BPEL's goal is
to make it possible to write a business process once in BPEL and then run it on any
BPEL environment.
Throughout this chapter, we will talk much about 'processes', as the core of BPEL.
A BPEL process is just like any other process providing standard facilities such as
storage, scope, and fault endpoints. Commands given in a BPEL process are called
activities and the definition of a BPEL process consists of exactly one activity.
A process usually comprises multiple web services that work sequentially to
define a scope. Often, the output from one web service is fed into another web
service. Now, a web service can wait for its input from another web service like
an Airways Baggage Tracking System that sends a 'Request-for-Information' to all
available partner airlines and waits for the baggage information. It may even wait
for several hours. We need to understand that enterprise processes are long running
and complex. A major benefit of implementing a long-running process as a BPEL
process is that the persistence of the process can be provided by BPEL engine, greatly
simplifying the business logic.
Once we have a process up to a longer running life cycle, a number of inter-related
issues come to the forefront. One is synchronous versus asynchronous messaging.
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