On what exactly goes on when software is developed step-by-step, II: The sequel

At the workshop in honour of his 65th birthday, Wlad Turski reprised his professional life and, unusually for him, ended on a pessimistic note. He seemed to think that his and others' efforts to introduce systematic, mathematically based engineering methods for software had been a failure. The purpose of this article is to rehearse the contents of our 1984 ICSE paper [Maibaum, Turski, in: Proc. 7th Internat. Conf. on Software Engineering, 1984] about the formal construction of software and then review what has happened in the twenty or so intervening years. The article concludes by pointing to the half full glass of formally based achievements in software engineering, in contrast to the largely empty glasses of earlier times.