1.1 Introduction Object-oriented programming has opened a great many perspectives on the concept of software and has been hailed as part of the solution to the so-called "software crisis." It has given the possibility that software components can be constructedandreusedwithconsiderablymorecredibility.Therearenowmany case studies in which the reuse of object-oriented components has been made and analysed. Object-oriented programming relates the programming activity to that of modelling or simulation; objects are identi?ed by a correspondence with the objects found in the application area of...