2.Web Services 2.1 What is web services ...

2.Web Services
2.1 What is web services
Computer science is now in an important period of abstraction. A generation
ago, we learned to abstract from hardware – now we are progressing
by learning to abstract from software. This abstraction is achieved through
service-oriented architectures (SOAs), which allow us to reuse and combine
software components via standardized interfaces, arbitrarily combining them
to serve our needs.
Web services and service-oriented architectures are rather new technologies
with the common goal of making software components and business applications
available via standardized interfaces, within or across enterprise boundaries.
These technologies will facilitate simpler development of distributed
applications and the integration of existing software solutions. The two major
application areas of Web service technologies are as follows:
• Enterprise application integration (EAI). The integration of legacy applications
and systems, which have often been used reliably over years,
is becoming a significant, if not the most important, factor in IT. There
is a strong need for the development of flexible EAI solutions instead of
expensive reimplementation.
• E-commerce. The existing Web interfaces which various providers offer
to their customers mark only the beginning of an increasing economic
sector. Online stores and electronic marketplaces – empowered by Web
service technologies – could profit greatly by integrating and combining
their current services into more powerful, value-added services via common
software interfaces.
Following Preist’s definition,Web services are defined as computational
entities accessible over the Internet (using Web service standards
and protocols) via platform- and programming-languageindependent
interfaces. Returning to our previous example, an airline
might provide a software component accessible via Web service standards,
i.e. a Web service to request the booking of a flight; the Web service is an
electronic means to request a service, but not the service itself. We understand
the term “Web service” as a means to request a service over standard
protocols, described using widely accepted standards. Thus, a Web service
is a means to consume an actual service, or to place a contract for an
actual service.
In very simple terms a web service is a piece of software designed to expose a set of
“methods” –i.e. operations- that can be made available (discoverable) for system
developers to design client applications to use (or consume) that service. These client
applications could be PC applications, web applications running on servers, or
applications running on smart devices such as cellular phones and personal digital
assistants (PDAs).The ...