Core System Pieces

The system's core pieces are the PurchaseOrder interface and the Inventory interface.

• The PurchaseOrder interface is defined using a WSDL document and has one operation called sendPurchaseOrder. The PurchaseOrder interface is implemented using one BPEL process exposed through SOAP over HTTP. That means that anyone who can send a SOAP message over HTTP to this service can make a purchase.

• The Inventory interface is defined using a WSDL document and has one operation called isInventoryAvailable. The Inventory interface is implemented using another BPEL process, invoked by the PurchaseOrder service, to determine whether there is sufficient inventory of each book to complete a purchase order. This service is also exposed through SOAP over HTTP. Anyone can make a call to this service, but the main caller of this service is the PurchaseOrder service.