title: The CQL Continuous Query Language: Semantic Foundations and Query Execution
creator: Arasu, Arvind
creator: Babu, Shivnath
creator: Widom, Jennifer
subject: Data Streams
subject: Miscellaneous
description: 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.  We begin by presenting an abstract semantics that relies only on ``black box'' mappings among streams and relations.  From these mappings we define a precise and general interpretation for continuous queries.  CQL is an instantiation of our 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.  Most of the CQL language is operational in the STREAM system.  We present the structure of CQL's query execution plans as well as details of the most important components: operators, inter-operator queues, synopses, and sharing of components among multiple operators and queries.  Examples throughout the paper are drawn from the Linear Road benchmark recently proposed for Data Stream Management Systems.  We also curate a public repository of data stream applications that includes a wide variety of queries expressed in CQL.
publisher: Stanford
date: 2003
type: Techreport
type: NonPeerReviewed
format: application/pdf
identifier: http://ilpubs.stanford.edu:8090/758/1/2003-67.pdf
identifier: Arasu, Arvind and Babu, Shivnath and Widom, Jennifer (2003) The CQL Continuous Query Language: Semantic Foundations and Query Execution. Technical Report. Stanford.
relation: http://ilpubs.stanford.edu:8090/758/