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12.9. Support for Event Streams
Complex event processing use cases deal with streams of events. The streams can be provided to the application via JMS queues, flat text files, database tables, raw sockets, or even web service calls.
Streams share a common set of characteristics:
- Events in the stream are ordered by timestamp. The timestamps may have different semantics for different streams, but they are always ordered internally.
- There is usually a high volume of events in the stream.
- Atomic events contained in the streams are rarely useful by themselves.
- Streams are either homogeneous (they contain a single type of event) or heterogeneous (they contain events of different types).
A stream is also known as an entry point.
Facts from one entry point, or stream, may join with facts from any other entry point in addition to facts already in working memory. Facts always remain associated with the entry point through which they entered the engine. Facts of the same type may enter the engine through several entry points, but facts that enter the engine through entry point A will never match a pattern from entry point B.
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