ELECTRONIC WORKSHOPS IN COMPUTING Series edited by Professor C.J. van Rijsbergen D Duke, University of York, UK and A S Evans, University of Bradford, UK (Eds) BCS-FACS Northern Formal Methods Workshop Proceedings of the BCS-FACS Northern Formal Methods Workshop, Ilkley, UK. 23-24 September 1996 CASE-Based Rigorous Object-Oriented Modeling J.-M. Bruel, R.B. France, M.M. Larrondo-Petrie, B. Chintapally and G.K. Raghavan Published in collaboration with the British Computer Society ©Copyright in this paper belongs to the author(s)