TY  - EJOU
AU  - Zeigler, Bernard P. 

TI  - Experimental Frame–System Under Test (EFSUT): A Principled Foundation for Model Choice and Lifecycle Management in Digital Twins
T2  - Digital Engineering and Digital Twin

PY  - 2026
VL  - 4
IS  - 1
SN  - 

AB  - As Digital Twin (DT) applications expand into complex, dynamic environments, a formal methodology is lacking to ensure that the embedded digital models remain adequate for specific stakeholder goals over time. This article introduces the Experimental Frame–System Under Test (EFSUT) methodology, providing a principled foundation for linking high-level stakeholder questions to the specific models capable of answering them. EFSUT organizes the digital engineering process around three core constructs: stakeholder questions, experimental frames that formalize observational requirements, and models related through morphisms. This structure allows developers to reason about model choice, reduction, and adequacy with technical rigor and transparency. To demonstrate the methodology’s impact on lifecycle management, we present a DT architecture for an example ecological system. Because the system is subject to seasonal variability and structural drift, the architecture embeds the DT in a continuous lifecycle of sensing, prediction, drift detection, and recalibration. This practical application illustrates how EFSUT strengthens digital engineering practice—from initial design to long-term model assurance. We conclude by discussing future research in automated frame derivation, Model-based System Engineering toolchain integration, and scalable decision pipelines. Research is also needed for formal verification of frame–model applicability and scalable simulation-based decision pipelines.
KW  - EFSUT methodology (experimental frame–system under test); modeling and simulation (M&S) formalism; discrete event system specification (DEVS); model morphisms; experimental frames; digital twin engineering; digital twin lifecycle management; systems theory & engineering; model-based systems engineering (MBSE); model reduction

DO  - 10.32604/dedt.2026.082492