The CQL Continuous Query Language: Semantic Foundations and Query Execution
CQL, a Continuous Query Language, is supported by the STREAM prototype Data Stream Management System at Stanford. CQL is an expressive SQL-based declarative language for registering continuous queries against streams and updatable relations. The authors begin by presenting an abstract semantics that relies only on "Black box" mappings among streams and relations. From these mappings they define a precise and general interpretation for continuous queries. CQL is an instantiation of the abstract semantics using SQL to map from relations to relations, window specifications derived from SQL-99 to map from streams to relations, and three new operators to map from relations to streams.