Semantic Web Search and Inductive Reasoning Claudia d’Amato 1 , Nicola Fanizzi 1 , Bettina Fazzinga 2 , Georg Gottlob 3,4 , and Thomas Lukasiewicz 3 1 Dipartimento di Informatica, Universit` a degli Studi di Bari, Italy {claudia.damato,fanizzi}@di.uniba.it 2 Dipartimento di Elettronica, Informatica e Sistemistica, Universit` a della Calabria, Italy bfazzinga@deis.unical.it 3 Department of Computer Science, University of Oxford, UK firstname.lastname@cs.ox.ac.uk 4 Oxford-Man Institute of Quantitative Finance, University of Oxford, UK Abstract. Extensive research activities are recently directed towards the Seman- tic Web as a future form of the Web. Consequently, Web search as the key tech- nology of the Web is evolving towards some novel form of Semantic Web search. A very promising recent such approach is based on combining standard Web pages and search queries with ontological background knowledge, and using stan- dard Web search engines as the main inference motor of Semantic Web search. In this paper, we further enhance this approach to Semantic Web search by the use of inductive reasoning techniques. This adds especially the important ability to handle inconsistencies, noise, and incompleteness, which are all very likely to occur in distributed and heterogeneous environments, such as the Web. We report on a prototype implementation of the new approach and experimental results. 1 Introduction Web search [6] as the key technology of the Web is about to change radically with the development of the Semantic Web [3]. As a consequence, the elaboration of a new search technology for the Semantic Web, called Semantic Web search [18], is currently an extremely hot topic, both in Web-related companies and in academic research. In particular, there is a fast growing number of commercial and academic Semantic Web search engines. The research can be roughly divided into two main directions. The first (most common) one is to develop a new form of search for searching the pieces of data and knowledge that are encoded in the new representation formalisms of the Semantic Web (e.g., [18]), while the second (less explored) direction is to use the data and knowledge of the Semantic Web to add some semantics to Web search (e.g., [27]). A very promising recent representative of the second direction to Semantic Web search has been presented in [22]. The approach is based on (i) using ontological (unions of) conjunctive queries (which may contain negated subqueries) as Semantic Web search queries, (ii) combining standard Web pages and search queries with on- tological background knowledge, (iii) using the power of Semantic Web formalisms and technologies, and (iv) using standard Web search engines as the main inference motor of Semantic Web search. It consists of an offline ontology compilation step, based on deductive reasoning techniques, and an online query processing step.