Activity models are described through HOPEX functional processes. These models are composed of participants (roles involved in the process) and functional activities (tasks performed by participants). Functional processes describe scenarios of operational node structures. The participants can therefore be assigned by either operational nodes or operational components (the contextualized embodiment of an operation node). Functional activities can rely on sub-processes (called functional processes).

Each functional activity can be sequenced in a functional process via a Sequence Flow.

Functional activities may exchange information through message flows. Information can also be retrieved from/created in data objects. Data objects attached to sequence flows are actually shortcuts to the source in the data object while the target retrieves the information to perform the activity. Data objects can be defined with states.