UMLR — OCL Syntax in expressions

When OCL is used in body of OpaqueExpressions it's unclear what syntax should be used - in particular whether keywords like "context:", "inv:", "pre:" should be used or not. Section 7.3.35 should, for OCL, reference the correct concrete syntax element in the OCL spec. Additional material for this issue:

At the moment in 7.3.35 there is just a 'style guideline' for how OCL constraints/expressions should be expressed using an OpaqueExpression
For interoperability there should be a stronger statement that OCL constraints must have language = "OCL".
Also it should be made clearer that such OpaqueExpressions should have type=Boolean