Service Composition - Guide to Cloud Computing for Business and Technology Managers - page 220

entities. This common view can be used to determine specific deployment
implementations for each individual entity. Choreography offers a means by
which the rules of participation for collaboration can be clearly defined and
agreed to, jointly. Each entity may then implement its portion of the choreog-
raphy as determined by their common view.
10.5 Business Process Execution Language (BPEL)
The development of the BPEL language was guided by the requirement to
support service composition models that provide flexible integration, recur-
sive composition, separation of composability of concerns, stateful conversa-
tion and life-cycle management, and recoverability properties. BPEL has now
emerged as the standard to define and manage business process activities
and business interaction protocols comprising collaborating Web Services.
This is an XML-based flow language for the formal specification of busi-
ness processes and business interaction protocols. By doing so, it extends
the Web Service interaction model and enables it to support complex busi-
ness processes and transactions. Enterprises can describe complex processes
that include multiple organizations—such as order processing, lead man-
agement, and claims handling—and execute the same business processes in
systems from other vendors.
BPEL as a service composition (orchestration) language provides several
features to facilitate the modeling and execution of business processes based
on Web Services. These features include
1. Modeling business process collaboration (through <partnerLink>s)
2. Modeling the execution control of business processes (through the
use of a self-contained block and transition-structured language
that support the representation of directed graphs)
3. Separation of abstract definition from concrete binding (static and
dynamic selection of partner services via endpoint references)
4. Representation of participants' roles and role relationships (through
< p a r t n e rL i n kTy p e > s)
5. Compensation support (through fault handlers and compensation)
6. Service composability (structured activities can be nested and com-
bined arbitrarily)
7. Context support (through the <scope>mechanism)
8. Spawning off and synchronizing processes (through <pick> and
<receive> activities)
9. Event handling (through the use of event handlers)