1. A computer program product comprising application software encoded on a tangible machine-readable information carrier, the application software being structured as process components interacting with each other through service interfaces, the software comprising: a plurality of process components, each of the process components being a package of software implementing a respective and distinct business process, the plurality of process components including: a Project Processing process component that structures, plans, and executes measures or projects; a Purchase Request Processing process component provides a request or instruction to the purchasing department to purchase specified goods or services in specified quantities within a specified time; a Purchase Order Processing process component that handles purchase orders to external suppliers and supplier confirmations; a Purchasing Contract process component that handles agreements between a purchaser and a supplier that details the supply of goods or the performance of services at agreed conditions; a Goods and Service Acknowledgement process component that handles goods and service acknowledgements, which states a recipient's obligation to pay a supplier for goods received or services rendered; a Supplier Invoice Processing process component that handles supplier invoices and supplier invoice requests; an RFQ Processing process component that handles requests for quotation and corresponding quotes; and a Time and Labor Management process component that supports the definition of employees' planned working time as well as the recording or the actual working times and absences and their evaluation; and a plurality of service interface operations, each service interface operation being implemented for a respective process component, the operations comprising inbound and outbound operations, the outbound operation for a first process component being operable to send a message to a second process component of the plurality of process components, the second process component having an inbound operation for receiving the message, the passing of messages between an inbound and an outbound operation defining a message-based pair-wise interaction between the respective process components of the respective operations, the pair-wise interactions between pairs of the process components including interactions between: the Purchase Request Processing process component and the RFQ Processing process component; the Logistics Execution Control process component and the Inbound Delivery Processing process component Inbound Delivery Processing process component; the Project Processing process component and the Purchase Request Processing process component; the RFQ Processing process component and the Purchase Order Processing process component; the Purchase Order Processing process component and the Supplier Invoice Processing process component; the Goods and Service Acknowledgement process component and the Supplier Invoice Processing process component; and the Project Processing process component and the Time and Labor Management process component.