1. A computer-implemented method of event processing, said method comprising: providing an event processing pattern language operative to be implemented and executed on a system having at least a computer processor; first extending said event processing pattern language to support historical patterns thereby enabling a user to define patterns comprised of both on-line streaming and retrospective historical patterns utilizing a single pattern language, wherein said historical patterns include a time window determined in an event-driven manner open from the present time backwards thereby providing pattern detection for both on-line streaming events and historical events; second extending said event processing pattern language with a primary and secondary context pattern language extension for looking backwards in time on past events while simultaneously handling time advancing forward in on-line streaming events thereby enabling both primary and secondary context pattern languages to be written in the single pattern language; wherein said first and second extending extend said event processing language to retrospective processing functions and enable the retrospective processing functions to be mapped into logical event processing agents (EPAs); and wherein said steps of providing, first extending and second extending are implemented in either of computer hardware configured to perform said providing and extending steps, and computer software embodied in a non-transitory, tangible, computer-readable storage medium.