Approach to a Theory of Software Process and Software

Three FEAST workshops were held at Imperial College during 1994/5 [fea94/5] to explore the FEAST hypothesis, itself formulated in 1993 [leh94]. The FEAST/1 project (1996-8) [leh95] funded by EPSRC followed and led, in turn, to FEAST/2 (1999-2001) [leh98]. Many of the results of these studies have been published over the past few years. They may be found on the FEAST web site at As part of their investigation, the projects obtained evolution data on a number of systems from the formal collaborators, ICL, Logica, Matra-BAE and MoD-DERA and BT (FEAST/2). Similar data was also received from Lucent Technologies through the good offices of Professor Dewayne Perry, who, together with Professor Wlad Turski, are EPSRC Senior Visiting Fellows to the projects. The release-based systems studied had each been evolved in a sequence of from 15 to 30 releases over some eight to twenty years. Models and analysis of the data and interpretation of the results revealed striking similarities in the evolutionary patterns and long term trends of these systems. Moreover the newly observed patterns and trends were strikingly similar to those of OS/360 and several other systems studied in the 70s [leh98b]. This despite the fact that the systems studied were developed and evolved by different organisations, addressed different application areas and implemented distinct architectures using different languages. Moreover the systems studied differed in their size by up to two orders of magnitude and in the number of persons involved in their evolution by even more. Since the day to day control of the evolution process was in the hands of humans, differences between the several systems in their short term evolutionary behaviour were to be expected. The similarity of their long term behaviour, however, would have come as a surprise had not the 70s and 80 interpretation of the initial OS/360 observations, their subsequent phenomenological interpretation and the encapsulation of the observations and their interpretations in a set of laws of software evolution [leh74,78,80,96] prepared the investigators for such commonality. Thus the FEAST/1 results were seen as further support for six of the eight laws and supported many of the other conclusions that had been reached. The new evidence did, however, suggest some minor changes to the wording of the laws [leh98b]. As the laws developed over a period of fifteen years no thought was given to any relationship between them. The observed behaviour was regarded as characterising industrial team …