System Simulation (or Systems Modeling and Simulation) is the ultimate arbiter of whether a product is meeting its given performance objectives. As such, System Simulation incorporates the end effects of all sub-systems and component in determining overall product performance. Traditionally, in Engineering Design and Simulation circles, System Simulation has been synonymous to Model Based Systems Engineering (MBSE), which INCOSE defines as a “formalized application of modeling to support system requirements, design, analysis, verification and validation activities beginning in the conceptual design phase and continuing throughout development and later life cycle phases.” However, in recent years with the popularizing of the Digital Twin and the Internet of Things (IoT), MBSE is now viewed as a component of System Simulation and not its totality. In addition to MBSE, System Simulation now includes items such the methods for combining different data sources (physics based predictions, test data, field data, etc,) that are statistically analyzed (Bayesian Information Fusion) to make a business decision (as opposed to simply an engineering design decision). It has also expanded its reach to include not only engineering design decision, but the entire product experience lifecycle including, product conception, manufacturing, field usage, etc.