MMP.Preface:3.5 - Simplify, diagnose and revise for the required consequence

MMP.9 starts with a source evolution law and quantities to retain. It derives their change, identifies the contribution that depends on removed detail and constructs a replacement through elimination, memory, added state, approximation or a sufficient bound. Initial conditions, inputs and the requested horizon determine whether the replacement serves the question. MMP.11 can supply a family for a still-unknown replacement relation.

MMP.17 constructs a cheaper supplier for selected source-model responses. Choose the responses and input region from their intended use, build the replacement, and refine or return to the source where approximation changes the answer. Retaining a value can be insufficient when the receiver needs a derivative, tail event or explanation.

MMP.18 connects models through the quantities and conditions they exchange. Translate between their quantities and scales, supply any omitted influence needed by the connection, and retain shared information. Preserving a total amount, a constant field or a joint probability law requires different conditions on that connection. Matching software inputs and outputs does not establish those conditions.

MMP.14 helps when available observations reveal a consequential prediction failure, or a proposed use makes a comparison worth performing. Choose a discrepancy relevant to that use, derive predictions for comparable records, locate the mismatch and change the implicated relation or assumption. Recalculate the receiving consequence. Several repairs may explain one discrepancy; predictive improvement alone does not identify its cause. Existing records, an algebraic comparison or a restricted use can be sufficient.

When a premise or question changes, B.5.RR identifies the reasoning that depends on it and derives the revised consequence. If the argument must first be recovered, use B.5.RA. B.5.MPC.R develops the comparison when the difficulty concerns a connection among physical, mathematical and computational accounts. The repair may belong to subject assumptions, observation, mathematical formulation or computation.

These contributions admit several entry points and returns. A changed reporting procedure can require a new probability law while leaving the choice criterion intact. A changed criterion can require another instruction while leaving the reporting law intact. A changed intervention can require revising the model’s mechanisms. Preserve each still-useful result and reconsider the part whose conditions changed.