BPMN2 — Called conversations without keys of the caller

Called conversations might have messages that don't have the correlation keys of the caller. Clarify whether this is allowed or not.

Called collaborations can have messages that don't have the correlation
keys of the caller. The internal structure of messages is not specified
in BPMN, but correlation keys applying to message flow establish
property requirements on the contents of the message. The correlation
keys applying to a message flow are all the keys of the containers of
the message flow, including containers transitively through calls of
collaborations or choreographies.
Above Figure 8.18 (The Correlation Class Diagram) insert a new
paragraph:
Correlation can be applied to message flows in Collaboration and
Choreography, as described in Chapters XXXCollaboration and
XXXChoreography. The keys applying to a message flow are the keys of
containers or groupings of the message flow, such as Collaborations,
Choreographies, and Conversation Nodes, and Choreography Activities.
This might result in multiple correlation keys applying to the same
message flow, perhaps due to multiple layers of containment. In
particular, calls of Collaborations and Choreographies are special
kinds of Conversation Nodes and Choreography Activities, respectively,
and are considered a kind of containment for the purposes of
correlation. The correlation keys specified in the caller apply to
message flow in a called collaboration or choreography.
Disposition: Resolved