Dynamic Dataflow Modeling in Ptolemy II - Ptolemy Project ...

or certain aspects of the system. Small, specialized languages and tools based on different
MoCs have proved to be very useful due to their appropriateness for certain domains of
application and their formal properties resulting from the constrained semantics. Using
hierarchy, one can divide a complex model into a tree of nested submodels with each
level being homogeneous (each described by a particular MoC), thus allowing different
MoCs used at different levels. Figure 3.7, which is directly borrowed from [21], shows a
hierarchical model in Ptolemy II. Atomic actors, such as A1 and B1, appear at the
bottom of the hierarchy. Composite actors, such as A2, can further contain other actors,
so the hierarchy can be arbitrarily nested. Director2 is called the local director of A2
while Director1 is called the executive director of A2. Hierarchical heterogeneity is
achieved by having different directors at different levels of the model.
Figure 3.7 A hierarchical model in Ptolemy II
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