As Web services continue to gain widespread acceptance, there are several compelling business scenarios that will revolutionize the future of application development.

What is a Web service?

It is important to understand the technology behind Web services. Simply put, a Web service can be thought of as an API, or set of related functions, that can be invoked over the Internet. If you’re already familiar with the Component Object Model (COM) technology of the late 1990’s, you’re probably familiar with Distributed COM (DCOM), which was often described as “COM over a longer wire.” In a typical DCOM scenario, an object was created and a function invoked across a machine boundary within the corporate firewall. A Web service extends this concept by allowing us to make a method call across an even longer wire, i.e., across corporate firewalls, and over the Internet.

Another way to think of a Web service is as a Web Site that contains no user interface. Web services can use the same authentication methods that are familiar to ASP developers. Instead of sending back HTML pages that are displayed by a client browser, Web services return the results of method calls in a common XML format.

In this scenario, you need to provide some core set of functionality for multiple web sites. Consider an online mortgage web application that provides monthly payment and amortization information to users upon entering a loan amount and term. Different banks and mortgage companies might provide this functionality, each having its own identity and custom brand, and each having its own “look and feel.”

Instead of building multiple sites, each having its own graphics and business logic, you could develop a single Web service that encapsulates the core business logic (providing mortgage amortization information). Multiple Web sites can be clients to the Web service. Each site would have its own custom branding and user interface, and simply invoke the Web service remotely to calculate the necessary data.

The Internet was originally developed as a means to exchange documents. A user requests a document by typing a URL in a Web browser, it is served up by a remote Web server, downloaded to the user’s machine, and displayed by the Web browser software. As the World Wide Web gained widespread popularity, more and more client-side technology was developed to build full-blown applications that were executed by the Web browser. If you’ve ever developed and deployed an Internet application, you probably felt the pain of developing applications for many different versions of Web browser software. You’ve also probably wished that you could develop a user interface that was truly as rich and compelling as a Windows application using a piece of generic client software that you really have no control over, namely, the Web browser.

Summary

Web services provide a clean separation between data and user interface. You can now have a rich Windows user interface that is truly a native Windows desktop application, plus the ability to access data remotely over the Internet. You are now no longer constrained by Web browser capabilities when developing applications that rely on the Internet as a communications mechanism.