A data processing system (1) is programmed with objects (2) according to the object-oriented architecture. Each object (2) is for implementing an event, which for financial securities processing is often referred to as a corporate action. An object (2) has a container (3) containing a series of masks (4), all at the same level in a flat structure. Each mask has four binary bit flags, each switching on or off a pre-stored unit (5) of executable code for an asynchronous transaction. Initialization or modifications of the system involves only processing through a series of decisions and setting mask flags accordingly.