Global Positioning System Reference
In-Depth Information
just in time integration thanks to the intrinsic loosely coupled nature
of services;
reduced complexity through a common interface that hides the
implementation differences behind each Web service.
Although the service oriented paradigm and the SOA concept preceded
the arrival of Web services, these latter have become, over time, the most
common implementation of SOA principles so that some concepts and
technologies behind them have infl uenced and contributed to a number
of new SOA characteristics. However, when embedded into a SOA
environment, a Web service needs a supporting infrastructure to offer
its functionalities, which has to guarantee the following basic activities
(Tsalgatidou and Pilioura 2002):
Web service creation,
Web service description,
Web service publishing to intranet or the Internet repositories for
potential users to locate it,
Web service discovery by potential users,
Web service invocation, binding,
Web service un-publishing in case it is no longer available or
needed.
Finally, as for the protocols that allow for the effective exchange of
information among applications, they can be divided into the following
three categories:
Communication protocol,
Service description, and
Service discovery.
For each of them, XML based standards have been defi ned: the SOAP
protocol for the communication, the Web Services Description Language
(WSDL) for the description, and the Universal Description Discovery and
Integration (UDDI) standard for the discovery.
In the following subsections, the SOAP protocol and the WSDL standard
are recalled. In order to be effective, readers should be confi dent with both
Extensible Markup Language (XML) (Fawcett et al. 2012; Zisman 2000) and
the Hyper Text Transfer Protocol (HTTP) (Fielding et al. 1999).
SOAP
SOAP is
'a lightweight protocol for exchange of information in a
decentralized, distributed environment. It is an XML based protocol
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