A method and a tool for supporting transaction design in conceptual modelling of information systems is presented. The method derives automatically a transaction specification that integrates in a uniform manner the updating of base and derived information and the checking and maintenance of integrity within an information base conceptual schema. Transaction specifications thus obtained achieve their intended purpose and guarantee that information base consistency will be preserved. When there are several possible solutions, the method derives all of them. The designer may then intervene in various ways in order to select the most appropriate ones. From this choice on, the transaction processing system and the end-user can also play an interesting role in the final application of the transaction specification, for this one can be directly executable. Using a declarative, logic-based approach, the method is general, and can be adapted easily to most conceptual modelling methodologies.