Model Fidelity vs. Model Maintainability: The MBSE Tradeoff Nobody Talks About

As MBSE adoption matures, programs are discovering that high-fidelity models become liabilities when teams lack the resources to maintain them. This analysis proposes a fidelity calibration framework tied to program phase and risk profile.

The Model Fidelity Trap

The aspiration in MBSE is to have a complete, high-fidelity model that serves as the authoritative system description. The reality on mature programs is more complicated.

Fidelity vs. currency tradeoff: High-fidelity models require proportionally higher maintenance effort. Programs that can't sustain that effort end up with models that diverge from the design baseline — sometimes without anyone noticing.

Phase-appropriate fidelity: The framework proposes different fidelity targets for concept, preliminary design, detailed design, and sustainment phases. Increasing fidelity to match design maturity is more sustainable than maintaining maximum fidelity throughout.

What to model at high fidelity: Interfaces, behavioral specifications for safety-critical functions, and configuration data should always be high-fidelity. Structural decomposition and internal component design can tolerate lower fidelity in many programs.

Practical recommendation: Establish explicit fidelity contracts at the subsystem level. Make the fidelity level visible to all model consumers so they understand the limitations of what they're reading.