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.
The main characteristic to be aware of in these tools is that BE is primarily rule-based (using an embedded rule engine), whereas BW and iProcess are orchestration / flow engines. In BE we can use a state diagram to indicate a sequence of states which may define what process / rules apply, but this is really just another way of specifying a particular type of rules (i.e. state transition rules).
The main advantages to specifying behavior as declarative rules are:
Handling complex, event-driven behavior and choreography
Iterative development, rule-by-rule
The main advantages of flow diagrams and BPMN-type models are:
Ease of understanding (especially for simpler process routes)
Process paths are pre-determined and therefore deemed guaranteeable.
In combination these tools provide many of the IT capabilities required in an organization. For example, a business automation task uses BW to consolidate information from multiple existing sources, with human business processes for tasks such as process exceptions managed by iProcess. BE is used to consolidate (complex) events from systems to provide business information, or feed into or drive both BW and iProcess, and also monitors end-to-end system and case performance.
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JT has posted his view on rules and decisions and how they relate. Given that James talks more about services than events, I thought it would be worth reviewing his post from both a Complex Event Processing and a TIBCO BusinessEvents event processing platform perspective.
”Decision Services:
Support business processes by making the business decisions that allow a process to continue.
Support event processing systems by adding business decisions to event correlation decisions (they are often called Decision Agents in this context).
Allow crucial and high-maintenance parts of legacy enterprise applications to be externalized for reuse and agility.
Can be plugged into a variety of systems using Enterprise Service Bus approaches.”
- leave anything related to transport, communication to other layers- use this revised CEP to express and execute event-relevant logic, the purpose of which is to translate the ambient events into relevant business events- have these business events trigger business processes (however lightweight you want to make them)- have these business processes invoke decision services implemented through decision management to decide what they should be doing at every step- have the business processes invoke action services to execute the actions decided by the decision services- all the while generating business events or ambient events- etc.
Rule-processing is just a style of computation. Of course it is used in BRMS, but it is also used in CEP. CEP systems typically employ rules-based processing to infer higher-order events by matching patterns across many event streams within the event ‘cloud’. BRMS’s use rule processing to match patterns within data tuples representing business-orientated data. CEP systems may support the use of advanced analytics to manage predictive analysis, reasoning under uncertainty and other requirements in relation to the event cloud. Some of the better BRMS’s offer similar analytics in regard to processing business data.
Most BREs today are deployed as “decision services”, and are used in “stateless” transactions to make “decisions” as a part of a business process. A CEP application is instead processing multiple event streams and sources over time, which requires a “stateful” rule service optimized for long running. This is an important distinction, as a stateful BRE for long-running processes needs to have failover support - the ability to cache its working memory for application restarting or distribution. And of course long-running processes need to be very particular over issues like memory handling - no memory leaks allowed!
The one, really big, difference between Complex Event Processing and traditional BRMS tools is that the former is loosely associated with EDA and decisions that are based on multiple events, whereas the latter is more associated with conventional request-reply SOA and automating decisions made in managed business processes.