Introduction. Business Process Execution
Language for Web Services (called BPEL4WS or simply BPEL in the
rest of this chapter) provides a means of specifying interactions
between web services for accomplishing a potentially long running
Used terms .
WSDL . Web Services Description Language
as described in the corresponding W3C proposed recommendation. This
is a notation for declaring services and the types of data they
accept and produce. Also the term may be used to refer to the
document containing a WSDL description.
partner . A service or application which
interacts with a BPEL process.
(BPEL) script . A document containing
BPEL compatible XML constructs.
(BPEL process) instance . An instance of
a BPEL process, can be running, suspended, aborted or finished.
activity . An activity is a building
block of a BPEL script. Receiving data, invoking other web
services, programming language like control structures are all
examples of activities.
portType . Container for set of abstract
operations see below.
operation . An abstract black-box that
have an XML input or/and output. Services potentially supports four
types of operations: one-way, request-response, notification and
solicit-response; this depends of input and/or output allowed and
what is their order. The BPEL4WS uses one-way and request-response
operations. Operations are grouped in 'ports' which define what
operations a particular service supports.
message . An abstract XML fragment that
is used for operation input and output. In particular this is used
inside SOAP Envelope and for value of the BPEL variables. Also the
WSDL specification specifies how abstract messages will be used as
concrete messages using the SOAP protocol and which encoding will