The bigger the house, the harder it is to keep in order. General Motors, No. 2 on the Fortune 500, ?#8364;œhas one of the largest system integration

challenges of probably anybody on the planet,?#8364;? according to GM?#8364;™s plainspoken CTO, Tony Scott. The company has more than 80 factories across the globe, each with its own mix of enterprise applications. Connecting just one class of application in each factory ?#8364;” inventory, for example ?#8364;” to GM?#8364;™s global SCM (supply-chain management) system means dealing with dozens of different APIs.

?#8364;œIt?#8364;™s very expensive to maintain all these discrete individual interfaces,?#8364;?Scott says. ?#8364;œWe?#8364;™re wrapping them with Web services so that we can abstract what?#8364;™s going on in the plant ?#8364;” and in essence, end up with a common interface to our factories around the world.?#8364;?Going forward, factories will be able to upgrade their apps while the interface stays consistent. ?#8364;œThat saves you money,?#8364;?he adds.

Nothing pleases an IT exec like quick ROI. But from a loftier, architectural perspective, Scott?#8364;™s Web services pilot program has also helped lay the foundation for GM?#8364;™s budding SOA (service-oriented architecture) so that any Web services-enabled application can consume factory inventory data on demand. That SOA vision ?#8364;” in which applications become services and services are rolled into other applications ?#8364;” is driving home Web services?#8364;™ long-touted benefits of application reusability and low-cost integration.

The new momentum is obvious. In a September survey of IT execs, Forrester Research reported that 85 percent of respondents planned to deploy Web services this year, up from 71 percent a year ago. Vendors ranging from Web services startups Actional and Reactivity to stalwarts IBM and Microsoft report surging interest. IBM is training 35,000 Global Services consultants in Web services development; Microsoft is busy building a towering stack of draft Web services protocols into its forthcoming Longhorn version of Windows.

None of this means that the path from a handful of a Web services to a full-blown SOA will be smooth ?#8364;” nor, for some businesses, advisable. The bugaboos of Web services security, performance, management, and QoS still loom. Yet large enterprise customers such as GM, Sony, American President Lines, and Conway profess a long-term commitment; in fact, it?#8364;™s getting hard to find a big company that doesn?#8364;™t. Most are in the planning or early implementation phase. But much can be learned from their work so far, as well as from vendor efforts to provide Web services tools and platforms.

Laying the foundation

Examining the proprietary SOAs of the past also supplies a lesson or two. Dan Foody, CTO of Actional, a provider of Web services management software, is quick to point out that ?#8364;œfinancial services firms have had SOA for 15 years.?#8364;?But financial services companies were among the few that could afford to build and maintain a proprietary SOA. ?#8364;œWhat Web services do is take the burden off the organization. Now the vendors are providing the tools and providing the infrastructure,?#8364;?Foody says.

Those tools proliferate. Visual Studio .Net ?#8364;” Microsoft?#8364;™s Web services-friendly IDE (integrated development environment) ?#8364;” is in its second version, with a third version, code-named Whidbey, shipping in 2004 with major enhancements, including a graphical tool to help developers design and build SOAs. On the J2EE side, the latest versions of application servers and IDEs from BEA Systems, Borland, IBM, and Oracle enable developers to create and deploy Web services without knowing a lick of the underlying XML vocabulary.

In other words, even Joe Developer can now wrap a COM object or a JavaBean in SOAP and publish it as a Web service. The hard part is envisioning how a given organization?#8364;™s ever-expanding set of Web services will work together in an SOA and devising enterprisewide guidelines for writing the WSDL interfaces that describe what each Web service does. An SOA requires an enterprise to re-examine its business processes and to devise a strategy for expressing them in software.

?#8364;œYou need to think about what you want to make available and start there,?#8364;?says Ted Schadler, director of research at Forrester. ?#8364;œThe way that I hear that expressed from people who have already done it is, ?#8364;˜Start with a schema. Start from the outside in. Start with a definition of the service.?#8364;™ ?#8364;?

At RouteOne, a startup that relies on Web services in handling consumer loan applications for auto dealers, Chief Architect T.N. Subramaniam still wrestles with the XML schema and WSDL interfaces that define Web services capabilities. ?#8364;œAn XML schema is a definition of a document. WSDL is actually the entire transaction between two parties,?#8364;?Subramaniam explains. His system hinges on the exchange of Web services documents, which exposes a WSDL limitation. He has found it quite difficult to shoehorn document schema into WSDL descriptions.