1. A computer readable medium including program code for providing message-based services using a service-oriented methodology for implementing an instance of a deployment unit, the medium comprising: program code for storing an instance of a purchasing deployment unit for the integrated management of the operational purchasing life cycle, covering activities to control and centrally manage purchase requests, manage contracts, perform purchase order collaboration, and confirm goods and services, where the purchasing deployment unit defines the limits of an application-defined transaction for the integrated management of the operational purchasing life cycle, covering activities to control and centrally manage purchase requests, manage contracts, perform purchase order collaboration, and confirm goods and services by a set of actions that have atomicity, consistency, isolation, and durability in a database, and wherein the actions associated with the application-defined transaction are performed by one or more process components contained in the purchasing deployment unit, wherein each process component comprises a software package realizing a business process and exposing its functionality as one or more service operations, wherein the purchasing deployment unit comprises: a purchase order processing process component, wherein the purchase order processing process component implements the following service operations: a request purchase order cancellation operation, a change purchase order based on invoice values operation, a create purchase order confirmation operation, a change purchase order based on inbound delivery request operation, a notify of invoicing due operation, a change purchase order based on delivery values operation, a create purchase order based on winning quote operation, a notify of purchase order operation, a request purchase order change operation, a notify of expected delivery operation, a notify of purchase order operation, a request purchase order creation operation, a notify of purchase order operation, a create purchase order operation, and a request supplier invoice request migration operation; a purchase request processing process component, wherein the purchase request processing process component implements the following service operations: a change purchase request based on RFQ execution operation, a request RFQ execution operation, a confirm purchase request operation, a notify of purchase request operation, and a maintain purchase request operation; a purchasing contract processing process component, wherein the purchasing contract processing process component implements the following service operations: a change purchasing contract based on RFQ execution operation, a confirm purchasing contract operation, a maintain purchasing contract operation, a notify of product catalog operation, a notify of project task assignment operation, a notify of purchasing contract operation, a request project task accountability information operation, a request RFQ execution cancellation operation, a request RFQ execution operation, a maintain purchasing contract release operation, a create purchasing contract operation, a notify of invoicing due operation, and a notify of purchase schedule agreement operation; a goods and service acknowledgement process component, wherein the goods and service acknowledgement process component implements the following service operations: a create goods and service acknowledgement operation, a create goods and service acknowledgement operation, a confirm goods and service acknowledgement operation, a notify of invoicing due operation, a notify of goods and service acknowledgement operation, a notify of goods and service acknowledgement operation, a notify of goods and service acknowledgement cancellation operation, and a cancel goods and service acknowledgement operation; and wherein the process components of the purchasing deployment unit are packaged together to be deployed on a single computer system; and program code for executing the application-defined transaction for integrating management of the operational purchasing life cycle, covering activities to control and centrally manage purchase requests, manage contracts, perform purchase order collaboration, and confirm goods and services; and program code for presenting data associated with the executed application-defined transaction for integrating management of the operational purchasing life cycle, covering activities to control and centrally manage purchase requests, manage contracts, perform purchase order collaboration, and confirm goods and services to a graphical user interface.