Glossary of Terms

Event Anything that happens or is contemplated as happening.


  • A financial trade
  • An airplane lands
  • A sensor outputs a reading
  • A change of state in a database or a finite state machine
  • A keystroke
  • A natural occurrence such as an earthquake
  • A social or historical happening (e.g., the abolition of slavery, the battle of Waterloo, the Russian Revolution, and the Irish potato famine).

Event (event object, event message, event tuple) An object that represents, encodes, or records an event, generally for the purpose of computer processing.


  • A purchase order (records a purchase activity)
  • An email confirmation of an airline reservation
  • Stock tick message that reports a stock trade
  • A message that reports an RFID sensor reading
  • A medical insurance claim document


1. Events are processed by computer systems by processing their representations as event objects. The same activity may be represented by more than one event object; each event object might record different attributes of the activity. In many event processing systems, for example simulation systems, events are immutable. In such systems, a modification or transformation of an event must be achieved by creating a new event object and not by altering the original event. Deletion would entail removing an event from further processing.

2. Overloading: Event objects contain data. The word—event is overloaded so that it can be used as a synonym for event object. In discussing event processing, ...

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