The Experience Factory: Packaging Software Experience

Since software deals with man-made artifacts, we need to view software development as an experimental science and build models of the artifacts and the processes by which they are manufactured. To do this we need to isolate and categorize the components of the discipline, define notations for representing these components, and specify the interrelationships among these components as they are manipulated. The components of the discipline consist of various processes (e.g. We need to build descriptive models of the discipline components to better understand (1) the nature of the processes and products and their various characteristics, (2) the variations among them, (3) the weaknesses and strengths of both, and (4) mechanisms to predict and control them. Models exist for some components, for example there are several mathematical models of programs and modules, there are parametrized cost models that attempt to predict the cost of a project based upon past experience, there are informal descriptions of the life cycle process. However many more models are needed and those models that do exist need to be more formally defined and further analyzed and integrated to provide a deeper understanding of the components and their interactions. Based upon analysis of these descriptive models, we need to build prescriptive models that improve both products and and the processes for creating them relative to a variety of qualities, provide feedback for project control, and allow the packaging of successful experience. Because the overall solutions are both technical and managerial, model building requires the support of a variety of disciplines both within and outside the discipline. The overall approach requires an approach, similar to the scientific method, that allows us to experiment, measure, learn, build better models, and reuse past experiences. For the past 15 years, we have been applying such an approach, the Quality Improvement Paradigm,in the Software Engineering Laboratory (SEL) at NASA/GSFC. It adapts the scientific method to software development. As stated in the first chapter, the basic steps involve: Planning: an iterative process involving characterizing the current project and its environment, setting the quantifiable goals for successful project performance and improvement, and choosing the appropriate process model and supporting methods and tools for this project. Execution: a closed-loop project cycle which involves executing the processes, constructing the products, collecting and validating the prescribed data ,and analyzing it in real-time to pride feedback for corrective action on the current project.