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

Dataflow programming has come a long way since its use in the signal processing
community. Various programming environments based on this model of computation
have been developed over the years. Various specialized dataflow models of computation
have been invented and studied. (We will give a brief overview in section 2). Various
scheduling algorithms based on different criteria pertinent for specific applications have
been proposed. It is still a fruitful area of active research due to its expressive way to
represent concurrency for embedded system design.
1.3 A Software Environment for Experimenting with MoC ---- Ptolemy II
The Ptolemy project at University of California at Berkeley studies modeling, simulation,
and design of concurrent, real-time, embedded systems. The focus is on assembly of
concurrent components. The key underlying principle in the project is the use of well-
defined models of computation that govern the interaction between components [4].
Unlike most system design environments which have one or two built-in models of
computation, the Ptolemy kernel has no built-in semantics. Instead the kernel package
defines a small set of Java classes that implement a data structure supporting a general
form of uninterpreted clustered graphs (see Figure 1.1 taken from [6]), which provide an
abstract syntax that is not concerned with the meaning of the interconnections of
components, nor even what a component is.
The semantics is introduced in the actor package which provides basic support for
executable entities. However it makes a minimal commitment to the semantics of these
entities by avoiding specifying the order in which actors execute and the communication
mechanism between actors. These properties are defined in each domain where the
12