MMP.18:4.4 - Impose the joint conditions before choosing execution order

Combine the component relations and interface conditions for the same modeled situation. Shared boundary values and initial conditions must satisfy that joint formulation. Redundant equations can express a useful invariant; contradictory equations expose incompatible assumptions or a failed identification of the shared quantities.

Feedback can require a joint solve. Suppose the selected same-instant relations are x=1+y and y=x/2. Substitution gives x=2 and y=1. Starting from y=0 and calling the first model once, then the second, returns x=1 and y=0.5; those values fail x=1+y. That call order is only one unfinished computation of the joint relation.

Choose between a common solve and separate interacting computations from the available capabilities and error needed by the answer. For time-dependent components, specify which inputs are held, interpolated or extrapolated between communication times, how events are synchronized, and whether a proposed step can be repeated. These are computation assumptions unless the actual subject has that delay or sampling behavior.

Compare the obtained exchange against the joint conditions and the required result. A residual can reveal a mismatch. Turning a small residual into an error bound needs the relevant conditioning or stability argument; CMP.8 supplies that approximate-computation work. CMP.14 supplies interaction between computations. More iterations cannot repair an incompatible physical or statistical premise.