One of the benefits of organizing events into hierarchies is understanding. That brings us to another concept in CEP:
3. Different personnel need different views of the events in the enterprise, each view related to the role of the person.
For example, a CFO might want a view of the business transactions that are in progress. This knowledge may influence his financial planning. A process architect or business manager on the other hand, might want a more detailed view of the steps in each transaction and also their dependencies on lower level events in order to analyze the impact of application or middleware glitches on the running processes.
Figure 5 depicts role-oriented, real time viewing in a stock trading system. This is a highly event-driven global collaboration between multiple enterprises and individuals over various distributed IT media. Trading events, which may include anything from ticker tape messages to interest rate changes by the Fed, OPEC oil prices, etc., are processed off the messaging infrastructure. Event processing is done by a system of event processing agents (EPAs) — shown as colored boxes with arrows — distributed over the infrastructure. These contain event pattern recognition and processing rules about which we’ll say no more here. Some EPAs filter events, and others aggregate patterns of lower level events into higher level events. And other EPAs process higher level events. This gives us several levels of events derived from the cloud of stock trading events. High level events provide specialized views of the trading activity and are fed graphically to specialist role players.
One view might monitor the performance of a brokerage institution — e.g., how timely is its execution of stop loss orders. Another view might detect patterns of events indicating suspicious situations where SEC regulations such as not trading ahead on a customer’s order, may be violated. Both views use complex events, and the trick is to detect those events.
So, CEP can be used to organize the clouds of events in the infrastructures of our enterprises into hierarchies. If you don’t do that you just have a cloud of events in which you cannot see the business significance of anything. Indeed CEP is also used to create new events, like transaction views, that infer information from other events. The higher level events are complex in the sense that they are aggregated from patterns of lower level events. They contain data from the patterns that is needed to make decisions and perform various management roles. Complex in how they happen, yes. But also simpler to understand. The fact is, we deal with complex events every day of our lives.