Call Activity

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1. Overview

Call Activity is a standard BPMN-modeling element supported by Camunda Engine. It allows you to call another process as part of the currently running process. Call Activity is similar to embedded subprocess, but is external, meaning it’s modeled within a separate business process pool, and can be used multiple times by different Parent[1] business processes.

bp call activity 01

In Camunda BPM the calling of global (external) subprocess can be executed between processes modeled in separate .bpmn files, or within a single .bpmn file. This way an independent business process can start another one, and vice versa.

The registry platform currently supports only one type — calling a global subprocess from a Parent process. From a global subprocess you can execute the Call Activity — a subprocess of the 2nd level (see Restricting nesting levels when calling subprocesses with Call Activity).

Example. Calling between processes, modeled in separate BPMN files

call activity separate bpmn

Example. Calling between processes, modeled in one BPMN file.

call activity same bpmn

When a Call Activity element is brought into action, a new instance is created for the process the element is linked to. The new instance is activated during none-start[2] event. The process can have start events of other types, but they are ignored.

When the created instance is ended, the call action is stopped, and the sequence flow continues.

In other words, when Call Activity is executed, the process that initiated the call awaits the end of the global subprocess, and continues after that.

2. Types of Call Activity element template extensions

To simplify business process modeling within the registry Platform, a number of extension (delegate) types that are configured using the developed Call Activity element templates, were implemented:

  1. Call Activity — general template for global subprocess call.

  2. Check excerpt status — specialized template for the calling of check excerpt status subprocess.

We differentiate Call Activity as a BPMN element and Call Activity as this element’s extension that is configured using the callActivity.json developed template, used to call the global subprocess.

3. Modeling business processes using Call Activity extensions

Let’s look at the application of Call Activity BPMN-element using callActivity.json developed template-extension to call global subprocesses on the example of online order processing business processes (further in the text — main or parent process) and confirmation of the order (further in the text — subprocess).

bp call activity 1

On the modeling stage it is required to create 2 business process pools and save them within one .bpmn file.

3.1. Process modeling stages

To model 2 processes (the parent process and the global subprocess in our case) using Call Activity, we need to go through the following stages:

  1. Creating parent process pool.

  2. Modeling start event of the parent process.

  3. modeling the user task for entering online order data.

  4. modeling Call Activity to call external subprocess.

  5. Creating a pool for the global subprocess.

  6. modeling the user task for order payment.

  7. Modeling main process end event.

3.2. Creating parent process pool

To model a pool for the parent process, take the following steps:

Parent process pool modeling must be performed within the Create Pool/Participant element.

  1. Open Camunda Modeler and create a new BPMN diagram by clicking File menu > New File > BPMN Diagram.

    bp 1

  2. On the left panel, find Create pool/Participant and drag it onto the modeling canvas.

    bp 2

  3. Fill in the fields with the corresponding values:

    • In the Participant Name field, enter the name for the pool — Creating an order on the website.

    • In the Process id enter business process ID — create-order.

    • In the Process Name field enter process name — Creating an order on the website.

    bp call activity 2

3.3. Modeling start event of the parent process

To model a start event, take the following steps:

  1. On the left panel, find the CreateStartEvent and drag it onto the modeling canvas.

  2. On the right panel, fill in the following parameters with the corresponding values:

    • In the Name field, enter the name for the start event — Cart;

    • In the Initiator field, enter initiator.

    initiator — is a special variable set for the user who started the process.

    + bp call activity 3

3.4. modeling the user task for entering online order data

To create a user task for data entering, take the following steps:

  1. Create a new task, define its type by clicking the key icon and selecting User Task from the menu.

  2. On the right panel, click Open Catalog, select User Form template, and click Apply to confirm.

  3. On the right panel, fill in the following fields:

    • In the Id field, set task ID — user-form-1.

      Task ID is automatically set by default. Enter it manually if required.

    • In the Name field, enter task name — Order data form.

    • In the Form key field, enter form key that will correspond with the form service name — add-order-bp-add-order-test.

    • In the Assignee field, enter the variable of the user who initiated the process instance — ${initiator}.

    bp call activity 4

3.5. modeling Call Activity to call external subprocess

To model Call Activity, take the following steps:

You can find an example of Call Activity delegate configuration here.

  1. Create the Call Activity element.

  2. Perform the following configurations:

    • In the Name field, enter element name — Decision on order confirmation.

    • In the Called Element field, set the ID of the global subprocess to be called — order-confirm.

    • In the Input data field, set the input data to be sent to the called business process. The parameters must be transferred in the form of key-value pairs (here — ${submission('user-form-1').formData}).

      You can find more detauls on using the submission() function on the following page: JUEL functions in business processes.

    • In the Output variable name set the payload-carrying variable name (here — callActivityOutput).

    bp call activity 5

This way the current configuration starts a global subprocess from the main pool. The main process can’t end while the global subprocess is running.

3.6. Creating a pool for the global subprocess

Model a pool for the global subprocess as shown in the example Creating parent process pool.

  1. On the left panel, find the Create pool/Participant element and drag it to the modeling canvas.

    bp 2

  2. Fill in the following fields with the corresponding values:

    • In the Participant Name field, enter the name of the pool displayed in the modeler — Decision on order confirmation.

    • In the Process id field, enter business process ID — order-confirm.

    • In the Process Name field, enter business process name — Decision on order confirmation.

    bp call activity 6

3.7. Modeling start event for the global subprocess

Model a start event for the global subprocess as shown in the example Modeling start event of the parent process.

To do that, take the following steps:

  1. On the left panel, find the CreateStartEvent element and drag it to the modeling canvas.

  2. On the right panel, fill in the following parameters with the corresponding values:

    • In the Name field, enter the name of the start event — Receiving order data.

    • In the Initiator field, enter initiator.

      initiator — is a special variable set for the user who started the process.

    bp call activity 7

3.8. Modeling the "Decision for order confirmation" user task

Create the "Decision for order confirmation" user task based on the example modeling the user task for entering online order data, by taking the following steps:

  1. Create a new task, define its type by clicking the key icon and selecting User Task from the menu.

  2. On the right panel, click Open Catalog, select User Form template, and click Apply to confirm.

  3. On the right panel, fill in the following fields:

    • In the Id field, enter task ID — user-form-2.

      Task ID is automatically set by default. Enter it manually if required.

    • In the Name field, enter task name — Decision for order confirmation.

    • In the Form key field, enter a form key that will correspond with the form service name — add-order-bp-order-confirm-test.

    • In the Assignee field, enter the variable of the user who initiated the process instance — ${initiator}.

      bp call activity 8

3.9. Modeling the script task to prepare the data for output

Create a script task for data processing and preparation for output.

The task purpose is to take the data that the user filled in the form, using groovy-script with submission() function, form an output in JSON format, and write it into callActivityOutput variable, defined in Output variable name field when modeling Call Activity of the main process.

  1. Create a new task, define its type by clicking the key icon and selecting Script Task from the menu.

  2. On the right panel, fill in the following fields:

    • In the Name field, enter task name — Preparing data for output

    • In the Script Format field, enter script format — groovy.

    • In the Script Type field, enter script type — Inline Script.

    • In the Script field, enter the groovy-script:

      var data = submission('user-form-2').formData
execution.removeVariable('outputPayload')
set_transient_variable('outputPayload', S(data, 'application/json'))

    bp call activity 9

3.10. modeling global subprocess end event

  1. Create a business process end event.

  2. On the right panel, set the Name parameter to Order confirmed.

    bp call activity 10

The data received as a result of the "Decision for order confirmation" global subprocess execution are written into the callActivityOutput variable, defined in the Output variable name field when modeling Call Activity of the main process, and can be used on the order payment form in the main process. After that, the main process execution continues.

3.11. modeling the user task for order payment

Create the user task for order payment based on the example modeling the user task for entering online order data, by taking the following steps:

  1. Create a new task, define its type by clicking the key icon and selecting User Task from the menu.

  2. On the right panel, click Open Catalog, select User Form template, and click Apply to confirm.

  3. On the right panel, fill in the following fields:

    • In the Name field, enter task name — Order payment.

    • In the Form key field, enter form key that will correspond with the form service name — add-order-bp-view-order-test.

    • In the Assignee field, enter the variable of the user who initiated the process instance — ${initiator}.

    bp call activity 11

3.12. Modeling main process end event

  1. Create the business process end event.

  2. On the right panel, fill in Name parameter with Order paid.

    bp call activity 12

4. Restricting nesting levels when calling subprocesses with Call Activity

The Platform has certain restrictions on how many nesting levels are allowed for business processes during the calling of global subprocesses with Call Activity.

For proper calling of global subprocesses with Call Activity functionality operation, use no more than 3 nesting levels for bysiness processes. This means the main process, global subprocess of the 1st level, and global subprocess of the 2nd level.

5. Displaying business processes in user Portals

Users of Officer and Citizen Portals will see only the names of parent business processes of the highest level on My services and My tasks pages during the execution of called or in-built subprocesses.

If business process A called subprocess B, and subprocess B called subprocess C, the user will only see business process A name in the Portal.

1. Parent Process is a process that initiates subprocess start. A subprocess is a Child Process to a Parent Process.
2. None events are undefined events, also called "empty."