1. A computer program product embodied in a computer readable storage medium for construction of rules for use in a complex event processing application program, the computer program product comprising the programming instructions for: providing a rule construction interface for constructing rules for a rule set of a complex event processing system, said rules comprising definitions of one or more detected events and corresponding actions, said interface being arranged to enable a user definition of new events or actions during a rule construction process; in response to an identification of a new event or action during said rule construction process via said rule construction interface, generating a corresponding event or action logical construct for representing said event or action in said complex event processing system; generating an intermediate logical construct arranged to provide a data connection for said event or action logical construct; and linking said event or action logical construct to a corresponding action or event logical construct via said intermediate logical construct.