The Business Process Model and Notation (BPMN) below figure depicts the message flows between two participants, the Ward and the Pharmacy, independent BP and may have been constructed separately. The synchronization between both participants is a necessary behavioral property for successful collaboration. The Ward-Pharmacy interaction choreography is realizable if that property is individually proved for each participant. From the pharmacy participant's perspective, drugs delivered must be guaranteed by sending a message to the ward participant prior a purchase order would be made or sent; while from the ward participant's perspective, by sending a message to the pharmacy participant with enough time in advance to have the required drugs to begin medical treatment.
