In this example a company decided to diagram the Purchase Process interacting with the process performed by your suppliers.
The two processes are independent but information flows constantly via messages (phone calls, emails, etc.).
Each company needs information from the other to successfully complete the process.
The following is the diagram shows the Purchase Process example.
The Purchase department sends a Purchase Order to the Supplier.
Then, when the products are delivered, an invoice is sent to the purchase department by the Supplier.
Those interactions between processes can be represented with messages. To inset a message, click on the Message line option in the Connectors palette.
By doing the same for the send and receive invoice activities, the diagram showing collaboration will be finished.