The Workflow system consists of components installed on your Application Object Server (AOS) and components installed on a Web server. The following diagram illustrates how these servers communicate with each other.

To better understand how the Workflow components on these two servers communicate, consider the following example. Assume that an employee creates a purchase requisition and submits it for processing and approval. The following events occur:

1. When the user submits the purchase requisition, a workflow activation message is saved to a message queue in the Microsoft Dynamics AX database.

2. The message processing batch retrieves messages from the queue and sends them to the Workflow Web server for processing.

3. The Workflow Web services, located on the Workflow Web server, receive the messages. The messages are then sent to Windows Workflow Foundation.

4. Windows Workflow Foundation processes the messages and completes the following work:

   • Executes the next step in the workflow.

   • Determines who is assigned to each task and document.

   • Calculates due dates for each task and document.

5. The .NET Business Connector sends the messages back to the AOS server.

6. The due date expirations batch processes each overdue task and document.