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.