Increasingly we need to be able to coordinate the interactions between real human actors in software—humans are, of course, a key participant in almost every software system.
Human workflow involves coordinating business processes that involve people. Within human workflow these people communicate with various systems and other people in a business process implemented in software using a workflow model. Using a model, we can take pre-built units of behavior and define a workflow that coordinates them.
The key to human workflow is that those units of behavior represent not only system performed actions, but also actions and decisions undertaken by human actors.