A UDDI registry provides an exchange for web services. Its purpose is to facilitate the discovery and consumption of web services among different parties that typically are not directly familiar with each other. Each UDDI registry can have its own terms and conditions. Some may require authentication to access free web services. Others may allow publishers to sell their services to third-party consumers. UDDI registries are not a requirement for you to publish and consume web services, but provide a venue for you to either locate a particular web service that you might need without developing it yourself, or to publish your web service for a target audience.
The following screenshot shows the Web Services Explorer accessing the IBM UDDI Test Registry. This registry is one that requires a user name and password: