Marco posted on CEP (Complex Event Processing) and GPS (Global Positioning System) recently and his examples really show the difference, to me, between event rules and decision management. He listed some great examples of rules that belong in your event processing environment - they are about events. For instance:
- Trigger when vehicle enters zone B
- Trigger when zone C contains more than 30 vehicles.
- Trigger when vehicle xyz has not arrived to zone D between 3-6 am
Event rules are not the same as the rules behind business decisions, even if the same language can be used to express both. One is tied to the events and the event handling system, one is not.
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But of course, "events" are what trigger "decisions". "Customer applies for a loan" is an event, and requires a decision on "whether and what to loan" based on current available data, current policies, and available knowledge. Saying "event rules are not the same as the rules behind business decisions" could be misunderstood to as "decisions are independent of events".
But for sure, not all event rules are decision rules. On the other hand all decision rules contain either an implicit (e.g. "loan request decision service") or explicit (e.g. "if loan request event...") event reference.
EDM's "separate the decision from the process" is perfectly correct for SOA and BPM. For EDA and event processing, where the events and associated decisions ARE the process, the mantra is possibly not so clearcut.
See my comments in : http://epthinking.blogspot.com/2008/11/on-decisions-and-event-processing.html