Event life time in detection of sequences of events

This paper addresses the use of events within discrete-event systems modeling formalisms, presenting the concept of event life time when enclosed in the detection of a specific behavior defined by sequences of events. This concept defines the time interval during which a macro-event is valid (a macro-event is an event computed as the result of a pre-defined sequence of events). Two types of life times are defined: Absolute and Relative. Absolute life time is associated with the maximum time between the occurrence of the first and last event in the sequence. The relative life time is associated with each elementary event from the sequence and is defined by minimum and maximum values among which the next event in the sequence must occur. If the next event does not occur during the defined time, the event expires. Finally the use of these concepts is discussed presenting some specific cases of use.