Technically, BPM/Business Rules approach place process logic with the BPM suite and decision logic in the business rules management system (BRMS). The process logic in a BPM suite sequences and controls activities and launches and cancels processes. Control is achieved with timers and exception handlers. Processes can be designed to recover from errors, restart processes and coordinate activities. The BRMS effectively designs, organizes and executes the logic behind a process decision. An effective BRMS can handle any depth and complexity of decision logic, including computationally complex logic and dense logic.
Bruce makes an interesting comment on business rules too: that “routing logic in process gateways” are not “business rules”. That doesn’t really make sense: for sure some gateways will be process-housekeeping decisions of little interest to the business user, but others will surely embed business-critical decisions. On the other hand, it has long been acknowledged that a best practice for BPM is to delegate such business decisions to a managed decision service - hence the explicit new business rule (aka decision) task in BPMN 2.0. And,in the CEP world, for tools like TIBCO BusinessEvents to invoke a decision managed by its Decision Manager tool.
CEP module receives or intercepts a flurry of events and processes them with the objective of figuring out what those events are relevant for; it triggers the appropriate business processes or decision services
BPM module receives the request for a given process to be applied to a higher level entity (an application, a document...); it automates the steps defined in the business process
BRMS module is invoked with a given context to apply business rules; it makes a business decision