BACKGROUND AND DEFINITION OF CONCEPTS
In this chapter, we lay out the general foundation for case study research in software engineering. We characterize the case study strategy and compare it with other empirical research strategies, primarily survey, experiment, and action research. Aspects of empirical research strategies are elaborated, for example, their primary purpose, whether they have a fixed or flexible design, whether data are quantitative or qualitative, and the roles which triangulation and replication play. We discuss, on the basis of different sources within and outside software engineering, what constitutes an exemplary case study and summarize criteria or good case study research. We set out a scheme to help decide when case study is a feasible research strategy, and we define a general research process for case studies, which is used throughout the book.
2.2 RESEARCH STRATEGIES
Let us start with three different general definitions of the term case study, one by Robson , one by Yin , both in the social science field, and one definition by Benbasat et al.  in the information systems field.
Robson. Case study is a strategy for doing research that involves an empirical investigation of a particular contemporary phenomenon within its context using multiple sources of evidence.
Yin. Case study is an empirical inquiry that investigates a contemporary phenomenon within its real-life context, especially when the boundaries between ...