https://www.igvita.com/2011/05/27/streamsql-event-processing-with-esper/

http://torycatkin.iteye.com/blog/1343596

http://blog.csdn.net/yixuan_1/article/category/1908125

http://blog.csdn.net/xiaohulunb/article/details/38538815

http://docs.fluentd.org/articles/cep-norikra

http://esper.codehaus.org/tutorials/solution_patterns/solution_patterns.html#aggregate-0

Esper