UDDI (Universal Description, Discovery, and Integration) currently represents the discovery layer within the Web services protocol stack.

UDDI was originally created by Microsoft, IBM, and Ariba, and represents a technical specification for publishing and finding businesses and Web services.

At its core, UDDI consists of two parts.

First, UDDI is a technical specification for building a distributed directory of businesses and Web services. Data is stored within a specific XML format, and the UDDI specification includes API details for searching existing data and publishing new data.

Second, the UDDI Business Registry is a fully operational implementation of the UDDI specification. Launched in May 2001 by Microsoft and IBM, the UDDI registry now enables anyone to search existing UDDI data. It also enables any company to register themselves and their services.

The data captured within UDDI is divided into three main categories:

White Pages: This includes general information about a specific company. For example, business name, business description, and address.

Yellow Pages: This includes general classification data for either the company or the service offered. For example, this data may include industry, product, or geographic codes based on standard taxonomies.