Object oriented technology cannot be learned from a textbook. As stressed by many authors, including  [BC89] and  [Booch94], an object oriented approach requires insight in the techniques available for object oriented modeling and preferably first-hand experience with an object oriented language. It is generally acknowledged that (both for the individual and a company) the learning required to master an object oriented approach is considerable, but necessary in order to profit from its potential benefits. To gain an understanding of what object orientation means in practice, it is worthwhile to study actual applications of object oriented programming, as for example described in  [Pinson90] and  [Harmon93]. Personally, I consider learning by example to be much more effective than learning the rules of some development method. Such methods and their accompanying tools may become effective when engaging in a large-scale project, after acquiring an initial understanding of the potential of object orientation. In particular when a (large) number of developers and programmers are involved, a common method and a shared terminology are essential to the success of a software development project, with or without an object oriented approach.