Standards BPEL and BPMN
Todays most known standards in the space of BPM are BPEL and BPMN. Those two standards have a completely different background. That is a clear indication of the diverse type of problems that is currently associated to BPM.
BPEL is defined with an Enterprise Service Bus (ESB) in mind. It's all based on WSDL, which binds naturally to web services. The result of deploying a BPEL process is that a new service is being published. A BPEL process can hence be seen as a scripting language for services on the bus. A more elaborate conceptual explanation of BPEL can be found in Process Component Models: The Next Generation In Workflow ? So BPEL is an executable process language, which implies that a it is human to computer communication, just like a programming language.
On the other hand, the first target of BPMN is modeling process diagrams by non-technical business analysts. It defines the shapes, types and meaning of the boxes and arrows. This type of modeling should be seen in the context of 'BPM as a discipline' (see below). By definition, non technical business analyst do not think in terms of web services or other technology aspects. BPMN processes are primarily intended for communication between humans.
So far, so good. But now comes the hard and confusing reality: BPEL has been presented as a solution for 'BPM as a discipline' and BPMN 2.0 plans to add concrete executable semantics. These days, most IT people already realized that BPEL is not a convenient solution for 'BPM as a discipline'. On the other hand adding concrete executable semantics to a business analyst modeling notation means that non-technical analysts will be implicitly writing a piece of executable software. Would you put software into production written by a non-technical person ?
Use Case 1 : BPM as a discipline
BPM as a discipline refers to the analysis, documentation and improvement of the procedures that describe how people and systems work together in an organization. Realize that most BPM is done in this way, not even resulting into any form of software or IT support. MS Visio is one the most used tools to document business processes.
Of course, once the business process is documented, it might make sense to develop software support for it. Suppose that a business analyst modeled and documented a 'business trip' process, then one usage might be to find optimizations in that process. And another usage might be the development of software support for business trips.
Please be aware that an automatic translation between pure analysis models and executable process models are not feasible in general. Initially BPM products tried to make this translation automagically transparent. In the context of BPM as a discipline, we believe that a process model from a non technical business analyst can never be translated into an executable process model by just adding technical details to it.
The next attempt was to acknowledge existence of an analysis model and an executable process model and then try to keep them in sync. Especially because of the big differences between BPMN and BPEL this approach got a lot of attention. But then the problem of maintaining the links between analysis and executable process model appears. Who is going to spend the time to link the analysis blocks to the executable blocks and then keep that mapping up to date. This is illustrated in the following picture:
For mainstream software development resulting from 'BPM as a discipline', we believe that the original analysis diagram should serve as input with the rest of the software requirements. Developers should then construct an executable process that looks as close as possible to the original analysis diagram. After that, the analysis diagram is discarded and replaced by the executable process diagram. That way, the developer is in full control of the software technical aspects, while the analyst will still recognize the diagram.
jBPM's jPDL language is designed to facilitate this approach. First of all, it's based on free graph modeling. Secondly, it has so called actions, which can be seen as event listeners. These event listeners are pieces of Java code that are called when process execution produces the event, but they are hidden from the process diagram. This allows the developer to add programming logic without changing the diagram structure. Also super-states are often used in the context of creating better communication between business analyst and developer.