An event-driven processing system includes: an input/output device for accepting input and displaying output data, the input/output means creating an event in response to an input by an operator; a storage device for storing a plurality of software components each having a relationship exclusively to a particular data item and activated in response to a corresponding event, the event including an abstract event corresponding to an occurrence of a particular state in the data item, in addition to the event created by the input/output means; a controller activated in response to an event for specifying a selected software component to be executed subsequently to the event according to a control program; and a processor for executing the selected software component.