How to generate a WebService proxy? What are SOAP, WSDL, and UDDI?

SOAP is an XML-based messaging protocol designed for exchanging formatted data (messages) over the Internet. Using SOAP you can send request and reply messages. SOAP is simple, easy to use, light weight and completely neutral with respect to operating systems, programming languages, and distributed computing platforms. After SOAP came into existence as a mechanism for exchanging XML messages among enterprises, a function was needed to describe the messages and how they are exchanged.

The Web Services Description Language (WSDL) is a particular form of an XML Schema. Developed by Microsoft and IBM for the purpose of defining the XML message, operation, and protocol mapping of a web service accessed using SOAP or other XML protocol. WSDL defines web services in terms of "endpoints" that operate on XML messages. The WSDL syntax allows both the messages and the operations on the messages to be defined abstractly, so they can be mapped to multiple physical implementations. The current WSDL specification describes how to map messages and operations to SOAP 1.1, HTTP GET/POST and MIME. WSDL creates web service definitions by mapping a group of endpoints into a logical sequence of operations on XML messages. The same XML message can be mapped to multiple operations (or services) and bound to one or more communications protocols using "ports".

The "Universal Description, Discovery, and Integration" (UDDI) defines a data model (in XML). Also SOAP API's for registration and searching business information, web services that a business exposes to the Internet are also covered. UDDI is an independent consortium of vendors founded by Microsoft, IBM and Ariba. This project purpose of developing an Internet standard for web service description registration and discovery.

Microsoft, IBM and Ariba also are hosting the initial deployment of the UDDI service. This is conceptually patterned after DNS (the Internet service that translates URLs into TCP addresses).

UDDI uses a private agreement profile of SOAP (UDDI doesn't use the SOAP serialization format because it's not well suited to passing complete XML documents (it's aimed at RPC style interactions). The main idea is that businesses use SOAP APIs to register themselves with UDDI. Other businesses search the UDDI when they want to discover a trading partner.

The information in UDDI is categorized according to industry type and geographical location, allowing UDDI subscribers to search through lists of potentially matching businesses. Once a specific business is chosen, another call to UDDI is made to obtain the specific contact information for that business. The contact information includes a pointer to the target business's WSDL or other XML schema file describing the web service that the target business publishes.

Written by Sandeep Mogulla, Webmaster at www.startvbdotnet.com

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