A transaction control system (1) generates presentation objects (19-22) which reside on front-end terminals. The control system (1) also comprises a business rules layer (16), a transaction layer (17), and an external interface layer (18). A transaction processing module (M1-M4) is created by a control system generating a presentation object and transferring it to a relevant front-end terminal and also instantiating a business object (23-25), a transaction object (27-29), and an external interface object (30-32). Development of transaction processing modules is therefore very simple and the module is versatile and may be easily modified.