How to Drill-Down in a BPMN Sub-Process?

Drawing a sub-process

1. Create a business process diagram, with a start event and a task Announce Proposal. Connect them with sequence flow.
   
2. You can create a sub-process by making use of the Resource Catalog. Move your mouse pointer over the task Announce Proposal.
   
3. Press on the Resource Catalog button at the top right of shape and drag it out.
   
4. Release the mouse button and select Sequence Flow > Sub-Process from the Resource Catalog.
   
5. Enter Collect Opinion as the name of the sub-process and press Enter to confirm.
   

Forming a deeper process layer

Task and sub-process are both activities in BPMN. Sub-process defers in that it lets you define finer level of process detail by mean of sub-process diagram. Let's try.

1. Click on the plus button in sub-process Collect Opinion and then select New Business Process Diagram from the popup menu.
   
   A new business process diagram is created and opened. There is a pair of start and end event. They are there for you to connect the process flow modeled in the parent diagram and the flow to be modeled in this diagram.
   
2. Let's create three tasks Receive E-mail, Give General Reply and Forward to Responsible Person in between the start and event event as shown below.
   
3. Now, go back to the upper level by clicking on the shortcut in breadcrumb.
   
4. You may optionally present the sub-process content as a preview in the sub-process shape. Click on the plus button in the sub-process Collect Opinion and then select Expand Sub-Process Preview from the popup menu.
   
   You can see the preview like the image below. If the preview is too small or too big for you, resize the sub-process shape. The preview will be updated automatically to fit the size of the sub-process shape.
   

Forming a sub-process diagram with tasks

We many group several flow objects in a business process diagram as a sub-process. Let's try.

1. Draw a new business process diagram with a start and end event, and four tasks Announce Proposal, Receive Email and Forward to Responsible Person, like this:
   
2. Select the tasks.
   
3. Right click on the selection and select Form Separate Diagram Sub-Process from the popup menu.
   
   A new sub-process diagram is formed, with the three tasks moved to there:
   
   If you have selected Form Same Diagram Sub-Process, a new sub-process shape will be created, containing the three tasks in-place, without creating any new business process diagram.