Global Positioning System Reference
In-Depth Information
Elements of a WS-BPEL Web Service composition
WS-BPEL defi nes
'a model and a grammar for describing the behaviour of a business
process based on interactions between the process and its partners.
The interaction with each partner occurs through Web service
interfaces, and the structure of the relationship at the interface level
is encapsulated in what is called a partnerLink.'
(Alves et al. 2007)
From a general point of view, WS-BPEL can be seen as a scripting
language to create applications by composing existing Web services. Like
other Web services standards, WS-BPEL is expressed by using XML, through
XML Schema metadata, and depends on several W3C specifi cations, the
most important of which is WSDL. In particular, the data model used in
WS-BPEL processes is specifi ed using either XML Schema or the message
element of WSDL documents. There can be two types of WS-BPEL
composition (named WS-BPEL process), namely Abstract (useful, for
example, to describe a process “template”) and Executable (fully specifi ed
and executable).
Figure 4 shows the structure of a typical basic WS-BPEL defi nition. The
<PROCESS> element represents the root element of the defi nition. Each
<process>
<partnerLinks>
...
</partnerLinks>
<variables>
...
</variables>
<faultHandlers>
...
</faultHandlers>
<sequence>
...
</sequence>
</process>
Fig. 4. The defi nition of a typical WS-BPEL Process.
 
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