Simulating global software evolution processes by combining simple models: an initial study
Paul Wernick, Tracy Hall · Software Process Improvement and Practice · 2002
Abstract A number of studies of the long‐term evolution of commercial software products over many releases have established a consistent pattern for growth in the size of the systems examined. This shows a trend towards a progressive slowdown in growth over time. The work described here forms the first step in developing a simulation of the combined effects of the causes of this trend. A number of simple system dynamics simulations, each capturing the causal structure and behaviour of one of a number of causes believed to contribute to the observed behaviour, and its calibration to follow the observed trend, is presented. These models are then combined into a single simulation model reflecting the effect in combination of these causes. Possible causes considered here are: the reduction over time in both the conceptual space which can be searched for new uses of a system and the design spaces constraining developers' ability to modify their systems, the effects of the degradation of the structure of a software system as is it is evolved in unanticipated directions, and the reducing coverage of developers' knowledge of the structure of the system. The combined model incorporates all of these causal mechanisms and introduces a relative weighting for each. The long‐term aim of this work is to produce a simulation embodying those possible causes which are found to be supported by actual evidence. Calibration of this model to reflect the relative importance of each cause in a real‐world situation should then enable it to reproduce the actual software system size trend, so assisting in identifying those causes which affect most significantly the growth trend of that system. Copyright © 2003 John Wiley & Sons, Ltd.