Robust and informed decisions are important for the efficient and effective operation of installed production facilities. The paper discusses Information fusion (IF) including a generic model for IF, and situations for decision-making. The paper also discusses current and future use of manufacturing resource simulation for design/configuration, operational planning and scheduling, and service and maintenance of manufacturing systems. Many of these applications use IF in some way, as is explained in more detail for simulation based service and maintenance. An extension of the generic model for IF is presented which incorporates modeling and simulation, and active databases as used in a simulation based service and maintenance system at the authors’ laboratory