Activities

An activity is work performed within a business process. When a token arrives at an activity, the process waits until the work is completed; the token then continues along the outgoing sequence flow.

Activities come in two kinds:

• Tasks — atomic units of work, such as executing a job, evaluating a decision, or waiting for a human or a message.
• Subprocesses — compound activities that contain their own flow: a Sub process embedded in the diagram, a Call activity invoking another process, or an Event sub process started by an event while its scope is active.

However different the work they perform is, all activities behave the same way towards the surrounding process — this page describes that shared behavior.

Markers

Markers are small icons at the bottom center of the activity shape that modify how the activity executes, without changing its type. ZenBPM supports the two multi-instance markers:

Marker	Icon	Description
Parallel multi-instance		Runs the activity once per element of a collection, with all instances created at the same time.
Sequential multi-instance		Runs the activity once per element of a collection, one instance after another.

Usage in BPMN

Every activity, regardless of its type, supports the following markup:

Markup	Description
zenbpm:ioMapping → zenbpm:input / zenbpm:output	Maps variables between the process scope and the activity's local scope. See Variables.
bpmn:multiInstanceLoopCharacteristics	A marker (not a separate activity type) that runs the activity once per element of a collection, sequentially or in parallel. See Multi-instance activity.
bpmn:boundaryEvent attached via attachedToRef	Reacts to errors, messages, or timers while the activity is active, and routes the process accordingly. See Boundary events.

The shared lifecycle:

1. A token arrives at the activity and input mappings are evaluated into the activity's local variable scope.
2. The activity performs its specific work — creates a job, evaluates a decision, waits for a message, or runs a child process.
3. On completion, output mappings propagate selected variables back to the parent scope. Without output mappings, no variables are propagated.
4. The token continues along the outgoing sequence flow. While the activity is active, attached boundary events can interrupt it or trigger parallel flows.

Related documentation

• Variables — variable scoping and mapping rules shared by all activities.
• Boundary events — handling errors, timeouts, and messages on a running activity.
• Multi-instance activity — the multi-instance marker in detail.

XML example

The common markup applied to one concrete activity (a Service task): variable mappings, a multi-instance marker running the task once per customer, and an error boundary event:

<bpmn:serviceTask id="Activity_NotifyCustomers" name="Notify customers">
  <bpmn:extensionElements>
    <zenbpm:taskDefinition type="send-notification" />
    <zenbpm:ioMapping>
      <zenbpm:input source="=campaign.id" target="campaignId" />
      <zenbpm:output source="=deliveryStatus" target="lastDeliveryStatus" />
    </zenbpm:ioMapping>
  </bpmn:extensionElements>
  <bpmn:multiInstanceLoopCharacteristics>
    <bpmn:extensionElements>
      <zenbpm:loopCharacteristics inputCollection="=customers" inputElement="customer" />
    </bpmn:extensionElements>
  </bpmn:multiInstanceLoopCharacteristics>
  <bpmn:incoming>Flow_In</bpmn:incoming>
  <bpmn:outgoing>Flow_Out</bpmn:outgoing>
</bpmn:serviceTask>

<bpmn:boundaryEvent id="Boundary_NotifyFailed" attachedToRef="Activity_NotifyCustomers">
  <bpmn:errorEventDefinition errorRef="Error_NotifyFailed" />
</bpmn:boundaryEvent>