This thesis presents a study of the epistemological and cognitive assumptions which currently underlie knowledge acquisition for legal ontology engineering. The hypothesis is that such assumptions might have a qualitative effect on the final ontologicalterminological resources and therefore on the performance of the systems which use them.The first part of the thesis presents the state of the art in legal ontology engineering (the computational concept of ontology, a review of available legal ontologies and modelling methodologies). The second part of the thesis shows that currently knowledge acquisition in legal ontology learning is limited to very concrete legal genres, namely, legislation, case law and legal doctrine. The third part presents a case study in which two different legal genres are used for building a consumer law ontology: a traditional legal genre, Italian consumer regulation, and a Web 2.0 genre, namely an online corpus of citizens’ queries regarding consumer justice. Results proof the impact of legal genre variation on the construction of the domain ontology. Thus main findings suggest that Web 2.0 corpora are a rich source for the construction of ontological resources, and at the same time these new types of ontological resources might be useful in e-government applications aimed at increasing online communication with citizens. The framework in which the study is conducted is the convergence between Web 3.0 and Web 2.0. This convergence implies the addition of one level of complexity to the main goal of the Semantic Web (or Web 3.0). Indeed, whereas Web 3.0 applied to the legal domain implies the automatic semantic interpretation of traditional legal sources (i.e. laws, judgements, administrative decisions), and Web 2.0 implies distributed models of production of knowledge by unknown users (i.e. blogs, blawgs, forums, social networks), the convergence of both implies the semantic processing of textual input produced by laymen in a distributed way. From the point of view of governance models this technical endeavour has a direct impact on the design of new e-government platforms for public service provision and citizen participation. The study has thus a twofold relevance: technical, as far as legal knowledge acquisition methodologies and legal ontology modelling are concerned; and socio-institutional, given the importance of semantic processing of laymen input for the design of new relational patterns between citizens and institutions.