Service Oriented Architecture

SERVICE-ORIENTED ARCHITECTURE

(Submitted by: Geetika, 14478)

INTRODUCTION:

An emerging approach that addresses the requirement of distributed computing is Service-Oriented Architecture (SOA) [1]. In other words, SOA is that style of architecture whose aim is to achieve loose coupling [] among all the software agents which are interacting with each other [2]. A service is work done by a service provider to fulfil the request made by the consumer of that service. Both service consumer and service provider are software agents which are working on behalf of their owners. Software resources in an SOA are packaged as “services”. Services are self contained modules which provide standard business functionality and are independent of other services.

When this problem came in the notice of researchers, they introduced the concept of modular programming in which programmers could write subroutines or functions and can reuse them wherever required. But this cutting and pasting of modules into other applications made maintenance very difficult; for if, there comes an error the whole application needed to be tracked down to find that error. After that, deployment became a problem because developers wanted higher level of abstraction. Again, developers wanted a way to reuse and maintain functionality and not just the code. Component-based software was a solution to all this but it did not address all the problems developers were facing. Today, many issues are faced which include distributed software, application integration, varying platforms, varying protocols, various devices, internet etc. Today’s software should be capable enough to solve all the above problems and SOA is a solution to it. Adoption of SOA helps in the integration of applications faultlessly.

ARCHITECTURE OF SOA:

The architecture of SOA is as given in the following figure. It consists of two layers- horizontal and vertical which are further divided into sub layers.

A platform-independent interface entails that a client using any type of Operating System or in any language can consume the service. Dynamic discovery

Governance - IT strategy is governed to each horizontal layer to achieve required operating and capability model.

COMPONENTS OF SOA:

Components of SOA comprises of four things namely, message, service, dynamic discovery and web-services. Each of these plays an important role in SOA [soaexp].

• SERVICES: A service in SOA has three properties:

a. The interface used for the service should be platform-independent.

b. The services can be located and invoked vigorously.

c. The service is responsible for maintaining its own state.

• MESSAGES: Service providers and consumers communicate through messages. Because the platform and language at which services are processed is independent of platform, the messages that are sent and accepted should also be platform independent. The messages are constructed using XML document. XML is responsible for providing functionality, granularity and scalability required by messages.

• DYNAMIC DISCOVERY: Dynamic Discovery acts as an intermediate between service provider and service consumer. Providers register their services with dynamic discovery while consumers query it to find the service appropriate to its request. Most directory services categorize themselves based on some criteria so as to make the search