# Managing Subprocesses

Coordinate parallel work across departments, services, or approval chains by creating child subprocesses through fork transitions. Without
`CheckAllSubprocessesCompleted` and `DeleteSubprocesses`, every scheme that needs to wait for parallel branches or clean up active children
would require custom code. These built-in actions handle subprocess lifecycle in conjunction with the scheme's fork and merge transitions.

## How subprocesses work in Workflow Engine

A subprocess is a process instance that runs as a child of a parent process. Subprocesses are created through **fork transitions** on the
scheme, not through the `CreateProcess` action:

- **Fork transitions** (`IsFork="true"`) with `SubprocessInOutDefinition="Start"` create child subprocesses that execute in parallel.
- **Merge transitions** with `SubprocessInOutDefinition="Finalize"` bring subprocesses back to the parent.
- `CheckAllSubprocessesCompleted` checks the process tree for active children.
- `DeleteSubprocesses` deletes all child subprocesses.

`CreateProcess` is a separate action that creates independent process instances without a parent-child relationship. It is not tracked by
`CheckAllSubprocessesCompleted` or `DeleteSubprocesses`.

## Real-world scenario: employee onboarding

A company onboarding workflow assigns tasks across three departments when a new employee joins. The parent workflow forks into three
parallel subprocesses - one for IT (provision laptop), one for HR (enrollment), and one for Facilities (desk assignment). Each subprocess
runs independently. The parent waits until all three subprocesses complete before marking the employee as onboarded.

## Workflow scheme

The parent scheme forks into three subprocess branches. Each branch (`IT_Department`, `HR_Department`, `Facilities_Department`) runs as a
child process. When all three merge back, `CheckAllSubprocessesCompleted` allows the process to finalize.

![Employee onboarding workflow scheme](https://docs.workflowengine.io/images/plugins/basic-plugin/managing-subprocesses/onboarding-parent.png)

**Related capabilities:** `CheckAllSubprocessesCompleted` condition, `DeleteSubprocesses` action, fork/merge transitions, `CreateProcess`
action.

```xml filename="employee-onboarding.xml"
<Process Name="EmployeeOnboarding" CanBeInlined="false">
  <Designer />
  <Commands>
    <Command Name="CompleteIT" />
    <Command Name="CompleteHR" />
    <Command Name="CompleteFacilities" />
  </Commands>
  <Activities>
    <Activity Name="Start" State="Start" IsInitial="True"
              IsFinal="False" IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="100" Y="300" />
    </Activity>
    <Activity Name="LaunchTasks" State="LaunchTasks"
              IsInitial="False" IsFinal="False"
              IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="350" Y="300" />
    </Activity>
    <Activity Name="IT_Department" State="IT_Department"
              IsInitial="False" IsFinal="False"
              IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="700" Y="100" />
    </Activity>
    <Activity Name="HR_Department" State="HR_Department"
              IsInitial="False" IsFinal="False"
              IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="700" Y="300" />
    </Activity>
    <Activity Name="Facilities_Department" State="Facilities_Department"
              IsInitial="False" IsFinal="False"
              IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="700" Y="500" />
    </Activity>
    <Activity Name="Merged" State="Merged"
              IsInitial="False" IsFinal="False"
              IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="1050" Y="300" />
    </Activity>
    <Activity Name="Complete" State="Complete"
              IsInitial="False" IsFinal="True"
              IsForSetState="True"
              IsAutoSchemeUpdate="True">
      <Designer X="1400" Y="200" />
    </Activity>

  </Activities>
  <Transitions>
    <Transition Name="Start_LaunchTasks"
                To="LaunchTasks" From="Start"
                Classifier="Direct" IsFork="false"
                MergeViaSetState="false"
                DisableParentStateControl="false">
      <Triggers>
        <Trigger Type="Auto" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="LaunchTasks_IT"
                To="IT_Department" From="LaunchTasks"
                Classifier="NotSpecified"
                IsFork="true"
                MergeViaSetState="false"
                DisableParentStateControl="false"
                SubprocessInOutDefinition="Start"
                SubprocessStartupType="SameThread"
                SubprocessStartupParameterCopyStrategy="CopyAll">
      <Triggers>
        <Trigger Type="Auto" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="LaunchTasks_HR"
                To="HR_Department" From="LaunchTasks"
                Classifier="NotSpecified"
                IsFork="true"
                MergeViaSetState="false"
                DisableParentStateControl="false"
                SubprocessInOutDefinition="Start"
                SubprocessStartupType="SameThread"
                SubprocessStartupParameterCopyStrategy="CopyAll">
      <Triggers>
        <Trigger Type="Auto" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="LaunchTasks_Facilities"
                To="Facilities_Department" From="LaunchTasks"
                Classifier="NotSpecified"
                IsFork="true"
                MergeViaSetState="false"
                DisableParentStateControl="false"
                SubprocessInOutDefinition="Start"
                SubprocessStartupType="SameThread"
                SubprocessStartupParameterCopyStrategy="CopyAll">
      <Triggers>
        <Trigger Type="Auto" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="IT_Merged"
                To="Merged" From="IT_Department"
                Classifier="NotSpecified"
                IsFork="true"
                MergeViaSetState="false"
                DisableParentStateControl="false"
                SubprocessInOutDefinition="Finalize"
                SubprocessFinalizeParameterMergeStrategy="OverwriteAllNulls">
      <Triggers>
        <Trigger Type="Command" NameRef="CompleteIT" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="HR_Merged"
                To="Merged" From="HR_Department"
                Classifier="NotSpecified"
                IsFork="true"
                MergeViaSetState="false"
                DisableParentStateControl="false"
                SubprocessInOutDefinition="Finalize"
                SubprocessFinalizeParameterMergeStrategy="OverwriteAllNulls">
      <Triggers>
        <Trigger Type="Command" NameRef="CompleteHR" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="Facilities_Merged"
                To="Merged" From="Facilities_Department"
                Classifier="NotSpecified"
                IsFork="true"
                MergeViaSetState="false"
                DisableParentStateControl="false"
                SubprocessInOutDefinition="Finalize"
                SubprocessFinalizeParameterMergeStrategy="OverwriteAllNulls">
      <Triggers>
        <Trigger Type="Command" NameRef="CompleteFacilities" />
      </Triggers>
      <Conditions>
        <Condition Type="Always" />
      </Conditions>
      <Designer />
    </Transition>
    <Transition Name="Merged_Complete"
                To="Complete" From="Merged"
                Classifier="Direct" IsFork="false"
                MergeViaSetState="false"
                DisableParentStateControl="false">
      <Triggers>
        <Trigger Type="Auto" />
      </Triggers>
      <Conditions>
        <Condition Type="Action"
                   NameRef="CheckAllSubprocessesCompleted"
                   ConditionInversion="false" />
      </Conditions>
      <Designer />
    </Transition>

  </Transitions>
</Process>
```

### How the scheme works

Once the scheme is saved and `BasicPlugin` is registered with the `WorkflowRuntime`, the process runs as follows:

1. **Instance created** - the Start activity runs and the `Auto` trigger moves the process to LaunchTasks.
2. **LaunchTasks forks** - three `Auto`-triggered fork transitions (`SubprocessInOutDefinition="Start"`) create child subprocesses for IT,
HR, and Facilities. Each child runs independently and in parallel.
3. **Each subprocess waits** - IT_Department, HR_Department, and Facilities_Department each wait for their respective commands
(`CompleteIT`, `CompleteHR`, `CompleteFacilities`).
4. **Subprocess completes** - when a command is executed on a subprocess, it transitions to Merged via
`SubprocessInOutDefinition="Finalize"` and terminates.
5. **All complete** - when all three subprocesses have finalized, `CheckAllSubprocessesCompleted` returns `true` on the Merged activity. The
`Auto` trigger moves the process to Complete and it finalizes.

## Reference

BasicPlugin provides the following actions and conditions for managing subprocess lifecycles.

### CheckAllSubprocessesCompleted condition

Checks whether direct child subprocesses have finished. `Mode` controls whether child completion alone is enough or the current parent
process must also be at the merge activity. The condition uses the process instance tree maintained by the runtime.

| Parameter | Required | Default | Description |
|---|---|---|---|
| `Mode` | Yes | `AllSubprocesses` | Selects whether to wait only for direct child subprocesses or for them and the current parent process at the merge activity. |

`AllSubprocesses` waits only for direct child subprocesses. It returns `true` when the current process node in `ProcessInstancesTree` has
no active direct children.

`AllSubprocessesAndParent` waits for both parts of the merge: the direct child subprocesses must have finalized, and the current parent
process must be at the merge activity. The runtime verifies the parent part with
`processInstance.ExecutedTransition.From.Name == processInstance.CurrentActivityName`. Here, the parent is the current process that owns
the subprocess branches, not a separate ancestor process.

### DeleteSubprocesses action

Deletes all child subprocesses and their data. The action takes no parameters.

## Enums

BasicPlugin uses the following enums in condition parameters.

### CheckMode

The `Mode` parameter in `CheckAllSubprocessesCompleted` determines which processes are checked.

| Value | Behavior |
|-------|----------|
| `AllSubprocesses` | Wait until all active direct child subprocesses have finished. |
| `AllSubprocessesAndParent` | Wait until all direct child subprocesses have finalized and the current parent process has reached the merge activity. |

## See also

- [Basic Plugin Overview](https://docs.workflowengine.io/plugins/basic-plugin/overview/): Registration, configuration, and
full API reference.
- [Subprocesses](https://docs.workflowengine.io/get-started/concepts/subprocess/): How subprocesses work in Workflow
Engine.
- [Process Control](https://docs.workflowengine.io/plugins/basic-plugin/process-control/): Jump between activities and
control process state.
- [Parallel Approval](https://docs.workflowengine.io/plugins/basic-plugin/parallel-approval/): Set up multi-user approval
without explicit branches.

## Frequently asked questions

**What is the difference between subprocesses and CreateProcess?**

Subprocesses are created through fork transitions with `SubprocessInOutDefinition="Start"`. They are tracked in the process tree and
`CheckAllSubprocessesCompleted` checks them. The [CreateProcess action](https://docs.workflowengine.io/plugins/basic-plugin/process-control/#createprocess-action) creates
an independent process instance that is not tracked as a subprocess.

**How do I create parallel subprocesses?**

Add multiple fork transitions from the same activity with `IsFork="true"`, `SubprocessInOutDefinition="Start"`, and distinct target
activities. Each becomes a child subprocess.

**How do I wait for all subprocesses to complete?**

Add `CheckAllSubprocessesCompleted` as a condition on the merge transition. With `Mode="AllSubprocesses"`, it returns `true` when all
direct child subprocesses have finalized. With `Mode="AllSubprocessesAndParent"`, the current process must also be at the merge activity.

**How do I cancel subprocesses?**

Use the `DeleteSubprocesses` action to remove all child processes. Add it to an activity implementation and transition to a cancellation
state.