Event Structure Spans for Nondeterministic Dataflow

A compositional semantics for nondeterministic dataflow processes is described using spans of event structures; such a span describes a computation between datatypes, themselves represented by event structures, as itself an event structure. The spans of event structures represent certain profunctors (a generalisation of relations) used previously in a compositional semantics of nondeterministic dataflow and in the semantics of higher-order processes. Deterministic spans of event structures are shown to correspond to stable continuous functions and their semantics of dataflow to reduce to the usual least fixed-point semantics of Kahn.