Currently it is not possible to model a choreography that involves a particular
sub-choreography being performed concurrently with multiple participants.
Examples of this type of choreography may be in a request for quote scenario,
where we would want to send the RFQ document to 'n' potential suppliers in
parallel, and then select the "best" quote.
 
The limitation is that currently the repetition construct (workunit with a
repetition condition) effectively executes the repeated activities in sequence
(i.e. one at a time), not allowing any concurrency.