SAMOS: an Active Object-Oriented Database System.

Abstract

events are not detected by SAMOS, but users/applications have to notify the system about their occurrence by issuing an explicit raise operation. 2.2 Composite events The kinds of primitive events described above correspond to elementary occurrences and are not adequate for handling events that occur when some combination of other events happens. Thus, SAMOS supports composite events built from others by means of six event constructors. The disjunction of events (E1jE2) occurs when either E1 or E2 occurs. The conjunction of events (E1,E2) occurs when E1 and E2 occur, regardless of order. A sequence of events (E1;E2) occurs when first E1 and afterwards E2 occurs. The following three constructors monitor the occurrence of event instances of a specific event class during a predefined time interval. A composite event with the "*" -constructor (*E) will be signalled (and the corresponding rules will be executed) only once (after the first occurrence of E), even if the event E occurs sever...