SMM11 — functor should have an enumeration defined in the spec

In SMM, a binary measure has a functor.

Examples in the spec (instance models) suggest functor values like “sum”, “difference”, “times”, “divide”.

This sounds like functor should have an enumeration defined in the spec, like also accumulator has for a collective measure.

However, SMM does not do that for functor. Why not? It is rather similar (see also that accumulator has a value “sum” ..).

Introduce an Enumeration type for functor, with enumeration values “sum”, “difference”, “times” (or “product”) and “divide”, and also “custom”. In case the BinaryMeasure’s functor has value “custom”, also specify customFunctor, being an association to Operation (with association end name customFunctor).