The Model Fidelity Hierarchy: From Text to Conceptual, Computational, and Executable Model

Model-based systems engineering applies a variety of model kinds, each with its own fidelity and exactness level. Based on experience we gained while modeling an aircraft landing gear with the objective of numerically defining its various parameters that fulfill engineering and safety requirements, we present the model fidelity hierarchy (MFH). At this hierarchy's bottom, vaguest level, is spoken language, followed by free written text, conceptual model, its augmentation with computational capabilities, and finally an executable version of that model. Using object-process methodology (OPM ISO 19450) with its computational extension, we present this hierarchy by describing the landing gear model as it progresses through these levels, and the kinds of mistakes revealed while transitioning from one level to the next. The MFH, identified and defined in this article, is made possible by using OPM, which enables these level transitions to be information lossless, providing the most value while requiring the minimal effort. The ability of this continuous, seamless modeling approach to detect errors with increasing accuracy justifies our OPM approach, as errors revealed in this early system lifecycle stage are exponentially less costly to correct than those revealed downstream.