SnoopIB: Interval-based event specification and detection for active databases

Detection-based semantics does not differentiate between event detection and event occurrence and has been used for detecting events in most of the active systems that support Event–Condition–Action rules. However, this is a limitation for many applications that require interval-based semantics. In this article, we formalize the detection of Snoop (an event specification language) event operators using interval-based semantics (termed SnoopIB) in various event consumption modes. We show how events are detected using event detection graphs, and present a few representative algorithms to detect SnoopIB operators and comment on their implementation in the context of Sentinel—an active object-oriented DBMS.