Abstract interpretation and indeterminacy

We present a semantic theory that allows us to discuss the semantics of indeterminate operators in a dataflow network. The assumption is made that the language in which the indeterminate operators are written has a construct that allows for the testing of availability of data on input lines. We then show that indeterminacy arises through the use of such an operator together with the fact that communication channels produce unpredictable delays in the transmission of data. Our scheme is to use special tokens called hiatons to obtain ordinary streams. This filtering process produces indeterminate behavior at the level of ordinary streams. We indicate how this can be justified using the formalism of abstract interpretation. We show that a particular fairness anomaly does not arise.