Process Modelling with BPMN: Core Elements, Events, Gateways and Subprocesses
This domain tests whether you can read and construct BPMN models correctly, especially control flow, event triggers and gateway semantics.
Core notation
A BPMN process is drawn in a pool; lanes partition responsibilities. Core elements include tasks (user, service, script, manual), sequence flows (control within a pool), message flows (communication between pools), data objects and annotations. Events are start, intermediate or end; triggers include none, message, timer, error, signal, conditional and terminate. Gateways control splits and merges: exclusive (XOR, one path), inclusive (OR, one or more), parallel (AND, all paths), event-based (wait for the first event) and complex.
Subprocesses
An embedded subprocess contains a flow; a call activity reuses a separate process. Boundary events attach to activities and can be interrupting or non-interrupting. Event subprocesses handle exceptions inside a process scope.
Worked example
An order process receives an order (start message), checks stock (user task), and uses an exclusive gateway: if stock is available, reserve and ship; if not, backorder. A timer boundary event on the stock check escalates after two hours. A parallel gateway splits invoicing and shipping, which must both finish before the end. Reasoning: XOR chooses one business path; AND synchronizes independent work; the boundary timer handles a delay without abandoning the task.
Traps
Do not use message flows inside one pool. Every XOR split needs conditions or a default. Do not model a parallel gateway when paths are alternatives. Avoid multiple start events in one pool without clear triggers. A terminate end event stops the whole process instance, not just a branch.