This PR implements resolutions to the following issues, as approved in KerML FTF2 Ballots #5 and #6 and SysML v2 FTF 2 Ballot #8:

• KERML_-132 Constructor invocation expressions are semantically inconsistent
• KERML_-222 validateParameterMembershipOwningType will fail for ConstructorExpressions
• SYSML2_-766 Constructor expressions in SysML

Previously, an invocation expression where the invoked type was not a function acted as a constructor for an instance of the invoked type. The resulting usage was both typed by the invoked type and a subset of Performances::evaluations. But, if the invoked type was a data type or structure, then this was a semantic inconsistency, because Performance (a supertype of evaluations) is disjoint with DataValue and Object. The resolution to KERML_-132 fixes this by introducing a new kind of constructor expression and requiring that the invoked type of an invocation expression be a behavior or function.

Abstract Syntax

1. InstantiationExpression
   • Added as a abstract superclass of InvocationExpression and ConstructorExpression.
   • Defines a derived property instantiatedType, which is the Type invoked/instantiated by the expression.
   • In order to allow more consistent parsing, the instantiatedType of any kind of InstantiationExpression, other than an OperatorExpression or TriggerInvocationExpression (in SysML), is parsed as a member of the expression. (There are special derivation rules for the instantiatedType of an OperatorExpression or TriggerInvocationExpression.)
   • An InstantiationExpression must own its result parameter.
2. InvocationExpression
   • An InvocationExpression is required to specialize the instantiatedType, as before.
   • The instantiatedType of an InvocationExpression must be a Behavior, normally a Function.
   • If the instantiatedType is a Behavior that is not a Function, then the InvocationExpression is still typed by the Behavior, with its result bound to the expression itself. This allows non-Function Behaviors to still be essentially "constructed" using an InvocationExpression, as before. (This does not cause semantic problems, because it is acceptable to specialize a Performance of the Behavior to an Evaluation that returns itself.)
   • The arguments of an InvocationExpression are parsed as FeatureValues of ownedFeatures of the expression itself, as before.
3. ConstructorExpression
   • Added to replace the use of InvocationExpressions with constructor semantics.
   • The result of a ConstructorExpression is required to specialize the instantiatedType.
   • The arguments of a ConstructorExpression are parsed as FeatureValues of ownedFeatures of the result of the ConstructorExpression. (In this way, a value of the instantiatedType is "constructed" as the result of the ConstructorExpression, while the expression itself can still be typed as an Evaluation.)
4. FeatureReferenceExpression
   • FeatureReferenceExpression is also updated with a new validation constraint requiring that it own its result parameter.

Note. The Pilot Implementation previously inserted an owned result parameter for all kinds of expressions. Now this is only done for InstantiationExpressions and FeatureReferenceExpressions.

Concrete Syntax

The concrete syntax for a constructor expression is similar to that of an invocation expression, but preceded by the keyword new.

class Member {
    feature firstName : String;
    feature lastName : String;
    feature memberNumber : Integer;
    feature sponsor : Member[0..1];
}
feature thisMember = new Member("Jane", "Doe", 1234, null);
feature nextMember = new Member(
    firstName = "John", lastName = "Doe", sponsor = thisMember,
    memberNumber = thisMember.memberNumber + 1);

Model Libraries

Kernel Semantic Library

1. Performances – Add constructorEvaluations as the base feature of all ConstructorExpressions. constructorEvaluations is a specialization of evaluations that restricts the multiplicity of its result parameter to 1..1, requiring a constructorEvaluation to result in a single value.
2. Triggers – Use the new syntax to construct the result values for TriggerWhen and TriggerAt.

SysML Domain Libraries

1. Analysis Domain Library, SampleFunctions – Use the new syntax to construct the result value for the calculation definition Sample.
2. Metadata Domain Library, RiskMetadata – Use the new syntax to construct the enumerated values of the enumeration definition RiskLevel.
3. Quantities and Units Library, MeasurementReferences – Use the new syntax to construct the value of the attribute usage one.