The dataflow metaphor In the dataflow model the execution is driven by the availability of data and the sequencing is only constrained by data dependencies. This model does not require an explicit management of parallelism, it is implicit. Operations on the dataflow graph are units of potentially fine-grain parallelism. In a hardware dataflow machine, parallelism is achieved by having several functional units executing operations simultaneously. The metaphor of a virtual dataflow machine can be used to explain the Distributed Prograph model.
Parallelism is implicit in the dataflow model.
However for safety and performance reasons it is felt that the programmer should retain control of the parallelism in the Distributed Prograph model. The safety concern arises from the existence of side-effects and global variables. Distributed Prograph aims at executing a single application on a set of machines. The application is initiated on the user machine. Annotated portions of the application graph can then be sent to remote processors for execution.