SAFe Knowledge Base » Model-Based Systems Engineering
Model-Based Systems Engineering
All models are wrong, but some are useful.
—George E. P. Box, "Robustness in the Strategy of Scientific Model Building" [1]
Definition: Model-Based Systems Engineering (MBSE) is the practice of developing a set of related models that help define, design, simulate, and document a system under development.
MBSE is the application of modeling systems as a cost-effective way to explore and document system characteristics. By testing and validating system characteristics early, models facilitate timely learning of properties and behaviors, enabling fast feedback on requirements and design decisions. Models provide an efficient way to explore, update, and communicate system aspects to stakeholders while significantly reducing or eliminating dependence on traditional documents.
MBSE historically focused on expressing and recording requirements, design, analysis, and verification information [2]. As modeling technology matures, it provides even more value by accelerating learning (e.g., simulation) and providing better insights into the physical world (e.g., digital twins) [3]. Both are important to evolve live systems and enable Enterprise Solution Delivery.
Although models are not a perfect representation of a system, they provide knowledge and feedback sooner and more cost-effectively than implementation alone. And they allow the simulation of complex system and system-of-systems interactions with appropriate fidelity to accelerate learning. In practice, engineers use models to gain knowledge and to serve as a guide for system implementation. In some cases, they use them to directly build the actual implementation (e.g. electrical CAD, mechanical CAD).
Details
Lean practices support fast learning through a continuous flow of development work to gain fast feedback on decisions. MBSE is a discipline and a Lean tool that allows engineers to quickly and incrementally learn about the system under development before the cost of change gets too high.
Models are used to explore system elements’ structure, behavior, and operational characteristics, evaluate design alternatives, and validate assumptions faster and earlier in the system life cycle. This is particularly useful for large and complex systems—satellites, aircraft, medical systems, and the like—where the solution must be proven practical beyond all possible doubt before, for example, launching into space or connecting to the first patient. Models also record and communicate decisions that will be useful to others. This information serves as documentation for Compliance, impact analysis, and other needs. In SAFe, model information is recorded as part of the Solution Intent, most often created by the work of Enablers.
The following sections provide guidance on adopting MBSE.
