Implementation issue from Gary:

. Example: request for quote, while waiting for suitable quote (on refresh loop),
until quote accepted

   Interaction: --> request for quote
     Interaction: <-- quote  
     workunit guard=hasDurationPassed(30sec) block=true
                   repeat=!quoteAccepted {
           Interaction <-- updateQuote
      }Interaction: --> quote accepted

. Currently only possible with parallel construct setting state variable to indicate
when quote is acceptable, as quote provider as no means to detect when quote
has been accepted, and therefore break out of the loop

. Suggestion: having a 'hasExchangeOccurred' to finish the loop once the quote
accept has been received


Send rfq                            Receive rfq
Receive quote                       Send quote
Parallel{                           Parallel{
    when quoteAcc                       when .....
        Send quoteAcc                     Receive quoteAcc
        [rec quoteAcced]                  [rec quoteAcced]
    when refresh &&                     when refresh &&
          !quoteAcced ..                   !quoteAcced
}                                   }