This paper focuses on situations where documents serve to coordinate a distributed Community of Action engaged in a common goal-directed activity. In such contexts, a document appears as a set of fragments contributed by various authors. Furthermore, it is possible to analyse the traces of collective activity left in documents. This analysis may serve several purposes. Among other things, it may be used to understand the evolution of the cognitive and social dynamics of the community. After justifying the choice of the DofA (Documents for Action) conceptual framework, we elaborate a UML-based model of DofA. We use this model as a structure for conceptually representing traces of mediated collective activities. We pursue with the issue of dependency analysis and measurement, which leads us to propose specific dependencies in the context of DofA. We illustrate the early steps of an application to a scenario of collective writing. Finally, we discuss further research directions suggested by our approach, which analyses and measures dependencies from traces of mediated collective activity.