HTML clipboard DISCO: Developers will need a way to discover Web services. Discovery of Web Services (DISCO) provides a way to discover and retrieve WSDL descriptions of services on remote machines. Using the discovery document format (which is also an XML grammar), one can send a discovery document to a remote server and, if any SOAP-enabled services (i.e., Web services) exist, receive back a WSDL description of the services provided. In many cases, developers will not know the URLs of the services. Universal Description, Discovery, and Integration (UDDI) specifies a mechanism whereby Web service providers advertise the existence of their Web services and Web service consumers locate Web services of interest. UDDI is a specification for distributed Webbased information registries of Web services. UDDI is also a publicly accessible set of implementations of the specification that allows businesses to register information about the Web services they offer so that other businesses can find them. UDDI registries are used to promote and discover distributed Web services. The Web Services Discovery Tool (Disco.exe) helps you discover the URLs of Web services located on a Web server. You can also save documents related to each Web service locally. Listing 23.28 shows a sample DISCO document from W3C.

Listing 23.28: A DISCO Document

<disco:discovery>
<disco:discoveryRef ref='folder/discovery'/>
<-- elements from other namespaces -->
</disco:discovery>
<disco:discovery>
<scl:contractRef ref='my1.sdl'>
<scl:contractRef ref='my2.sdl' docRef='my.htm'>
</disco:discovery>
<disco:discovery>
<schema:schemaRef ref='my1.xsd' targetNamespace='http://my.org/my1.xsd'/>
<schema:schemaRef ref='my2.xsd'/>
</disco:discovery>