Dreamweaver Article

Web services use XML to provide a platform and language-agnostic implementation of distributed application services and information. What this means is that applications and people can use the data and services of an application running on a remote computer regardless of differences between the application server technology running on the remote and local machines. While it's perfectly feasible for a person to use a browser to take advantage of a web service running on a remote computer, the real potential of web services lies in its ability to allow applications to work with other applications without the need for any human intervention.

Unlike other technologies, such as Sun's Enterprise JavaBeans, and Microsoft's DCOM, web services are platform and language-independent. They also don't rely on complex language translations like CORBA. Web services are independent because the messages sent between applications are in an XML-based protocol (called the Simple Object Access Protocol or SOAP). This allows applications written on one application server platform, such as ASP.Net, to be used by applications written in other platforms, such as ColdFusion or Java.

XML and SOAP
Although there are other XML-based web service protocols out there, such as XML-RPC, Jabber, and ebXML, SOAP seems to be the most popular one used with web services today. A discussion of the advantages and disadvantages of these competing technologies is beyond the scope of this article, but you can see some comparisons here. SOAP is a protocol that describes how messages are sent to and from web services.

WSDL
A web services descriptor language (WSDL) file is an XML document that describes the arguments accepted by a specific web service as well as the methods and properties returned by that service. The WSDL specification provides the grammar and syntax rules for WSDL files. As the name implies, these files are used to describe the web service to potential consumers of the web service.

UDDI
Universal Discovery, Description and Integration (UDDI) is the means by which potential users of web services can locate and choose the web service that best meets their needs. UDDIs can be thought of as the marketplace for web services. They are the websites where web service creators can offer and market their services and where users can locate the web service that meets their needs. UDDIs provide information on the organizations providing web services, categorized lists of services registered with the UDDI.org website and specific information on each service listed on UDDI.org.

Currently, there are three main public UDDI services on the web, but this number may change in the future. These include xMethods, the IBM UDDI and the Microsoft UDDI. There are numerous private UDDIs that are not publicized on the web as well. Dreamweaver MX gives you the ability to add or remove UDDIs from the Dreamweaver interface at any time. For more information on adding, configuring and removing UDDI in Dreamweaver MX, consult the online help by choosing Help > Using Dreamweaver and then searching on "web services."

Supported Platforms and Proxy Generators
As I mentioned earlier, Dreamweaver MX has the ability to use existing web services on either ColdFusion MX, ASP.Net, or Java using a J2EE application server such as Macromedia JRun 4. These are the platforms that currently provide proxy generators which can be used with Dreamweaver MX. In addition, Dreamweaver allows you to add and configure web service proxy generators on other application server platforms as web services become supported on those platforms.

Next, you'll take a look at how to use web services using ColdFusion MX.