Tarek K. Abdel-Hamid

Lessons learned from modeling the dynamics of software development

Software systems development has been plagued by cost overruns, late deliveries, poor reliability, and user dissatisfaction. This article presents a paradigm for the study of software project management that is grounded in the feedback systems principles of system dynamics.

The dynamics of software project staffing: a system dynamics based simulation approach

The author focuses on the dynamics of software project staffing throughout the software-development lifecycle. The research vehicle is a comprehensive system-dynamics model of the software-development process. A detailed discussion of the models structure as well as its behavior is provided. The results of a case study in which the model is used to simulate the staffing practices of an actual software project are then presented. The experiment produces some interesting insights into the policies (both explicit and implicit) for managing the human resource, and their impact on project behavior. The decision-support capability of the model to answer what-if questions is also demonstrated. In particular, the model is used to test the degree of interchangeability of men and months on the particular software project. >

The impact of goals on software project management: an experimental investigation

Over the last three decades, a significant stream of research in organizational behavior has established the importance of goals in regulating human behavior. The precise degree of association between goals and action, however, remains an empirical question since people may, for example, make errors and/or lack the ability to attain their goals. This may be particularly true in dynamically complex task environments, such as the management of software development.To date, goal setting research in the software engineering field has emphasized the development of tools to identify, structure, and measure software development goals. In contrast, there has been little micro-empirical analysis of how goals affect managerial decision behavior. The current study attempts to address this research problem. We investigated the impact of different project goals on software project planning and resource allocation decisions and, in turn, on project performance. The research question was explored through a role-playing project simulation game in which subjects played the role of software project managers. Two multi-goal structures were tested, one for cost/schedule and the other quality/schedule. The cost/schedule group opted for smaller cost adjustments and was more willing to extend the project completion time. The quality/schedule group, on the other hand, acquired a larger staff level in the later stages of the project, and allocated a higher percentage of the larger staff level to quality assurance. A cost/schedule goal led to lower cost, while a quality/schedule goal led to higher quality. These findings suggest that given specific software project goals, managers do make planning and resource allocation choices in such a way that will meet those goals. The implications of the results for project management practice and research are discussed.

Understanding the “90% syndrome in software project management: a simulation-based case study

Abstract There is ample evidence in the literature to indicate that the “90% syndrome” is pervasive in software project management. The objective of this paper is to report on a study of this important phenomenon. Our research vehicle is a System Dynamics simulation model of the software development process. Model results obtained from an analysis of a NASA software project indicate that the problem arises because of the interaction of two factors: underestimation and imprecise measurement of project progress due to poor visibility. The model is used to investigate the viability of two project strategies for “curing” the 90% syndrome problem.

Software-engineering process simulation model (SEPS)

This paper describes the Software-Engineering Process Simulation (SEPS) model developed at JPL. SEPS is a dynamic simulation model of the software project-development process. It uses the feedback principles of system dynamics to simulate the dynamic interactions among various software life-cycle development activities and management decision-making processes. The model is designed to be a planning tool to examine trade-offs of cost, schedule, and functionality, and to test the implications of different managerial policies on a projects outcome. Furthermore, SEPS will enable software managers to gain a better understanding of the dynamics of software project development and perform postmortem assessments.

Adapting, correcting, and perfecting software estimates: a maintenance metaphor

A hybrid continuous software estimation model supporting adaptive, corrective, and perfective estimation activities is described. The adaptive activity accommodates new system or user requirements or reflects new organizational realities. Corrective maintenance remedies an error detected in the software product, and perfective maintenance eliminates processing inefficiencies and enhances performance of the overall software system. An implementation using constructive cost model (Cocomo) and the system dynamics (SD) simulator is presented. Three examples are presented that demonstrate how the model can be used: before the project starts to adapt the Cocomo estimates to organizational realities, during software development to correct initial assumptions about sizing, and after project completion to perfect model estimates.<<ETX>>

The economics of software quality assurance: a simulation-based case study

Software quality assurance (QA) is a critical function in the successful development and maintenance of software systems. Because the QA activity adds significantly to the cost of developing software, the cost-effectiveness of QA has been a pressing concern to software quality managers. As of yet, though, this concern has not been adequately addressed in the literature.The objective of this article is to investigate the tradeoffs between the economic benefits and costs of QA. A comprehensive system dynamics model of the software development process was developed that serves as an experimentation vehicle for QA policy. One such experiment, involving a NASA software project, is discussed in detail. In this experiment, the level of QA expenditure was found to have a significant impact on the projects total cost. The model was also used to identify the optimal QA expenditure level and its distribution throughout the projects lifecycle.

Investigating the cost/schedule trade-off in software development

The author has studied the effects of schedule compression or stretch-out on total project cost within a much broader effort to study and predict the dynamics of the entire development process. The resulting cost/schedule tradeoffs were examined. Much of this project involved developing a comprehensive system-dynamics model. He used the model to conduct three simulation experiments. (1) He investigated the effects of different levels of schedule compression and stretch-out on total project cost in man-days and compared the results to those reported in the literature. (2) He addressed the stealthy role undersizing plays in schedule compression. (3) He investigated how different levels of managerial commitment affect the projects final cost and completion time. The results of all three experiments are presented and discussed.<<ETX>>

Exercise and Diet in Obesity Treatment: An Integrative System Dynamics Perspective

PURPOSE Demonstrate the utility of System Dynamics computer modeling to study and gain insight into the impacts of physical activity and diet on weight gain and loss. METHODS A holistic System Dynamics computer model is presented that integrates the processes of human metabolism, hormonal regulation, body composition, nutrition, and physical activity. These processes are not independent of one another, and the model captures the complex interdependencies between them in the regulation of body weight and energy metabolism. The article demonstrates how such an integrative simulation model can serve as a viable laboratory tool for controlled experimentation to investigate the impacts of physical activity and diet on body weight and composition. RESULTS In one experiment, weight loss from a moderate level of daily exercise was slightly less than the loss from dieting. Although exercise did have a favorable impact on body composition by protecting against the loss in fat-free mass (FFM), it, however, failed to blunt the drop in resting energy expenditure (REE) that accompanies diet-based weight loss. The smaller loss in FFM did indeed induce a smaller drop in REE, however, the preservation of FFM also affected a relatively larger loss in FM, which, in turn, induced a larger adaptive reduction in the metabolic rate. The two adaptations almost totally offset one another, causing minimal differences in REE. In a second experiment, exercise regimens of moderate- to high-level intensity proved counterproductive as weight-reducing strategies. However, when the diet was changed from a balanced composition to one that was highly loaded with carbohydrates, it became possible to sustain the intense exercise regimen over the experimental period and achieve a significant drop in body weight. CONCLUSION The results underscore the significant interaction effects between physical activity, diet, and body composition and demonstrate the utility of computer-based experimentation to study, gain insight into, and make predictions about their dynamics.

Modeling dynamics in agile software development

Changes in the business environment such as turbulent market forces, rapidly evolving system requirements, and advances in technology demand agility in the development of software systems. Though agile approaches have received wide attention, empirical research that evaluates their effectiveness and appropriateness is scarce. Further, research to-date has investigated individual practices in isolation rather than as an integrated system. Addressing these concerns, we develop a system dynamics simulation model that considers the complex interdependencies among the variety of practices used in agile development. The model is developed on the basis of an extensive review of the literature as well as quantitative and qualitative data collected from real projects in nine organizations. We present the structure of the model focusing on essential agile practices. The validity of the model is established based on extensive structural and behavioral validation tests. Insights gained from experimentation with the model answer important questions faced by development teams in implementing two unique practices used in agile development. The results suggest that due to refactoring, the cost of implementing changes to a system varies cyclically and increases during later phases of development. Delays in refactoring also increase costs and decrease development productivity. Also, the simulation shows that pair programming helps complete more tasks and at a lower cost. The systems dynamics model developed in this research can be used as a tool by IS organizations to understand and analyze the impacts of various agile development practices and project management strategies.