This article includes a list of general references, but it lacks sufficient corresponding inline citations. Please help to improve this article by introducing more precise citations. (March 2015) (Learn how and when to remove this message)

Esper is an open-source Java-based software product for Complex event processing (CEP) and Event stream processing (ESP), that analyzes series of events for deriving conclusions from them.

Esper extends the SQL-92 standard for its engine and enterprise framework, providing Aggregate function, Pattern matching, event windowing and joining. Esper implements Event-driven programming and event-driven architecture.

Esper was created in 2006 by EsperTech Inc. It offers a Domain-specific language for processing events called Event Processing Language (EPL). EPL is a Declarative programming language for analyzing time-based event data and detecting situations as they occur.

Esper is a Java-based application but has been ported to the C# programming language and is available for the .NET Framework under the name NEsper.

EsperTech Inc. provides Esper Enterprise Edition^[1] with enterprise-ability features.

This example^[2] illustrates a simple EPL query that outputs a row immediately when within a sliding window of 3 minutes the number of order events reaches 5 or more events.

select count(*) from OrderEvent#time(3 min) having count(*) >= 5

• Rapide (Stanford)
• StreamSQL: StreamSQL is a query language that extends SQL with the ability to process real-time data streams.

• Complex event processing (CEP) - A related technology for building and managing event-driven information systems.
• Data Stream Management System (DSMS) - A type of software system for managing and querying data streams
• Event correlation
• Event-driven architecture — (EDA) is a software architecture pattern promoting the production, detection, consumption of, and reaction to events.
• Event stream processing — (ESP) is a related technology that focuses on processing streams of related data.
• Operational intelligence — Both CEP and ESP are technologies that underpin operational intelligence.
• Pattern matching
• Real-time business intelligence — Business Intelligence is the application of knowledge derived from CEP systems
• Real-time computing — CEP systems are typically real-time systems
• Real time enterprise

• Esper Official Website
• EsperTech Inc.
• Research Papers referencing Esper, by Google Scholar
• Analysis of Complex Event Processing with Esper by Eric Miller, a book on Esper and CEP.
• Event Processing in Action by Opher Etzion and Peter Niblett, Manning Publications (ISBN 9781935182214), a book that provides Esper examples
• Open Source SOA by Jeff Davis, Manning Publications (ISBN 1933988541), a book that provides examples of Esper for monitoring web services
• OSWorkflow: A guide for Java developers and architects to integrating open-source Business Process Management, by Diego Adrian Naya Lazo, PACKT (ISBN 978-1847191526 ), a book with a chapter on Esper
• Fraunhofer CEP Market Overview, by Fraunhofer, year 2010
• Forrester Wave for Complex Event Processing, by Forrester - Oct. '09
• Real-Time Stream Processing as Game Changer in a Big Data World with Hadoop and Data Warehouse, InfoQ - Sept. '14