When it comes to event based processing such as CEP, time becomes an important (and complicated) issue. To your average Data Analyst timelines may seem relatively simple issue – data is in the timer period of interest or not.  However when you’re dealing with events from different systems as they occur time becomes all important – the first issue that needs to be considered is, are all the systems feeding us events reporting against the same time clock. Imagine events that happen at the same time in from two different systems but a reported against different clock times would look they your event system receives them. Then how do you handle things if systems switch in and out of summer time ?  Marco Seiriö in his blog Marco on CEP provides an good explanation to some of the issues and strategies for dealing with them in his blog entry Time is an illusion. Lunchtime doubly so.

It is interesting comparing the approaches that RuleCore takes compared to those here at SeeWhy and it seems that here at SeeWhy we’ve taken the possibilities a step further by allowing the user to have policies on handling timing uses associated to each event stream.