In section 11.8.15.5 "Association Ends" and 11.8.15.6 "Operations" of StructuredClassifier on p. 275 of the PDF version of the UML 2.5.1 specification, we see the definitions of these two items:
• /role : ConnectableElement [0..*]{union, subsets Namespace::member} (opposite
A_role_structuredClassifier::structuredClassifier)
The roles that instances may play in this StructuredClassifier.
and
• allRoles() : ConnectableElement [0..*]
All features of type ConnectableElement, equivalent to all direct and inherited roles.
body: allFeatures()->select(oclIsKindOf(ConnectableElement))
->collect(oclAsType(ConnectableElement))->asSet()
What is the intended derivation of /role? It is derived, but there is no OCL implementation given. The operation allRoles() returns both owned and inherited roles, but I assume that /role should not return any Features of the parents (returned from allFeatures()). It does subset member, so it might include some imported Elements.
Is this correct? Or is the allRoles() operation supposed to somehow implement the derivation of the /role attribute?
The derivation of role is simply given by {union}.
It is a derived union of all the attributes that subset role. So, no ocl is necessary. allRoles() is just for convenience. It is used in other constraints.