The "WITHIN" statement illustrates another key concept in ESP: namely time. In this example, if the third credit_payment event isn't detected within two minutes of the first charge, the activity isn't flagged as potentially fraudulent, and the scenario completes. In stream computing, as in the "real-time, agile enterprise," the significance of any individual event - in terms of business importance - quickly depreciates. The window of opportunity to act on an event is often brief and transient. Unless the event processing architecture can rapidly discern the significance and respond, the opportunity to exploit the situation will quickly pass, with the circumstances altered by subsequent events or other factors.

Finally, we see the third key element of ESP: action. Automated systems like a credit fraud detection application often invoke event-driven actions once a pattern has been detected. In this example, the current request for a charge is declined and the account is flagged for fraud management by sending a new derived event on the ESB.

Conclusion
As the Enterprise Service Bus becomes the backbone of the enterprise IT integration infrastructure, it provides a stream of events that can make real-time insight a reality. Stream computing and the ESP tools that enable it provide the ability to detect time, cause, and spatial-based patterns among events in the ESB stream. By combining ESP rules with an ESB-normalized integration fabric, the enterprise can become truly agile.

References

• Event Programming:
  Mark Palmer and Gareth Smith.
  "An Event Processing Language Tutorial." Progress Software.
• General ESP Product and Academic Information:
  A is a web portal of ESP term definitions, links to ESP products, academic papers, and community discussions.
  www.eventstreamprocessing.com
• ESP Architecture and Technology:
  John Bates.
  "Apama Technical Overview." Progress Software. Available on request.
  Mark Palmer.
  "Event Stream Processing, a New Physics of Computing." DMReview. July, 2005.
  www.dmreview.com
• Glossary of Terms:
  A glossary of industry terms, including BAM, CEP, EDA, Event, and Event Streams can be found at www.eventstreamprocessing.com/glossary
• Community and Discussion Group:
  The CEP-interest group, co-moderated by Mark Palmer and David Luckham, has been joined by enterprise architects, members of academia, software vendors, and industry analysts interested in ESP and CEP.
  http://groups.yahoo.com/group/CEP-Interest.
• Radio Frequency Identification (RFID) and ESP:
  Mark Palmer.
  "The 7 Principles of RFID Data Management."
  www.esj.com/enterprise/article.aspx?EditorialsID=1076
• Algorithmic Trading and ESP:
  Dr. John Bates. "The Apama Technical Overview." 2005.
• Complex Event Processing:
  David Luckham. "The Power of Events, An Introduction to Complex Event Processing in Distributed Enterprise Systems." Indianapolis. 2002. A comprehensive list of academic papers and resources can be found at www.eventstreamprocessing.com/webindex.htm.
• Academic Resources on complex event processing, data stream processing:
  The event-stream processing resource site is at www.eventstreamprocessing.com
  See the index.