Cloudware Technologies - Guide to Cloud Computing for Business and Technology Managers - page 320

information among themselves. It is based on XML and uses
common Internet transport protocols like HTTP to carry its data.
SOAP implements a request/response model for communication
between interacting Web Services and uses HTTP to penetrate
firewalls, which are usually configured to accept HTTP and FTP
service requests.

b. Service description : Web Services can be used effectively when a

Web Service and its client rely on standard ways to specify data
and operations, to represent Web Service contracts, and to under-
stand the capabilities that a Web Service provides. To achieve
this, the functional characteristics of a Web Service are first
described by means of a Web Services Description Language.
WSDL defines the XML grammar for describing services as col-
lections of communicating endpoints capable of exchanging
messages.

c. Service publication : Web Service publication is achieved by UDDI,

which is a public directory that provides publication of online
services and facilitates eventual discovery of Web Services.
Companies can publish WSDL specifications for services they
provide and other enterprises can access those services using
the description in WSDL. In this way, independent applications
can advertise the presence of business processes or tasks that can
be utilized by other remote applications and systems. Links to
WSDL specifications are usually offered in an enterprise's profile
in the UDDI registry.

3. Service composition and collaboration standards. These include the fol-
lowing standards:

a. Service composition : This describes the execution logic of Web

Services-based applications by defining their control flows (such
as conditional, sequential, parallel, and exceptional execution)
and prescribing the rules for consistently managing their unob-
servable business data. In this way, enterprises can describe
complex processes that span multiple organizations—such as
order processing, lead management, and claims handling—
and execute the same business processes in systems from other
vendors. The Business Process Execution Language (BPEL) can
achieve service composition for Web Services.

b. Service collaboration : This describes cross-enterprise collabo-

rations of Web Service participants by defining their com-
mon observable behavior, where synchronized information
exchanges occur through their shared contact points (when com-
monly defined ordering rules are satisfied). Service collaboration
is materialized by the Web Services Choreography Description