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 Service-  oriented  architecture  (SOA)

The technical architecture used to build web services is formally known as a ‘

 service- 

 oriented  architecture

’. This is an arrangement of software processes or agents which com-

municate with each other to deliver the business requirements.

The main role of a service within SOA is to provide functionality. This is provided by 

three characteristics:

  1 

An interface with the service which is  platform-  independent (not dependent on a particu-

lar type of software or hardware). The interface is accessible through applications devel-

opment approaches such as Microsoft.Net or Java and accessed through protocols such as 

SOAP (Simple Object Access Protocol) which is used for  XML-  formatted messages.

 2 

The service can be dynamically located and invoked. One service can query for the exist-

ence of another service through a service directory – for example an e-commerce service 

could query for the existence of a credit card authorisation service.

  3 

The service is  self-  contained. That is, the service cannot be influenced by other services; 

rather it will return a required result to a request from another service, but will not 

change state. Within web services, messages and data are typically exchanged between 

services using XML.

The examples of web services all imply a user interacting with the web service. But with 

the correct business rules and models to follow, there is no need for human intervention and 

different applications and databases can communicate with each other in real time. A web 

service such as Kelkoo.com exchanges information with all participating merchants through 

XML using an SOA. The concept of the semantic web mentioned above and business appli-

cations of web services such as CRM, SCM and ebXML are also based on an SOA approach.