How Does UDDI Work?

As Figure 31.1 shows, the players communicate exclusively using SOAP messages and SOAP responses. In a sense, you can say that the UDDI Inquiry and Publish calls are themselves Web services. Contrary to what you might think, the UDDI API is not a programmatic, language-specific API. That is, each UDDI API as defined in the UDDI specifications is not a programmatic function call. Instead, each API call is actually a distinct SOAP message and response. Therefore, a server that claims to implement the UDDI API must understand each of these SOAP calls, perform the necessary call logic, and then respond appropriately with a SOAP response message.

A UDDI registry can be hosted by one or more UDDI operators , or nodes . A UDDI operator implements the UDDI API and, of course, also implements the necessary back-end logic to persist the registry information and perform lookups on that persistent store. UDDI does not prescribe any particular implementation or persistence mechanism. A UDDI operator has one other critical responsibility: to make sure all information in all UDDI nodes is synchronized. That is, a client should be able to inquire from any UDDI node and receive the same results.