An XML Framework for Integrating Continuous Queries, Composite Event Detection, and Database Condition Monitoring for Multiple Data Streams

Abstract

With advancements in technology over the last ten years, data management 
issues have evolved from a stored persistent form to also include streaming 
data generated from sensors and other software monitoring tools. 
Furthermore, distributed, event-based systems are becoming more prevalent,
with a need to develop applications that can dynamically respond to information extracted from data streams. This research is investigating the
integration of stream processing and event processing techniques, with
expressive filtering capabilities that include queries over persistent databases
to provide application context to the filtering process. Distributed Event 
Processing Agents (DEPAs) continuously filter events from multiple data 
streams of different formats that provide XML views. Composite events for 
data streams are expressed using the Composite Event Detection Language (CEDL) and mapped to Composite XQuery (CXQ) for implementation. CXQ is a language that extends XQuery with features from CEDL, including operators for expressing sequence, disjunction, conjunction, repetition, aggregation, and time windows for events. Continuous queries and composite event filters are integrated with techniques for materialized view maintenance and 
incremental evaluation in condition monitoring to provide efficient ways of 
enhancing stream filters with database queries. The filtering and event 
detection load is distributed among multiple DEPAs, with CXQ expressions 
decomposed to allocate subcomponents of the expression to DEPAs that 
efficiently communicate in the global detection of  composite events. A unique 
aspect of our research is that it extends XQuery with temporal, composite 
event  features to combine techniques for continuous queries in stream 
processing, incremental evaluation in condition monitoring, and detection and 
filtering of composite events, creating an expressive environment for the 
extraction of meaningful events from multiple data streams with XML views.