An Abstract Semantics and Concrete Language for Continuous Queries Over Streams and Relations
Despite the recent surge of research in query processing over data streams, little attention has been devoted to defining precise semantics for continuous queries over streams. The authors first present semantics based on several building blocks: Formal definitions for streams and relations, mappings among them, and any relational query language. From these basics they define a precise interpretation for continuous queries over streams and relations. The authors then propose a concrete language, CQL (for Continuous Query Language), which instantiates the semantics using SQL as the relational query language and window specifications derived from SQL-99 to map from streams to relations.