South East Training - Business Process Modelling Toolkit
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- So far we have seen the use of start and end events to define the boundaries of processes and sub-processes. Start events act as triggers to initiate sequence flow while end events define the end state of a path.
- BPMN, however, also includes a variety of intermediate events that can be used in sequence flow or attached to the boundaries of activities or sub-processes.
- The diagram below shows two versions of the message intermediate event, one catching (similar to the message start event) and one throwing (similar to the message end event).
- The other is a timer intermediate event. The timer intermediate event represents a delay in the flow. It is often used in event gateways where it initiates an exception path after a given period if the normal flow is delayed waiting for a different event to occur, e.g. the receipt of a message.
Intermediate Events - Examples
- Delay using an Intermediate Timer Event
- The top diagram shows how the intermediate timer event might be used to introduce a delay. In the example, HR is waiting to see if they have enough interest in a training event before scheduling it. Rather than doing this continuously, they have decided to check numbers at three-day intervals. The XOR Gateway will only allow scheduling once four or more nominations have been received, otherwise, another three-day delay is introduced.
- Event Gateway
- The diagram on the bottom illustrates the use of an Event Gateway. The gateway is initiated by which-ever following intermediate event occurs first. In this case, the bidder is expecting a positive or negative response within a week. Receipt of a response will trigger the appropriate intermediate message event to initiate the following activity. If no response is received within that time, the intermediate timer event will open the path to allow the bidder to contacts the customer for an update.