Some CEPs even have query languages which look very like SQL (Esper [1]). But... it's different: 1) it's push model vs pull in database (you toss data in meatgr

Some CEPs even have query languages which look very like SQL (Esper [1]). But... it's different: 1) it's push model vs pull in database (you toss data in meatgrinder and see outcome on other side as stuff goes in vs going to data and picking what you need); 2) CEPs usually keep track of data only in specified windows (time/distance); you explicitly have to manage manual data windows; this means queries to join everything with everything between two data streams will result in memory explosion on large data sets; 3) CEPs trigger evaluation on message inserts/removals - this means you can't trigger re-evaluation at will without any stimulus event and you can't do joins with absence of something; you can't simply ask CEP to fire an event if no new events happened in last 5 minutes - that needs some query trickery. [1] http://www.espertech.com/products/esper.php http://www.espertech.com/products/esper.php