People-driven mobile collaborative processes are increasingly mediated by technology due to the ubiquity, efficiency and flexibility that modern groupware systems provide their users. However, identifying groupware requirements to be considered in their development is a challenging task, since the processes being supported by them do not have a clear workflow coordinating the activities performed by the participants. Thus, software developers must usually guess these requirements based on their own experience, and so the elicitation process becomes a creative activity instead of an engineering process. Trying to reduce this uncertainty about groupware requirements identification, and thus helping developers improve their capability to predict the suitability of a collaborative system, this paper presents a visual notation to represent user interaction scenarios through models. These models are processed to automatically determine a set of potentially required groupware services. Thus, this proposal reduces the uncertainty about the groupware requirements to be considered in the development of a system supporting a particular people-driven mobile collaborative process. The usability and usefulness of the visual notation and the method to derive the groupware requirements are illustrated with a running example, and also through its application to a case study. The results are encouraging and consistent, allowing us to augur potential adoption in research and industrial settings.