A number of blog posts have mentioned NUDS-XML, our approach to interpreting the Numismatic Database Standard fields listed by Sebastian Heath on nomisma.org as an XML data model. NUDS-XML (which could be called "Numismatic Description Standard" since it is not technically a database schema) is an ontology applied to numismatic metadata, influenced by existing metadata standards like EAD, METS, and VRA Core, but also largely reliant on linked open data philosophies. Many numismatic concepts can be linked to resources on nomisma.org through W3C xlink attributes.
While NUDS is still a draft and has not been codified in the form of XSD or Relax NG schemas, it is stable enough for development. Numishare is designed to create, edit, and publish NUDS records for physical coins and conceptual coin-type objects.
Draft documentation for NUDS is now available through the ANS's wiki.