I have been involved in several projects where one recurring request was to "use BPEL", or more generically "to implement some level of Business Process Management (BPM)". BPEL means Business Process Execution Language and the OASIS Standard defines it as:
"WS-BPEL provides a language for the specification of Executable and Abstract business processes. By doing so, it extends the Web Services interaction model and enables it to support business transactions. WS-BPEL defines an interoperable integration model that should facilitate the expansion of automated process integration in both the intra-corporate and the business-to-business spaces."
An extended definition of SOA says:
"Service-oriented architectures (SOA) promise to implement composite applications
that offer location transparency and segregation of business logic. Location
transparency allows consumers and providers of services to exchange messages
without reference to one another’s concrete location. Segregation of business logic
isolates the core processes of the application from other service providers and
(from: Implementing Service-Oriented Architectures (SOA) with the Java EE 5 SDK - Sun Microsystems)
So basically BPEL allows to segregate business logic into pieces of reusable sequences of atomic business activities, expressed through an XML syntax. SeeBeyond and Sun JavaCAPS 5.1 supported the BPEL 1.x standard through the eInsight engine, while the new, opensource Sun OpenESB supports BPEL 2.0., but there are of course many other products from different vendors.
However the point is that BPEL is about "segregation of business logic", it is not about "arrow and boxes programming". I underline this because I am seeing many projects where BPEL is very misused and abused: they are kind of replacing Java with BPEL because the latter is more buzzword-oriented and all those arrows and boxes look nicer. But then it happens that resulting BPEL is just polluted by technical activities, while I'm stressing the fact it should contain pure business logic. So my hint is to always put your orthogonal concerns (logging, error handling, auditing, etc...) somewhere else and leave your BPEL as clean as possible. For example, with OpenESB (commercially aka JavaCAPS 6) there is a nice JavaEE-SE which is the JBI Service Engine to execute EJBs (practically, it is a JBI bridge to the below application server). Here is a list of all JBI components you can use, have a look at Aspect SE, Camel SE (Apache Camel Service Engine) and Scripting SE for other very interesting opportunities to avoid messing-up your business logic...