Introduction to Web Services

What is a Web Service?

These definitions of Web services have recently been cited in the literature and are generally accepted:

1. Web services provide programmatic access to business functions using standard Internet protocols. Web services perform functions that can be anything from simple requests to complicated business processes. Once a Web service is deployed, other applications (and other Web services) can discover and invoke the deployed service.

2. Web services combine the best aspects of component-based development and the web. Like components, Web services represent black box functionality that can be reused without worry about how the service is implemented. Like the Web, they are accessed using standard Internet protocols (for example, HTTP) and data formats (for example, XML)

3. Web services are a new generation (and generally acknowledged next wave) of e-business applications. Web services result in self contained, self-describing, modular applications that can be published, located, and invoked across the web.

4. Web Services is an emerging technology driven by the will to securely expose business logic beyond the firewall. Through Web services companies can encapsulate existing business processes, publish them as services, search for and subscribe to other services, and exchange information throughout and beyond the enterprise. Web services will enable application-to-application e-marketplace interaction, removing the inefficiencies of human intervention.

5. Web services are computing services offered through the web that are accessible from any web-service-enabled machine with Internet access. Web services enable interoperability through a set of XML-based open standards. Businesses use the XML-based Web Services Description Language (WSDL) to describe their web services on the Internet and list them in an XML-based registry such as the Universal Description, Discovery, and Integration (UDDI) protocol. UDDI allows you to find publicly available web services as shown in Figure 1. A client sends a service request to the directory, which informs the client about the registered services that meet the criteria of the request. The SOAP protocol is then used to communicate, using HTTP and XML as an exchange mechanism, between the applications running on different platforms.

Web Services Standards

Web services are registered and announced using the following services and protocols. Many of these and other standards are being worked out now by