Approaches to legal ontologies constitutes a collective reflection on the foundations of legal ontology engineering, by exploring current methodologies and theoretical approaches to defining legal ontologies, their divergences and complementarity and the challenges still to be faced. It gathers contributions from leading experts regarding their theoretical commitments and methodological approaches derived from a long experience in the area and presents a mature reflection on achievements and current shortcomings. The various authors reconstruct their concrete methodological frameworks by retrieving the more or less explicit theoretical choices that have guided their work on legal ontology engineering over the last years. This results in the presentation of apparently opposed but in fact complementary rationales for ontology building in the legal domain (legal-theoretical, sociolegal, philosophical, among others) that address the various dimensions of legal knowledge and its conceptual modelling. The book provides the reader with a unique source regarding the current theoretical landscape in legal ontology engineering as well as on foreseeable future trends for the definition of conceptual structures to enhance the automatic processing and retrieval of legal information in the Semantic Web framework. It will thus interest researchers in the domains of the SW, legal informatics, Artificial Intelligence and law, legal theory and legal philosophy, as well as developers of e-government applications based on the intelligent management of legal or public information to provide both back-office and front-office support.