Evolution and reactivity in the semantic web
Semantic techniques for the web
User-oriented rule management for event-based applications
Proceedings of the 5th ACM international conference on Distributed event-based system
Run-time composite event recognition
Proceedings of the 6th ACM International Conference on Distributed Event-Based Systems
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Web systems, Web services, and Web-based publish/subscribe systems communicate events as XML messages and in many cases, require composite event detection: it is not sufficient to react to single event messages, but events have to be considered in relation to other events that are received over time. This entails a need for expressive, high-level languages for querying composite events. Emphasizing language design and formal semantics, we describe the rule-based composite event query language XChangeEQ. XChangeEQ is designed to completely cover and integrate the four complementary querying dimensions: event data, event composition, temporal relationships, and event accumulation. Semantics are provided as a model theory with accompanying fixpoint theory, an approach that is established for rule languages but has not been applied to event queries so far. Because they are highly declarative, thus easy to understand and well suited for query optimization, such semantics are desirable for event queries.