1. What is BPMN
BPMN (Business Process Modeling Notation) refers to business process modeling and annotation, including how these graphic elements are combined into a business flow chart.
2. Basics of BPMN
The BPMN presented in this article contains only an introduction to stream objects. Flow object : It is the main graphic element that defines the business process, including three types: event, activity, and gateway.
Events : including start event, activity and end event. The start of an event is represented by a circle with a thin line, the activity in the middle of an event is represented by a rectangle with rounded corners, and the end of an event is represented by a circle with a thick line.
Activities (Activities) : A series of activities constitute intermediate events.
Gateways (Gateways) : Used to represent the branching and merging of processes, represented by diamonds. Only three common gateways are introduced here, each of which is divided into split and join gateways:
- Exclusive Gateway (XOR Gateway): only one path will be chosen
- Parallel gateway (AND Gateway): all paths will be selected at the same time
- Inclusive Gateway (OR Gateway): choose any path or multiple paths
3. An example diagram that conforms to well-structured layout
Here the green circle indicates the start of the event and the orange circle indicates the end of the event.
4. The meaning of well-structured layout
It is used to transform orchestrations with different structures but the same semantics into ones with unified structures to eliminate the diversity of construction structures.
The advantage of this is that when defining the formal semantics of orchestration, only the mapping from well-structured orchestration to workflow-net (WF-net) needs to be considered. In addition, well-structured orchestration is mainly to facilitate the mapping of BPMN orchestration to workflow-net (WF-net), without losing the generality of orchestration. In short, in order to facilitate the mapping of BPMN to WF-net.
5. Characteristics of well-structured layout
Well-structured orchestration has the following characteristics:
(1) There is one and only one output stream at the beginning of the event, but no input stream;
(2) There is one and only one input stream at the end of the event, but no output stream;
(3) The activity has only one input stream and one output stream;
(4) A fork gateway can only have one input stream and multiple output streams;
(5) A merge gateway can only have one output stream and multiple input streams;
(6) The gateway must be connected to an activity.
Note: The input flow and output flow are sequential flows: represented by a solid line with a solid arrow, which is used to specify the order in which activities are executed.
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Supplement: After conversion analysis [analysis process] , to draw BPMN that can be converted into Process Tree, there are the following suggestions:
- If there is a loop, cross-nesting of gateways should be avoided. The logic is clearer. More readable.
- The gateway in the loop should avoid extraneous branches and lead out of the loop. Otherwise, there will be ambiguity and cannot be converted into Process Tree.
- If there is a fork gateway, there must be a merge gateway to merge it back. Doing this also avoids cross-nesting of gateways.
- Real-world cases may not be able to fully meet the above requirements. If only to generate event logs, it needs to be converted into a Process Tree, and the cyclic event nodes can be repeated.
Attachment : BPMN online designer address