Database Reference
In-Depth Information
Figure 4.4.
An Execution Plan for Query Q4.
The work in [43] tries to to improve the eciency of complex RFID
event detection with SASE framework where the domains of event at-
tributes (e.g. tag ID) are quasi-infinite. Methods proposed include a
delay matching method based on selectivity of injected events and two
sliding window strategies based on time-slot and B+ tree. As an ex-
tension of SASE, SASE+ [70] employs an optimization strategy based
on pattern match buffer sharing to support sharing among intermediate
results, thus reduces the maintenance cost of intermediate results.
In RCEDA, to process RFID rules, the events from the rules are
first constructed into an event graph, and then the event graph will be
initialized as follows: i) propagate interval constraints in a top-down way;
ii) assign event detection modes bottom-up based on event constructors
and interval constraints; and assign pseudo event generation flags top-
down based on the event detection modes. When pseudo events are
created, they are placed in a sorted pseudo event queue based on their
scheduled execution timestamps. The incoming RFID event queue is
ordered based on observation timestamps. When the event is processed,
the event engine fetches the earliest event from the two queues.
4. Advanced Topics on Complex Event
Processing for Sensor Streams
In real world problems, complex event processing faces more chal-
lenges, such as the effect of event uncertainty and the disorder of events.
