1. A computer program product comprising application software encoded on a non-transitory, 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 comprising a modular and application-independent package of reusable software implementing a respective and distinct business process, the business process comprising functionality exposed by the process component via at least one service interface, the plurality of process components including: a due item processing process component that collects, manages, and monitors trade receivables or payables and corresponding sales tax or withholding tax; a project processing process component that structures, plans, and executes simple, short-term measures and complex projects; a balance of foreign payment management process component that collects, processes, and reports receivables and payables according to foreign trade regulations to create a balance of payments of a country; a payment processing process component that processes and manages payments and conducts communications with financial institutions; a customer invoice processing process component that processes invoicing of customers for delivery of goods or provision of services; and an accounting process component that processes business transactions for valuation and profitability analysis; and a plurality of service interfaces, each service interface associated with exactly one process component and comprising at least one operation, each operation being implemented for exactly one 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 due item processing process component and a due item processing at business partner process component; an accounting coding block distribution processing process component and the project processing process component, where the pair-wise interaction between the accounting coding block distribution processing process component and the project processing process component includes the transmission of: an accounting object check request message from the accounting coding block distribution processing process component to the project processing process component the accounting object check request message requesting a status check for tasks associated with the existence and availability for expense or resource assignment in accounting; and an accounting object check confirmation message from the project processing process component to the accounting coding block distribution processing process component the accounting object check confirmation message providing a confirmation of the existence of at least one accounting object and whether the at least one accounting object is permitted for assignment in accounting; the payment processing process component and the due item processing process component, where the pair-wise interaction between the payment processing process component and the due item processing process component includes the transmission of: a clearing request message from the payment processing process component to the due item processing process component, the clearing request message requesting the clearing of payments within the due item processing process component; a clearing cancellation request message from the payment processing process component to the due item processing process component, the clearing cancellation request message requesting cancellation of a previously sent clearing request; and a clearing confirmation message from the due item processing process component to the payment processing process component, the clearing confirmation message providing a confirmation or rejection to the payment processing process component in response to a clearing request or clearing cancellation request message; the customer invoice processing process component and the accounting process component, where the pair-wise interaction between the customer invoice processing process component and the accounting process component includes the transmission of: an invoice accounting notification message from the customer invoice processing process component to the accounting process component, the invoice accounting notification message requesting the accounting process component to create an accounting document based on invoice data received from the customer invoice processing process component; an invoice cancellation accounting notification message from the customer invoice processing process component to the accounting process component, the invoice cancellation accounting notification message requesting the accounting process component to cancel an existing accounting document based on cancellation data received from the customer invoice processing process component; and a sales and purchasing accounting notification message from the customer invoice processing process component to the accounting process component, the sales and purchasing accounting notification message notifying the accounting process component about the creation, change, or cancellation of a customer invoice request; a bank statement creation at bank process component and the payment processing process component; the due item processing process component and the customer invoice processing process component, where the pair-wise interaction between the due item processing process component and the customer invoice processing process component includes the transmission of: a due clearing notification message from the due item processing process component to the customer invoice processing process component, the due clearing notification message notifying the customer invoice processing process component about clearing of trade receivables at the due item processing process component; the customer invoice processing process component and the balance of foreign payment management process component, where the pair-wise interaction between the customer invoice processing process component and the balance of foreign payment management process component includes the transmission of: a foreign receivable payable notification message from the customer invoice processing process component and the balance of foreign payment management process component, the foreign receivable payable notification message notifying the balance of foreign payment management process component about an invoice in order to track a receivable from or a payable to a non-resident business partner; and a foreign receivable payable cancellation notification message from the customer invoice processing process component and the balance of foreign payment management process component, the foreign receivable payable cancellation notification message notifying the balance of foreign payment management process component about the cancellation of a previously posted supplier invoice; the payment processing process component and a payment processing at business partner process component; the payment processing process component and a payment order processing at house bank process component; and the customer invoice processing process component and a supplier invoice processing at customer process component.