A sequence flow is the connector between two elements of a process. You can set conditions on sequence flows, and set one as the default.
Standard Sequence Flow
Once an element is visited during the process execution, all outgoing sequence flows are followed (assuming no errors occurred). This means that the default nature of BPMN 2.0 is to be parallel: two outgoing sequence flows will create two separate, parallel paths of execution.
Although any BPMN element can have multiple sequence flows leading directly from it, we recommend using Gateways to help keep the structure of your model clear.
|An optional unique ID for this element. The modeller will assign a random ID if left blank
|A name for this element
|An optional description for this element
|A UEL Expression that must resolve to true or false
|If checked this sequence flow will be treated as the default, and be followed if no other flows have a true condition
Conditional Sequence Flow
A sequence flow can have a condition defined on it. When a BPMN 2.0 activity completes, the default behaviour is to evaluate the conditions on all of the outgoing sequence flows. When a condition evaluates to true, that outgoing sequence flow is followed. When multiple sequence flows are selected that way, multiple executions will be generated and the process will continue in a parallel way.
Note: The above holds true for BPMN 2.0 activities (and events), but not for gateways. Gateways will handle sequence flows with conditions in specific ways, depending on the gateway type.
Default Sequence Flow
All BPMN 2.0 tasks and gateways can have a default sequence flow. This sequence flow is only selected as the outgoing sequence flow for an activity if, and only if, none of the other sequence flows could be selected, ie it will only be followed when all other conditions evaluate to false. Conditions on a default sequence flow are always ignored.
You can read more about sequence flows in the workflow Making Decisions - Gateways and Sequence Flows reference article