Maintenance and Testing Effort Modelled by Linear and Non Linear Dynamic Systems

The dynamic evolution of ecological systems in which predators and prey compete for surviving has been investigated by applying suitable mathematical models. Dynamic systems theory provides a useful way to model interspecies competition and thus the evolution of predators and prey populations. This kind of mathematical framework has been shown to be well suited to describe evolution of economical systems as well, where instead of predators and prey there are consumers and resources Maintenance and testing activities absorb the most relevant part of total lifecycle cost of software. Such economic relevance strongly suggests to investigate the maintenance and testing processes in order to find new models allowing software engineers to better estimate, plan and manage costs and activities. In this paper we show how dynamic systems theory could be usefully applied to the maintenance and testing context, namely to model the dynamic evolution of the effort. When programmers start trying to recognize and correct code defects, while the numbers of residual defects decreases, the effort spent to find out any new defect has an initial increase, followed by a decline, in a similar way as prey and predators populations do. The feasibility of this approach is supported by the experimental data about two real world software project