Although the field of Artificial Intelligence and Law has matured considerably, there is still no comprehensive view on the field, its achievements, and no agenda or clear direction for research. Moreover, present approaches to the development of legal knowledge-based systems (LKBS) - such as the use of rule-based systems, case-based systems, or logics - have obtained somewhat limited theoretical and practical results. This book provides a critical overview of the field by describing present approaches and analysing their problems in detail. A new "modelling approach'' to legal knowledge engineering is proposed to address these problems and provide an agenda for research and development. This approach applies recent developments in knowledge modelling to the law domain. The book's central premise, that the development of LK BS should be centred on the elaboration of explicit models of law, is well demonstrated, it is an extremely worthwhile read for anyone interested in the theoretical foundations of AI and law and knowledge representation in particular.