DMN17 — Ambigous operational semantics for the implicit conversions and constraints

The implicit conversions are defined in the FEEL chapter, in section 10.3.2.9.4 Type conversions.

The constraints for the DMN types are defined in section 7.3.3 ItemDefinition metamodel.

It is not very clear when these conversions or constraints are applied / checked:

• Are they applied only when the values are bound to a variable (e.g. expression is a direct child of a DMN element that contains also an Information Item) or every time an expression is evaluated?
• Are they applied only when FEEL expressions / textual are evaluated, or for boxed expressions as well? The boxed expressions are defined outside of the FEEL chapter.

I am leaning towards checking the above only when a binding takes place (a value is bound to a variable of a known type). For example, after the evaluation of the body of Decisions, Invocable, Context Entry, and Binding.

The main reason is to keep things simple and be consistent with common patterns in other PLs / DSLs.