ValueApproximationIfc

An approximation of downstream value, evaluated at a post-decision state — the V̄ of approximate dynamic programming (§4.5.5).

This is the piece only the modeler can supply, and separating it is the point: it can be unit-tested with no simulation, swapped between a computed form and a fitted one without touching the policy that uses it, and shared between policies.

Not ValueFunctionIfc, which this was called until a review noticed that ksl.utilities.moda.ValueFunctionIfc already exists — also a fun interface, also with a value(...) method, and used by MODAModel and PDFModeler. The two mean different things: MODA's maps a criterion's score onto a common value scale, and this one estimates cost-to-go. A study scoring decision policies on several criteria would import both, and the collision would surface as an import alias in user code rather than in the library.

Inheritors