Copy from here: The UDDI Technology white Paper [from ZDNet]

Universal Description, Discovery, and integration (Universal Description, Discovery and Integration UDDI) is a specification of information registration for distributed Web services. At the same time, UDDI is also a public specification by which an enterprise can register the Web services it provides in order to be discovered by other enterprises.
Web services will lead to yet another revolution in the Internet, which enables any organization or individual to publish objects with programming interfaces through a Web site, and to fully use this distributed feature. The purpose of UDDI registration is to facilitate the development of such distributed Web services and to help discover them. This white paper illustrates the effectiveness of this combination of registration and the Internet.
The possible readers of this article are all who want to know about UDDI. This article will help them understand what UDDI is, who uses it, and how distributed registration enables your program to discover and interact with Web services provided by other companies.
　
　
Brief Introduction
Overview
The UDDI specification defines a way to publish and discover Web services. The term Web service describes a particular business service that is typically provided by an enterprise through the Internet, and is intended to provide a way for other companies or software to use these services.
WEB services are becoming a key part of E-commerce. For example, a company sends orders directly by calling another company's services over the Internet. For example, a service that calculates the required transport costs according to the size or weight of the package.
At first glance, "discover" Internet service seems very simple, if a known business partner provides a known E-commerce portal, then what need to find? Note, however, that the prerequisite here is that the information is known. When you want to find out which business partners provide which services, the situation immediately becomes complicated. One way is to call each business partner and find the right person to ask. It is not realistic for a company that provides Web services to hire senior technicians to cope with uncertain service queries.
Another way to solve this problem is through the Web Service description language that exists on each enterprise site. In this way, at least those web crawler programs that rely on URLs that have already been registered can find and index them. But this method of locating Web services through "robots.txt" relies entirely on the ability of a crawler program. This kind of distributed positioning is extensible, but it lacks a mechanism to ensure consistency of service description format and can not easily track the changes that occur continuously. UDDI is registered for the enterprise and the Web services they provide, and Web services are described in a common XML format.
　
　
UDDI Business Registration
A central part of UDDI is UDDI Business registration, and the enterprise itself and the services it provides are described by an XML file. Conceptually, the information provided by UDDI Business registration consists of three parts: "White Pages" include the address of the enterprise, the contact method and the recognized identifier; "Yellow Pages" includes standard industry classifications; "Green pages" include technical information about the services provided by the enterprise. The green page also contains an association with the service description and, if necessary, an association with other discovery mechanisms based on files or URLs.