  Simulation models have been described using different perspectives, or
worldviews. In the process interaction world view (PI), every entity is modeled
by a sequence of actions describing its life cycle, offering a comprehensive
model that groups the events involving each entity. In this paper we describe
piHyFlow, a formalism for representing hybrid models using a set of
communicating processes. This set is dynamic, enabling processes to be created
and destroyed at runtime. Processes are encapsulated into piHyFlow base models
and communicate through shared memory. piHyFlow, however, can guarantee
modularity by enforcing that models can only communicate by input and output
interfaces. piHyFlow extends current PI approaches by providing support for
HyFlow concepts of sampling and dense (continuous) outputs, in addition to the
more traditional event-based communication. In this paper we present piHyFlow
operational semantics using the concepts of simulator and component.
