ActiveVOS Designer User’s Guide
A BPEL process is a collection of Web services whose interactions are choreographed in a defined manner. Each service is a participant that performs some type of processing. Services can be highly granular (e.g., calculate a rate) or very large in scope (e.g., process an order).
In the example illustrated below, the process is the Seller participant, accepting a purchase order from a customer through an input message of a Web service. The Seller then places the order with the Purchasing participant. To end the process, the process returns an acknowledgement to the customer if the order could be fulfilled.
Here is a picture of the process.
After you send the acknowledgement, you could send other messages to the customer, such as shipping notices and invoices. Because you want to have this type of interaction with the customer for many purchase orders, as well as with other customers, you build one business process, and it acts as a template for business process instances.
The business process you build has a setting to "create an instance" so that each time a new purchase order arrives, you create a new process. The new process handles all the related interactions for it, keeping interactions separated for each purchase order for each buyer.
The BPEL process definition uses as input the definitions from Web Services Description Language (WSDL) files. These files contain the interface information that can be shared with the outside world. A process developer selects information, such as partner link types and operations to define the process steps, as shown in the following illustration.
A BPEL process coordinates these interactions and composes them into a straight-through or long-running flow. During execution, when exceptions occur, some activities may need reversal or undo, and a BPEL process provides the techniques for correlation, compensation, fault and event handling.
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