Apply/PolicyReference/SharedVariableReference object - Replace property name 'Expression' with 'Argument'

[cdanger]

Looking at more and more examples of JACAL policies, I think 'Argument' would be more natural / intuitive than 'Expression' in Apply objects as well as PolicyRefences and SharedVariableReferences. (The property type remains the same - 'ExpressionType').

{
    "Apply": {
        "FunctionId": "f",
        "Argument": [  ... the args passed to function f...     ]
    }
}

So the change to ACAL:

class ApplyType extends NonLiteralExpressionType {
+ Description: String [0..1]
+ FunctionId: IdentifierType [1]
+ ExpressionArgument: ExpressionType [*] {ordered, nonunique}
}
...
class PolicyReferenceType extends PatternMatchIdReferenceType {
+ ExpressionArgument: ExpressionType [*] {ordered, nonunique}
}

Then rename the property in JACAL schema accordingly.

[humantypo]

It seems like we should choose one or the other to be consistent.

[steven-legg]

I was thinking that "Argument" would be a more natural name in those cases while I was editing the examples. The complication is that ExpressionType is used in other places where "Argument" would not be a natural name. Not a problem for the JSON Schema but the XSD uses the Expression element for the base of an element substitution group. The XACML 4.0 spec would have to account for the Expression and Argument properties both being translated into the Expression element.