Specification of Control Flow in Ptolemy

Researchers: Bilung Lee, Xiaojun Liu
Advisor:Edward A. Lee

Most modern systems include control functionality for the proper sequencing of the computation tasks, and switching and coordinating between different operation modes. Finite state machines (FSMs) have long been used to specify control flow for control-dominated problems. In large systems, however, the control functionality can become so complex that the flat, sequential FSM model becomes impractical.

Hierarchical concurrent FSMs (HCFSMs) increase the usefulness of FSMs by extending with structuring and communication mechanisms. However, most formalisms that support HCFSMs, such as Statecharts [1] and its variants, tightly integrate the concurrency semantics with the FSM semantics. In contrast, we add hierarchy and heterogeneity to the FSM. This allows the FSM to be hierarchically combined with various concurrency models, in particular dataflow [2], discrete events [3] and synchronous/reactive [4] models. In this heterogeneous model, the semantics of FSM, concurrency and hierarchy are naturally supported. Our scheme decouples the FSM from the concurrency models, enabling selection of the most appropriate concurrency model for the problem at hand.

An FSM domain has been developed in Ptolemy and is integrated with the existing SDF and DE domains. Continuing work is to integrate the FSM domain with the SR domain. In addition, we will use the infrastructure of the FSM domain as our prototype to build a new *chart [5] domain in Ptolemy II.

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Last updated 03/22/99