A glue language for event stream processing

This paper describes the design and implementation of an SQL-like language for performing complex queries on event streams. The Event Stream Query Language (eSQL) aims at providing a simple, intuitive and fully non-procedural syntax, while still preserving backwards compatibility with traditional SQL. More importantly, eSQL's core syntax is designed to be extended by user-defined grammatical constrcts. These new constructs can form domain-specific sub-languages, with eSQL being used as the “glue” to form very expressive queries. These concepts have been implemented in BeepBeep 3, an open source event stream query engine.