UMLR — Relation of message arguments to signature parameters ambiguous

In section 14.3.18, the constraints 3 and 4 say that the arguments of message must correspond to the parameters/properties of the signature (operation/signal). This leads to an ambiguous siuation in some situations. For example:

Let's assume there is an operation with the following signatur op1(x:String[*], y:String[*]) or a Signal S with two properties
S::p1 : String[0..1]
S::p2 : String[0..1]

Since there is no direct relationship between an argument and a parameter/property it is not possible to determine what argument belongs to the first parameter/property (list in case opf operation example) and what to the second one.

This problem always occurrs when two parameters/properties of the same type are specified in a sequence and the first one has either an optional multiplicity or an upper bound equals *.

A possible solution is to introduce an additional metaclass MessageArgumentSpecification, which should be contained by Message instead of ValueSpecification directly, with the following structure:

MessageArgumentSpecification{
refersTo: TypedElement [1]

arguments : ValueSpecification [1..*]

}

It might be also considerable to keep the association between a referenced element and an argument bilateral. In this case, the association between Message and MessageArgumentSpecification should be ordered.