State-transition systems communicating by shared variables have been the underlying model of choice for applications of model checking. Such formalisms, however, have difﬁculty with modeling process creation or death and communication reconﬁgurability. Here, we introduce “dynamic reactive modules”, (DRM) a state-transition modeling formalism that supports dynamic reconﬁguration and creation/death of processes. The resulting formalism supports two types of variables, data variables and reference variables. Reference variables enable changing the connectivity between processes and referring to instances of processes. We show how this new formalism supports natural parallel composition and reﬁnement through trace containment. DRM provide a natural language for modeling (and ultimately reasoning about) biological systems and multiple threads communicating through shared variables.