IVOA Recommendation: IVOA Registry Interfaces Version 1.0
  Registries provide a mechanism with which VO applications can discover and select resources--e.g. data and services--that are relevant for a particular scientific problem. This specification defines the interfaces that support interactions between applications and registries as well as between the registries themselves. It is based on a general, distributed model composed of so-called searchable and publishing registries. The specification has two main components: an interface for searching and an interface for harvesting. All interfaces are defined by a standard Web Service Description Language (WSDL) document; however, harvesting is also supported through the existing Open Archives Initiative Protocol for Metadata Harvesting, defined as an HTTP REST interface. Finally, this specification details the metadata used to describe registries themselves as resources using an extension of the VOResource metadata schema. 
Kevin Benson, Ray Plante, Elizabeth Auden, Matthew Graham, Gretchen   Greene, Martin Hill, Tony Linde, Dave Morris, Wil O'Mu...
astro-ph.IM