many users do not know what information sources were used, when they were updated, how reliable the source was, or what information was looked up versus derived. The Semantic Web also lacks support for explaining reasoning paths used to derive answers. The Inference Web (IW) aims to take opaque query answers and make the answers more transparent by providing explanations. The explanations include information concerning where answers came from and how they were derived (or retrieved). In this paper we describe an infrastructure for IW explanations. The infrastructure includes: an extensible web-based registry containing details on information sources, reasoners, languages, and rewrite rules; a portable proof specification; and a proof and explanation browser. Source information in the IW registry is used to convey knowledge provenance. Representation and reasoning language axioms and rewrite rules in the IW registry are used to support proofs, proof combination, and semantic web agent interoperability. The IW browser is used to support navigation and presentations of proofs and their explanations. The Inference Web is in use by two Semantic Web agents using an embedded reasoning engine fully registered in the IW. Additional reasoning engine registration is underway in order to help provide input for evaluation of the adequacy, breadth, and scalability of our approach. http://www.ksl.stanford.edu/people/pp/papers/McGuinness_ISWC_2003.pdf http://www.ksl.stanford.edu/software/IW/newregistry/TM/IW-TEAM.daml#IW-TEAM Tue Sep 23 14:46:32 PDT 2003