ABSTRACT
A recurring theme in most if not all the chapters of this book is the difference between how work is being thought of either before it takes place when it is being planned or after it has taken place when the consequences are being evaluated, and how work is actually carried out where and when it happens. The two terms commonly used to describe this difference are work-as-imagined (WAI) and work-as-done (WAD). The distinction has been in use for more than half a century and is derived from the francophone use of the terms tâche (task) and activité (activity) from the 1950s onwards. The main reference in the French ergonomics literature is Leplat and Hoc (1983). At the same time Hollnagel and Woods (1983) proposed a distinction between the system task description (work-as-imagined) and the cognitive tasks (work-as-done). The distinction between WAI and WAD also played a role in the early discussions about resilience engineering, for instance in the first symposium 2004 as documented by Dekker (2006).
