''Complex sociotechnical systems'' are systems made up of numerous interacting parts, both human and non-human, operating in dynamic, ambiguous and safety critical domains. Cognitive Work Analysis (CWA) is a structured framework specifically developed for considering the development and analysis of these complex socio-technical systems. Unlike many human factors approaches, CWA does not focus on how human-system interaction should proceed (normative modelling) or how human-system interaction currently works (descriptive modelling). Instead, through a focus on constraints, it develops a model of how work can be conducted within a given work domain, without explicitly identifying specific sequences of actions (formative modelling). The framework leads the analyst to consider the environment the task takes place within, and the effect of the imposed constraints on the way work can be conducted. It provides guidance through the process of answering the questions of why the system exists, what activities can be conducted within the domain as well as how these activities can be achieved, and who can perform them. The first part of the book contains a comprehensive description of CWA, introducing it to the uninitiated. It then presents a number of applications in complex military domains to explore and develop the benefits of CWA. Unlike much of the previous literature, particular attention is placed on exploring the CWA framework in its entirety. This holistic approach focuses on the system environment, the activity that takes place within it, the strategies used to conduct this activity, the way in which the constituent parts of the system (both human and non-human) interact and the behaviour required. Each stage of this analysis identifies the constraints governing the system; it is contended that through this holistic understanding of constraints, recommendations can be made for the design of system interaction; increasing the ability of users to cope with unanticipated, unexpected situations. This book discusses the applicability of the approach in system analysis, development and evaluation. It provides process to what was previously a loosely defined framework.