Business process modelling languages enable the depiction of the processes of an organisation by exploiting graphical symbols to denote the key elements to be represented. Despite the variety of approaches, graphical symbols, and (in)formal interpretations associated to the different languages, a fundamental component of every business process modelling language is the representation of the way activities are related by means of control arcs and gateways. While multiple kinds of relationships may hold among such activities, mainstream business process modelling languages seem actually only interested in modelling a single (very important) kind of relationship, namely the activity execution order within the control flow. In this paper we investigate the role of another kind of fundamental relationship between activities, namely ontological dependence, in the context of business process modelling. In particular, we introduce three forms of generic ontological dependence, namely historical dependence, causal dependence, and goal-based co-occurrence. We illustrate different forms in which they can occur, we introduce a language to express them and we discuss their usefulness in two concrete use cases.
