It is not uncommon to hear some disagreements among advocates of Business Rules, Complex Event Processing or CEP, Business Process Management as to exactly what the overlap between these products might be. Tim Bass fired the latest broadside with CEP is Not BPM, BAM, BRE, BRMS or SOA.
Tim goes through some examples, arguing one is simply BPM while the other is really CEP and, while I agree with the thrust of his argument, I do need to take issue a little. Part of the problem comes from the very utility of "business rules". Clearly business rules are valuable in BPM for specifying order routing. Equally clearly, as the folk at Tibco's CEP blog have been discussing, business rules are an important part of CEP, a way of specifying how events are correlated and processed. Trying to compare two things (BPM and CEP) that should use business rules to business rules themselves is a little tricky and, I think, causes more problems than it is worth.
This is why I talk more and more about decision management not about business rules. in the first example, order routing, we either make a true business decision or we do not. If we don't - if the routing is tightly coupled to the process - then this is an example of rules-based routing in a process. If a complex decision that has nothing to do with the process (such as the availability of credit or the profitability of a customer) then the rules-based routing is relying on a managed decision . Similarly, in Fraud, there is a decision to be made (is this a fraudulent transaction) that is independent of the system/process/event that is asking. This decision might use rules as well as analytics but it is still a decision that should be managed. If I want to do this in an event-based way, rather than a batch way, then this decision becomes part of and must be integrated with my event processing environment. Complex Event Decisioning, if you like.
As Tim says, event correlation and analysis is what makes something CEP and CEP is intensely complementary to decision management. Business rules are good for both (and indeed for much more) and should be part of how you address both.
Here are some other posts on this topic: