More than just a semantic quibble, the question of what truly is Web Services takes many twists and turns. Part of that is because there is no single standards body, so multiple overlapping standards can and do arise (for example, WSDL and UDDI definitely overlap in certain areas). Adding to the confusion is the desire to be buzzword compliant with the latest technology, or to co-opt the standard into some proprietary implementation by claiming it as "Web Services." So we asked the members of our advisory boards, who are all intimately familiar with Web Services in all their flavors, colors, and spins, to answer the question: "What is Web Services?"

We'd like to hear from you as well. Let us know what you think.

From Derek Ferguson, the editor-in-chief of .NET Developer's Journal and chief technology evangelist at Expand Beyond:

At the risk of turning it into a purely semantic debate, I think that there are "web services", and then there are Web Services. Sun, for example, claims to have been doing "web services" for years. However, the standards that support true Web Services have only been in existence for a couple of years at the absolute most. So, clearly - if they mean anything at all - they can't be talking about Web Services that were built using such technologies as SOAP and UDDI.

True Web Services, to me, are just software components that expose their functionality for consumption via XML rather than via a human-centric visual user interface. The value of Web Services is that they adhere to standards - XML and open Internet protocols - that can and have been implemented on virtually every kind of computing machinery devised. Therefore, for the first time, you can have vastly different kinds of software on vastly different kinds of platforms all easily "talking to each other."

To the extent that one deviates from these standards, one eats away at the very value proposition of Web Services - so the XML and exclusive usage of open Internet protocols are really central to my definition of Web Services.

Andy Astor, vice president of enterprise Web services for webMethods, adds to Derek Ferguson's comments : Indeed. The cover story of the premier issue of our own magazine (WSJ) was on Dun & Bradstreet's Web services, which were (and remain) completely SOAP/WSDL/UDDI-free. It's totally appropriate to recognize that there's a valid definition that is conceptual in nature, and that several companies like Sun and webMethods have been doing them for years. Having said that, the conceptual definition just doesn't fly today, precisely because of Derek's main point [see paragraph 2] ...standards mean everyone does it the same way, which enables true interoperability.

Simeon Simeonov is a Boston-based principal at Polaris Venture Partners, with a focus on opportunities in information technology

Tough question. Analysts would define Web Services in different ways. The way I think of it, I see a difference between how Web Services are implemented now and in the future. Right now, a Web Service is any software that can be accessed over SOAP. In the future, a Web Service would be some functionality that is designed for use in a service-oriented architecture. It can be discovered, described and accessed using open, standards-based technology.

Paul Lipton is a director and technology strategist at Computer Associates International, Inc. (CA).

Not to belabor a point, but part of the problem lies in the name "Web Services," which leaves us open to that proposition that strictly speaking every distributed request using Internet protocols, like an HTTP GET request that precipitates an automatic response, is in some sense a Web Service. While true in theory, this is not really true in practice today.

On the other hand, the assumption that Web Services have to include at least these three ingredients (SOAP, UDDI, and WSDL) is also a presumption. There are XML-based alternatives to all of these, but the weight of leading vendors is pushing people down a path. Many will have no choice but to hold their breath, follow the leaders, and hope the water doesn't get too deep! Vendors who are committed to their clients will work hard to minimize the pain for the customers, but there will be stress, of course.

From a spokesperson at Sun Microsystems:
Web services are software components that respond to service requests using a set of open standards. Sun prefers a simple definition of Web services for two reasons: First of all, simplicity is a base characteristic of the fuel necessary to propel Web services into mass adoption - simple verbs connecting virtually infinite nouns. Secondly, the more definitions we tack on to Web services the more we risk limiting their application; Web services is software delivery concept that, in the end, is much bigger and revolutionary than the technical constructs on which current efforts depend.

Web services emerged as a confluence of ideas that emanate from three distinct areas: the Web, XML-based enterprise application integration, and interface-based distributed computing models. Most initial efforts in Web services have involved building standards-based interfaces between internal systems as an alternative to proprietary or "custom-code" integration solutions. This path represents the usage of Web services in a way that is "minimally invasive" in terms of changing the way IT organizations design and build software. As Web services usage expands and matures, the organizations that want to leverage the promises of a services-oriented architecture will need to adopt new approaches, new tools and new development patterns. Here are just a few of the implications that need to be addressed:
1.   Security, management and transactional integrity will need to move from the center of the network out to the edge of the network where most transactions will occur.

2.   Application development will start with process flow definition and interface generation - and code writers will work only where necessary between the connection points.

3.   Current development tools and systems management approaches will need to be fundamentally reengineered to support new realities.

From Bernhard Borges of IBM Business Consulting Services:

Web Services is a concept aligning distributed computing competencies with a specific portfolio of technologies (e.g., XML, TCP/IP), methodlogies (e.g, XML over HTTP - SOAP), and implementations (e.g., specifications -- choreogtraphy) primarily in an open standards manner.