A nice description of the design and technical choices involved in developing a centralized directory of collection and service description. My belief is that this type of service will become more important as time goes on. Also interesting in that they use POIs.
The JISC Information Environment Service Registry (IESR) is a machine-to-machine middleware shared service providing a single central catalogue of quality descriptions of collections of resources available to researchers, learners and teachers in the UK, along with details of the services that provide access to those collections. The collections and services are described according to a set of metadata, which is defined by IESR, but is based on open standards wherever possible. The prototype registry is implemented as an XML repository indexed with the Cheshire II information retrieval software, with an associated meta-registry to support browsing and data capture. Several interfaces for server-to-server retrieval of IESR XML descriptions are available, as well as a Web interface. [A Registry of Collections and their Services: from Metadata to Implementation]