Hierarchical derivation of Petri net models of composite schedules for manufacturing cells

Composite schedules for manufacturing cells (or robotic cells) are schedules in which several parts enter and leave the cell in each cycle (although the parts which leave the cell are not necessarily the same as the ones that enter the cell). It appears that composite schedules can easily be transformed into timed Petri net models in which the timed transitions represent the actions (including the durations) of the robot and the machines of the cell. Moreover such models can be derived using stepwise refinements of net models. Hierarchical modeling is obtained by systematic application of the refinement steps