This paper presents a description of Modelling & Simulation as used in the Virtual Systems Research Centre and issues discussed in previous FAIM and other papers, such as phases in a simulation project, Verification, Validation & Accreditation, and the use of simulation as a tool to reduce uncertainty. The role of the human in various phases/activities in simulation projects is highlighted. Two models for Information Fusion, the JDL and JDL-U model, are discussed. Subsequently, the activities and phases in a Modelling & Simulation project are placed in the context of the JDL-U model. This comparison shows that there are very strong similarities between the six (0-5) levels in the JDL-U model and activities/phases in Modelling & Simulation projects. These similarities lead to the conclusion that the JDL-U model with its associated science base can serve as a novel reference model for Modelling & Simulation.