Summary

Model parsimoniously for an engineering question. A model is a purposeful reduction of a system. Preserve the distinctions needed to answer the question; omit distinctions that do not contribute to it. Parsimony means adequacy without unnecessary representation, not minimality for its own sake. Build and maintain the model only while the engineering leverage it provides justifies its carrying cost.
Externalize engineering knowledge and intent. Models can expose architecture, obligations, dependencies, invariants, provenance, costs, and other properties that would otherwise have to be reconstructed from implementation and context. Different questions may require different models of the same system.
Choose degrees of freedom deliberately. Every representation leaves some choices open. Reduce consequential freedom where doing so improves reasoning or control; preserve freedom where realization can safely remain open, or where later information can support a better choice.
Maintain the correspondences you depend on. Multiple representations create correspondence obligations. Derivation, generation, validation, shared identity, and other mechanisms can keep related representations sufficiently consistent for their intended uses.
Distinguish correspondence from governance. A model may describe another artifact, or realization may be required to follow the model. Decide which representation owns each consequential fact and which consumers must follow it.

Modeling gives engineering judgment a durable representation. It does not establish that an agent understood that representation correctly, that the resulting artifact realizes it, or that the property continues to hold as the system changes. Those are problems of Alignment, which Chapter 3 takes up.

Modeling principle

Externalize engineering knowledge and intent into explicit, structured models that both engineers and agents can reason through.

Appropriate representations make broader engineering questions tractable and make additional properties available for Alignment.