Digital Incunabula

Available

 * Pre-release specification: https://web.archive.org/web/20060911215716/http://chs75.harvard.edu/projects/diginc/techpub/registry (Wayback Machine, 2006)
 * No longer available as of 2013

Author

 * D. Neel Smith

Description
From the specification page (preserved 2006-09-11):

Motivation: Registry Services differ from other automated authority lists providing a recursive, hierarchical classification schemes of any depth, and in requiring that all entries in a registry include an attestation in a standard reference scheme for each entry in the registry.