In some cases employees start requesting, in other accountancy start confirming. Yes, business processes in the world are not started from the same occasion. Rather multiple starting occasion (we call "Trigger") should be prepared in most of business processes. This theme in the BPMN lecture series is "Multiple Triggers."
BPMN Sample: Multiple Start
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There also are some cases not started by human.
- Automatically a duty be allocated to someone in certain time.
- Data transfer from external device (like sensors) make duty.
In Workflow below, for example, Accountancy proceeds [1a. Task] every Monday morning. (There's a possibility of proceeding at other timing by his own judgment.) And [2. Task] will be directly allocate by Message Start Event in some case. By the way, when the first task is input work by human, data transfer from external device may be supposed for simplification and labor saving. If you can trust your external devices, the first task by human could be omitted in Workflow.