What is the difference between the PN and SDF directors?
The SDF Director executes a single actor at a time with one thread of execution. The SDF Director is very efficient and will not tax system resources with overhead. It achieves this efficiency by precalculating the schedule for actor execution. However, this efficiency requires that certain conditions be met, namely that the data consumption and production rate of each actor in an SDF workflow be constant and declared. Under a PN Director, every actor gets an execution thread and the director does not statically calculate firing schedules. The workflow is driven by data availability: tokens are created on output ports whenever input tokens are available and output can be calculated. Because PN workflows are very loosely coupled, they are natural candidates for managing workflows that require parallel processing on distributed computing systems. For more information about these and other Kepler directors, please see section 5.2 of the Kepler User Manual.
