Discrete-event simulation is used to analyze production and logistics problems in many areas such as commerce, defense, health, manufacturing and logistics. Commercial-off-the-shelf (COTS) Simulation Packages (CSPs) are black box visual interactive modelling environments that support the development of such simulations. These include CSPs such as Arena™, Anylogic™, Flexsim™, Simul8™, Witness™, etc. There have been various attempts to create distributed simulations with these CSPs and their tools, some with the High Level Architecture (HLA). These are complex and it is quite difficult to assess how a set of model/CSPs are actually interoperating. As the first in a series of standards aimed at standardizing how the HLA is used to support CSP-based distributed simulations, the Simulation Interoperability Standards Organization’s (SISO) CSP Interoperability Product Development Group (CSPI PDG) has developed and standardized a set of Interoperability Reference Models (IRM) that are intended to clearly identify the interoperability capabilities of CSP-based distributed simulations. This paper presents the standard and summarizes the current activities of the PDG.