Operational approaches are based on the direct specification of the state machine, which defines the temporal scenario of the document (see Figure 1).

Constraint-based approaches are based on constraint programming and are characterized by a formatting phase that computes starting times and durations, as required by the scenario. This formatting phase can be seen as a compilation of a declarative specification into an operational structure, which can be interpreted by the presentation phase. Thus, the author specifies what scenario he needs without involvement of how to get the result in terms of operational actions, in a declarative way.