BPEL as a Modeling Tool

BPEL can be used to implement workflow and business processes. In theory, BPEL is not tied up with Web services or SOA since all J2EE BPEL vendors support callouts to EJB , JMS or even POJOs in their BPEL implementations (BPELWS, BPELJ ). BPEL has some interesting capabilities, such as the support for asynchronous and long-running processes, transaction compensation, and integration with UI for human activities. But the main point of BPEL is really its visual nature, the fact that the BPEL flow can be modeled in a visual designer tool. If not for that, it would’ve been more efficient to provide the aforementioned capabilities in the form of yet another Java API . The fact that BPEL is “visual” should make it easier to gather requirements and communicate changes to business stakeholders. Some vendors even go as far as proclaiming that now a business analyst can change and optimize a business process without requiring the involvement of a software developer.

However, for any real-life system some logic would still remain in the Java code. At the very least, the Java code would have some kind of persistence support for data transferred by the BPEL flow. More likely, complex business rules, the ones that would be too unwieldy to implement in BPEL will also be coded in Java. Also, since BPEL does not have the reuse capabilities of an OO language, anything reusable will probably be coded in Java (although, a piece of reusable logic could also be implemented as a reusable BPEL subprocess).

So on one hand, BPEL should be pretty high level and the business process‘ activities (and, therefore services APIs) should be coarse-grained. But this will externalize only the most rudimentary logic of the system. Granted, this high level flow could still be useful if the goal is to integrate different (probably heterogeneous) systems, but if we want to use BPEL for its process modeling capabilities, this may prove insufficient. Devil is always in details and so most likely in real life business process changes or optimization will require changes to these complex business rules implemented in Java. In other words, no matter how we try, business people still need to work together with the developers, make sure that the use case are right, changes are thoroughly tested and so on.

On the other hand, implementing very complex detailed business processes in BPEL is probably difficult at best. Visual modeling approach has its natural limits and so at some point it will become much easier to fire up a Java IDE . I guess it is also possible to hand-edit BPEL XML code, although this probably won‘t be pretty either, using XML as a procedural programming language has its limits too.

So what is the right usage of BPEL ? Is just a Web services orchestration language or a general purpose business modeling environment?