Specifying Simulation Commitments Early in System Design: Introduction to the EFSUT Methodology

Engineering programs increasingly rely on simulation for early design decisions, yet a simulation’s obligations—the specific questions it must answer and observations it must provide—are often left implicit until late in development. The Experimental Frame–System Under Test (EFSUT) methodology addresses this gap by requiring these commitments to be specified explicitly early in system design. EFSUT organizes simulation around four core elements—questions, experimental conditions, models, and results—and defines formal relations that clarify how tests are derived and which models can meaningfully be evaluated. We demonstrate the methodology in two contrasting domains, showing how an informally stated motivating question leads to a structured sequence of experimental conditions and guides model selection and interpretation. Compared with existing approaches to model adequacy and digital-engineering traceability, EFSUT provides a clear, question-driven foundation that links stakeholder intent to model evaluation in a transparent, defensible manner. This approach is particularly valuable for aligning simulation practice in multi-model and system-of-systems contexts. Future work includes the automated derivation of Experimental Frames, integration with digital-thread toolchains, and more broadly, development of a lifecycle-spanning, formalized question-driven framework to support evaluation, optimization, and adaptation where traditional requirement-based methods fall short.