DMN17 — "instance of" not possible with some built-in functions

some built in functions are overloaded in that they can have multiple signatures. So, say, performing an "instance of" to compare against the function "min" is meaningless as the signature is not known unless it is invoked.

Unless the type system is to take into account overloaded functions?

Add existing type qualifiers to grammar

Currently, the FEEL grammar notation for function definitions does not support optional parameters and variable arguments.

The proposal adds such features allowing the specification of builtin functions such as min(), max() and substring()