A computerized transaction server (1), for the conclusion of contracts between service users and service providers, comprises a user interface with several data input modules (151), having data input fields for the input of data relating to the object of the contract. Data rules and business rules, provided for the data input fields, are stored in a regulatory databank (18). The quality of inputted data values are verified by the transaction server (1), according to the provided data rules and the data values are evaluated based on the provided business rules. Various contract conclusion processes (141, 142) and/or data input modules (151) for the input of additional data are automatically selected and activated by the transaction server, depending on the result of the evaluation. For the checking and evaluation of the data values, sets of rules with differing business rules and/or data rules are selected by the transaction server (1), depending on inputted data values. The transaction server (1) permits a complex and flexibly configurable automatic evaluation or inputted data values and dynamic and automatically adjustable data input sequence and process operation plan dependent on inputted data values and stored business rules.