Bridging the gap between individual mental models of stakeholders and organizational or software developers requires a diagrammatic acquisition and representation scheme that captures information provided by stakeholders in an accurate way for all involved parties. In this paper we reflect an action research approach for deriving such a scheme, and revisit existing approaches in the light of our developments. Since human-centered diagrammatic representation schemes need to ensure the intelligibility of process knowledge, they have to provide dedicated modeling elements, such as contextual information types.