JAXR is one of the API’s in the Java Web Serviced Developer Pack.

From the Sun web site:

The JavaTM API for XML Registries (JAXR) provides a uniform and standard Java API for accessing different kinds of XML Registries. An XML registry is an enabling infrastructure for building, deploying, and discovering Web services. Currently there are a variety of specifications for XML registries including, pre-eminently, the ebXML Registry and Repository standard, which is being developed by OASIS and U.N./CEFACT and the UDDI specification, which is being developed by a vendor consortium.

JAXR enables Java software programmers to use a single, easy-to-use abstraction API to access a variety of XML registries. Simplicity and ease of use are facilitated within JAXR by a unified JAXR information model, which describes content and metadata within XML registries.

JAXR provides rich metadata capabilities for classification and association, as well as rich query capabilities. As an abstraction-based API, JAXR gives developers the ability to write registry client programs that are portable across different target registries.

The JAXR API may be found here.

JAXR was created based on JSR-093.