Renew (The Reference Net Workshop) is a Java-based multi-formalism editor and simulator that provides a flexible modeling approach based on, but not limited to, reference nets.

Petri nets are a well established means to describe concurrent systems. Over the years, numerous extensions to the basic formalism have been proposed to account for abstract data types, object-orientation, hierarchies or new arc types.

Among them is the reference nets formalism, where tokens can be references to arbitrary objects, especially other nets, thus allowing nested net models. It allows Java inscriptions, has built-in List and Tuple types, offers test, inhibitor and flexible arcs and has a powerful synchronization mechanism.