A XML-Based Composite Event Model and Its Subscription Language
Jiang Ma · Chinese Journal of Computers · 2007
Content-based Pub/Sub system is gaining increasing popularity due to its loose coupling and scalable integration capability in the aspects of building large-scale software integrations.Unlike in the traditional address-based unicast or multicast,its core problem is how to match events by predicates on the contents of events.Currently,mostly existing approaches mainly limit at the “one-to-one” event matching and its matching predicates are composed of the conjunction and disjunction of non-semantic constraints.In fact,the composite event matching is required in many scenarios,typically including “one-to-many” or “many-to-one” matching.This kind of event matching enables application components to express more interest about the occurrence of complex patterns of events.A XML-based composite event model that consists of the temporal logical model and the event composite pattern is presented in the paper.The temporal logical model describes the temporal relations of events in distributed environments;the event composite pattern describes the different triggering and transferring patterns appearing the different application scenarios.Based on the composite event model,a subscription language called EXML-QL is introduced by adding the block-variables and the temporal logical operators in XML-QL language to support XML-based composite event patterns.Finally,according to the peculiarities of the subscription language,a composite event matching algorithm is presented and analyzed.