Web Service Description Language (WSDL) represents an IDL describing the contract between the service requestor and the service provider in much the same way that a Java interface represents a contract between client code and an actual Java object. The crucial difference is that WSDL is platform- and language-independent and used primarily (although not exclusively) to describe SOAP services.

The subject of Web 2.0 has become profoundly important over the last year. Web 2.0 describes the next generation of the Web as an application platform where most of a user's software experience resides. The subject is somewhat controversial, but it's becoming ever more apparent as the successor to monolithic system architecture, prepackaged software, and traditional Web applications.

I believe that there is a strong tendency for developers to think of Web services as methods. In reality it is not that simple. A Web service defines an XML conversation between client and server. Yet, when a developer sits down to create Web services he or she usually starts by creating a method.

J2EE application servers enabled mainstream developers to build sophisticated multitiered Web applications that use mature standards and any of several commercial and open source application server platforms. A similar pattern has now emerged with the maturation of standard platforms for enabling service-oriented architecture (SOA) through Web services. These Web services platforms provide the same mainstream developer community with design patterns for implementing composite applications that leverage adapters, integration, transformation, business process management, and Web services. This article examines the key requirements for an effective Web services platform, related standards, and what impact this is having on developers and enterprise IT.