PRESENTED By
Maulik M Sorathia
Rushikesh S Chaubal

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1.1 What is a Web service?
Web services are distributed application components that are externally available. You can use them to integrate computer applications that are written in different languages and run on different platforms. Web services are language and platform independent because vendors have agreed on common web service standards. A web service is typically an application programming interface (API) or Web API that is accessed via Hypertext Transfer Protocol (HTTP) and executed on a remote system, hosting the requested service.
The W3C defines a "web service" as "a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically Web Services Description Language WSDL). Other systems interact with the web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards."
Unlike traditional client/server models, such as a Web server/Web page system, Web services do not provide the user with a GUI. Web services instead share business logic, data and processes through a programmatic interface across a network. The applications interface, not the users. Developers can then add the Web service to a GUI (such as a Web page or an executable program) to offer specific functionality to users.
Web services allow different applications from different sources to communicate with each other without time-consuming custom coding, and because all communication is in XML, Web services are not tied to any one operating system or programming language.
1.2 The Role of Web Services on Mobile Platform
Web services are an emerging technology that provides interoperability between applications running in different platforms. The Web services technology provide the best approach to Service Oriented Architecture envision of component collaboration for better business requirements fulfillment in large enterprise systems. The challenges in implementing Web services consuming clients for low-resources mobile devices connected through unreliable wireless connections are delimited. The paper also presents a communication architecture that moves the heavy load of XML-based messaging system from the mobile clients to an external middleware component. The middleware component will act like a gateway that lightly communicates with the device in a client-server manner over a fast binary protocol and at the same time takes the responsibility of solving the request to the Web service. Keywords: Web Services, SOA, Mobile Computing, Mobile Devices.
1.2.1 Introduction
The current trend in the application space is moving towards Service-Oriented Architecture (SOA) paradigm which describes a flexible set of design principles for building interdependent and interoperable application components that act like services by implementing a specific functionality and publishing a communication interface to access it. The paradigm envisions component collaboration for better fulfillment of business requirements in large enterprises systems. Systems built with these principles will be more flexible to changes in business requirements as opposed to traditional monolithic systems that are extremely sensitive to any change in one of its subsystems.
The Web services technology evolved from the most logical approach of applying the SOA vision to the Web space. This technology provides interoperability over the Web between applications running on different platforms, ensuring a standardized protocol for business partners to exchange information. Being built over the eXtensible Mark-up Language (XML) and Hypertext Transfer Protocol (HTTP) standard protocols, Web services can be easily deployed and accessed from anywhere over the Web.
1.2.2 Description of Web services
Web services are software components build upon Web-based technologies including HTTP and XML and allow standard means of interoperability over the Internet or intranets between application running on a large variety of hardware and platforms. Web services act like self-contained components that are published, located and invoked over the Web. The key concept behind Web services is to provide a standard platform and operating system independent mechanism for application communication over the Web.
The Web Service Architecture (WSA) proposed by W3 organization relies on a number of Web standards like XML, Simple Object Access Protocol (SOAP), Web Service Description Language (WSDL) and Universal Description Discovery and Integration (UDDI) that allow services to be described, searched and integrated by any application. Main Web services implementations fall into one of the two categories: SOAP Web services and REpresentational State Transfer (REST) Web services introduced for the first time by. SOAPbased Web services are the preferred way to implement the SOA initiative in today's complex and heterogeneous computing environment. SOAPbased Web services present greater flexibility at lower integration costs over RESTful Web services that instead offer great performance through lighter messaging system.