Goel Kahen

System dynamics modelling of software evolution processes for policy investigation: Approach and example

Abstract This paper describes one of the latest in a series of system dynamics models developed during the Feedback, Evolution And Software Technology (FEAST) investigation into software evolution processes. The intention of early models was to simulate real-world processes in order to increase understanding of such processes. The work resulted in a number of lessons learnt, in particular, with regard to the application of system dynamics to the simulation of key attributes of long-term software evolution. The work reported here combines elements of previous work and extends them by describing an approach to investigate the consequences on long-term evolution, of decisions made by the managers of these processes. The approach is illustrated by discussion of the impact of complexity control activity. This model of the impact on product and global process attributes of decisions regarding the fraction of work applied to progressive and to anti-regressive activities such as complexity control, for instance, exemplifies the results of the FEAST investigation.

The FEAST Approach to Quantitative Process Modelling of Software Evolution Processes

This paper argues that quantitative process models can play an important role in seeking sustained improvement of E-type software evolution processes and summarises some of the experiences gained in the FEAST projects to date. Modelling guidelines are provided.

Simulation Process Modelling for Managing Software Evolution

Software that is regularly used for real world problem solving or addressing a real world application must be continually adapted and enhanced to maintain its fitness to an ever changing real world, its applications and application domains. This adaptation and enhancement activities are termed progressive, As progressive activity is undertaken, the complexity (e.g., functional, structural) of the evolving system is likely to increase unless work, termed anti-regressive, is also undertaken in order to control and even reduce complexity. However, with progressive and anti-regressive work naturally competing for the same pool of resources, management will benefit from means to estimate the amount of work and resources to be applied to each of the two types. After providing a necessary background, this chapter describes a systems dynamics model that can serve as a basis of a tool to support decision making regarding the optimal personnel allocation over the system lifetime. The model is provided as an example of the use of process modelling in order to plan and manage long-term software evolution.

Experiences with Behavioural Process Modelling in FEAST, and Some of Its Practical Implications

The FEAST/1 (1996-1998) and FEAST/2 (1999-2001) projects have been investigating the role and impact of feedback and feedback-based system dynamics as reflected by attributes of the long term evolution of industrial software and the behaviour of the processes that evolve them. The investigation was triggered by the hypothesis that, with the possible exception of the least mature processes, software processes are multi-agent, multi-level, multi-loop feedback systems that must be managed as such to achieve sustained process improvement. This paper summarises some of the findings of the FEAST projects to date with emphasis on the process modelling methodology that were adopted and that have evolved over the duration of the two projects. Such procedures encompass both metric based black-box and white-box (system dynamics) behavioural modelling. It will also draw attention to the practical industrial application of the results obtained in the form of over thirty-five rules and guidelines for software evolution planning and management.