Software is continuing to evolve, from the traditional locally hosted applications operating in a closed environment to web services. The web services computing model revolutionizes technology by allowing remotely located individuals to harness information assets and invoke services from virtually anywhere. In order to utilize this technology, one needs to know information about the service provider, such as the protocol of communication, network address, encoding schemes, and method details. Web Services Description Language (WSDL) provides this capability by using XML to communicate this information. WSDL is defined as "an XML grammar for describing network services as collections of communication endpoints capable of exchanging messages."

One of my early uses of Web services, back in 1999, predated SOAP and WSDL. It was a script to calculate what I called Web mindshare. It combined Yahoo’s capability of enumerating sites in a category with AltaVista’s capability of counting inbound links to each of those sites. It was a primitive version of what Google, then in beta, went on to prove dramatically: Links measure authority. What interested me even more, though, was how easily that little script was able to compose a novel service — ranking everything in a category — from two existing but unrelated services.

This page provides links to various services in the wild. Note that these are examples, and may or may not be available at any given time.

This month, the W3C officially began the process of exploring standards for the way web services will exchange business rules for workflow -- both within an enterprise and between businesses. But even before the working group holds its first meeting, political and technical rifts among vendors might limit the work's impact.

This appendix describes how to operate the J2ME Wireless Toolkit tools from the command line and details the steps required to build and run an application. It also describes the J2ME Wireless Toolkit’s certificate manager utility, called MEKeyTool (Mobile Equipment KeyTool) and the MIDlet signing utility, called JAD Tool (Java Application Descriptor Tool).

The RPC (Remote Procedure Call) mechanism enables a remote procedure call from a client to be communicated to a remote server. An example use of an RPC mechanism is in a distributed client/server model. A server defines a service as a collection of procedures that are callable by remote clients. A client calls procedures to access service defined by the server.

This example shows how to develop a Document Literal style webservice for Oracle 10iAS using the Top-Down paradigm. Document Literal webservices are services that process xml documents. The Top-Down paradigm implies that you are starting with a WSDL and will write the implementation classes after the WSDL has been processed and the necessary service classes and interfaces are generated. Once the generation process is complete your implementation class can be compiled and included into the webservice archive (EAR file) to be deployed to OC4J. For your convenience this example has an implementation class and corresponding source code.

On 12th August 2003 WS-I (Web Services Interoperability Organization) announced the release of the final specification of Basic Profile 1.0 a set of recommendations on how to use web services specifications to maximize interoperability. For developers, users, and vendors of web services and web services tools this is a big leap forward to achieving interoperability in the emerging and fast changing world of web services. But what else has WS-I been working on?

In my prior articles, I've introduced and discussed various aspects of the JAX Pack, a set of APIs for working with Web services and the underlying supporting protocols. In this article, we'll look at JAX-RPC, a specification for making remote procedure calls via XML and SOAP over HTTP. Specifically we'll look at the client side of JAX-RPC, as it shows the most promise.

Service discovery defines a process for locating service providers and retrieving service description documents and is a key component of the overall Web services model.

A Web Service is a program that can be invoked in a distributed web environment. Web Service technologies like SOAP, WSDL, and UDDI are standards to describe, publish, discover, and use Web Services; they define a development model for integrating applications over the web.

This example shows you how to use JAX-RPC to create a Web service named HelloWorld. A remote client of the HelloWorld service can invoke the sayHello method, which accepts a string parameter and then returns a string.

Overloaded methods may or may not be what you need for the project you are working on. Additionally, there are those who argue that if a function is taking a different set of argument-types, then it should be noted by giving it a different name. But neither of these are the argument for learning how to express overloaded interfaces in WSDL. The reason is simple: languages, commercially in use today, support this feature. In order to correctly describe their interfaces using a description written in WSDL, it must be possible to describe an operation that has different calling syntaxes.

W3C has acknowledged receipt of a 2002-02-04 submission from the Hewlett-Packard Company for a Web Services Conversation Language (WSCL). The published Note "proposes a simple conversation language standard that can be used for various Web-service protocols and frameworks.

In a previous article ("WSDL Tales From the Trenches, Part 1"), I painted a big picture of web services design. As I said, Web Services Description Language (WSDL) only defines the syntax of how a web service may be invoked; it says nothing about its semantics. I will observe this distinction in what I say in this article about WSDL.

This is the interface part of the service definition file.

One of the best aspects of WSDL is that you rarely have to create WSDL files from scratch. A whole host of tools currently exists for transforming existing services into WSDL descriptions.

This is service definition file. Note that there are three complexType XSM definition which will result in three auxiliary classes defined by wsdl2java.

Using WSDL in a UDDI Registry, Version 1.08

One of the advantages of WSDL being written in XML is that the syntax is easily processed by applications while still being human readable. However, if you have ever thought that all these XML tags get in the way and longed for a more traditional syntax (as used in many programming languages), then this one line of text is the solution to your problems.