Explanation

The why behind the design — the reasoning you reach for when the how-to and reference don't tell you which way to lean.

• The spec pattern — why the modelling API is declarative values applied at explicit moments, and what that buys you (reusable, serializable, comparable, derivable scenarios).
• Engine architecture — how the geomodel is constructed: isochore build-down, structural fidelity, and the Monte-Carlo regeneration seam.

For the layer map and the coupling rule, see Architecture & the DAG.