Chapter 5: Collaborate

The evolution of the Internet and its exponential growth in recent years has resulted in a gradual shift from desktop to distributed applications. This shift has led to the development of complex enterprise applications that are managed across different platforms and geographical boundaries.
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Chapter 5: Collaborate Chapter 5Collaborate Knowledge Byte In this section, you will learn about: Web services Securing HTTP endpointsWeb Services The evolution of the Internet and its exponential growth in recent years has resulted in a gradual shift from desktop to distributed applications. This shift has led to the development of complex enterprise applications that are managed across different platforms and geographical boundaries. These applications may consist of components that are developed by using different programming languages and hosted in heterogeneous environments. Therefore, the development of distributed applications involves ensuring that such components are interoperable. For this Microsoft has introduced Web services. Defining a Web Service A Web service exposes a number of methods to provide functionality that can be used by one or more applications, regardless of the programming languages, operating systems, and hardware platforms used to develop them. For example, you can create a Web service by using the .NET platform, which extracts the logon information from the server and returns the result to the client application. This Web service can be used on any operating system and any hardware platform. The methods that provide such functionality are called Web methods. The functionality exposed by a Web service can be accessed by applications by using Internet standards, such as Simple Object Access Protocol (SOAP). SOAP is a protocol that uses Extensible Markup Language (XML) to describe data and HyperText Transfer Protocol (HTTP) for transmitting application data. An application that uses a Web service is called a Web service client. A Web service is similar to a component that provides a specific functionality. However, components use object model-specific protocols, such as Internet Inter-ORB Protocol (IIOP) and Remote Method Invocation (RMI), for communicating with client applications. This communication approach is constrained by dependencies on vendor implementations, hardware platforms, programming languages, and data-encoding schemes. In simple words, the communication approach requires a similar infrastructure at both client and server sides. This approach is acceptable when the use of components is confined to controlled environments. The use of components is not practical on the Internet because the Internet is a huge network of networks, which can be accessed by a Querying, Managing, and Administering Databases Using SQL Server 2005 5.3NIIT wide variety of clients. You cannot expect all clients to use the same infrastructure as that of the component server. In contrast to components, Web services use Internet standards, such as HTTP and XML, to communicate with client applications. This communication approach makes Web services independent of any language or platform. Any computer that has access to the Internet can easily access a Web service. This also enables a number of applications residing on a variety of software and hardware platforms to exchange data. For example, a news network such as CNN can create a Web service, which exposes a method that accepts the news category as a parameter and returns the news items belonging to the specified category. To use this Web service in an application or a website, you can design a form to accept the news category from a user. This form can invoke the method exposed by the Web service and display the news items returned by the method. The architecture of Web services takes the best features of components and combines them with the Web. Depending on the requirements of a business, different types of Web services can be created and used in an application. For example, you can create simple Web services that provide a fundamental functionality, which can be used in multiple applications. You can also create Web services to integrate the existing applications that might have been created by using different software and hardware platforms. Web services can also prove to be useful in business-to-business transactions. Business partners may have applications running on different platforms. These applications can exchange data by using Web services. Enabling Technologies Used in Web Services A Web service can be created by using any programming language in the .NET suite, such as Visual Basic .NET, Visual C# .NET, and Visual C++ .NET. However, certain requirements need to be fulfilled to enable applications to access the functionality provided by Web services. These requirements are: A common data representation format to ensure the interoperability of the data exchanged by the client application and the Web service. A standard method for sending messages from the client application to the Web service and vice versa. A standard format for describing the Web service. A mechanism to allow client applications to discover the Web services and their locations. To cater to these requirements, various standards such as XML, SOAP, and Web Services Description Language (WSDL) are used to develop and access Web services. In addition, the Universal Description Discovery and Integration (UDDI) initiative is used to allow client applications to discover the Web services provided by various Web service providers. NIIT5.4 Querying, Managing, and Administering Databases Using SQL Server 2005 XML A client application passes arguments to a method exposed by a Web service. The method performs some action on the argume ...