Web services have the potential to vastly improve everything from software coding to the user experience. But the fundamentals of Web services--assembling applications over the Web using open interfaces and protocols--create their own challenges. What can companies do to ensure that the Web services they build will operate flawlessly and stand up to the rigors of E-business?

One answer is software that tests application performance and functionality. While many vendors are still only planning to develop Web-services testing tools, companies such as Compuware, Empirix, Mercury Interactive, Parasoft, Rational Software, and Segue Software are already putting down stakes in this new territory. Some industry experts expect testing tools to play a big part in the success of Web-services implementations.

"Quality is more important with Web services than other types of applications, because you have all of this loosely coupled software that comes together to form a system and must work together in a perfect state," says Gartner analyst Theresa Lanowitz. "Testing will become a very tactical part of the software development cycle. All of the players in the testing arena will have to have a Web-services story in order to be taken seriously."

Some early adopters of Web services are finding value in this new breed of testing tools. Financial-services firm ABN Amro Bank N.V. is using Parasoft's SOAPtest, which became widely available in April, to test adapter software it developed called Wolf (Web Objects for Legacy Functions). Wolf, based on the Java language, was created two years ago as a way to tie ABN Amro's Web applications to its legacy systems, and company officials say it has improved customer service. A consumer shopping for a mortgage at the company's Web site, for example, can now get an immediate, guaranteed fee on closing costs. Some mortgage lenders can provide only a lengthy list of estimated fees because of limited links between their sites and other internal data sources.

ABN Amro's developers recently extended the software to include Web-services functionality, so Wolf can link any of the company's applications with any data source on the Web. "It will open up a whole new category of data sources for end-user applications," says John Schmuck, testing quality-assessment manager at ABN Amro. The Dutch company, which has $620 billion in assets, has been working to build its business in the United States. It's still determining how it will use Web services in its businesses, but customer satisfaction is key.

Companies must make the Web-services applications as reliable as possible because they may involve customers and business partners, says Klaus Fellner, a product manager for Segue's SilkPerformer tool for testing applications' ability to handle large numbers of users. Earlier this summer, Segue released SilkPerformer 5.1, which can test Java 2 Enterprise Edition or .Net Web services. The more reliable the Web service, "the more attractive you are to your customers," Fellner says.

Several technologies are integral to Web services, including XML, the universal messaging protocol; Simple Object Access Protocol; the Universal Description, Discovery, and Integration format for application identification; and Web Services Definition Language, a common language for application description. These technologies work together to retrieve and deliver data, and the world's biggest software vendors, including IBM, Microsoft, and Oracle, have agreed to support them in their Web-oriented applications and operating systems.