Activity nets: A guided tour through some recent developments

The first papers on activity nets (under the names of the CPM and PERT) appeared in 1959. Therefore, it is interesting to note that the first review by Bigelow appeared in 1962, a mere three years later! It covered the years 1959–1961, and classified contributions according to: basic principles, industrial applications, and military applications of the PERT methodology. In 1966 Lerda-Olberg provided a review covering the years 1962–1965 in which contributions were classified according to: general, theory, programming, and applications. The next landmark review is due to Adlakha and Kulkarni, which appeared in late 1989 and covers, in the main, the years 1966–1987 (with few exceptions from prior years). It concentrates on stochastic PERT networks and is ‘methodology oriented’, discussing, in sequence: pre-estimation analysis, error/bias due to assumptions, exact analysis, and Monte Carlo Sampling approaches. Mention should also be made of the books on activity nets, since they constitute important landmark summaries of the state-of-the-art at the time of their writing (which is typically some 12 to 18 months before their appearance), arranged chronologically: Battersby in 1970, Whitehouse in 1973, Elmaghraby in 1977, Kerzner in 1979, Moder, Phillips and Davis in 1983, and Słowinski and Weglarz in 1989. This guided tour is more ‘problem oriented’ – in the sense of addressing the issues that are of concern to managers of large scale projects, and hence are, or should be, also of concern to scholars and researchers in the field. Consequently, this tour is ‘applied’ in perspective because of that orientation, though we hasten to emphasize that we discuss contributions to theory and methodology everywhere. Still, our classification stems from the point of view of issues and concerns rather than theoretical results or methodology. We shall confine ourselves, on the whole, to developments that occurred in the years 1987–94 with some forays into earlier contributions to maintain continuity of presentation.