Hierarchy and Evolution of Identifier Schemes

Some Schemes or Standards build on previous frameworks. Each Identifier is usually governed and guaranteed by an Authority, and usually that also involves a PID Scheme. Multiple Schemes can be based on the same Standard (for example, there are several Schemes derived from URN, from ISNI, and from Z39.88-2004). Standards, if they are formalised, are usually maintained by a Standards Body.

Some Scheme or Standards build on others, for example PURL is based on Z39.88-2004, which, in turn, is based on URN. We do not model this complexity, but record the most ‘derived’ Schema or Standard. For example, for ORCID, we only record that it is based on URN:ISNI, and not that URN is involved too as the basis for ISNI.

Future releases could include this added graph-like interrelationship between Schema and/ or Standards.

Moreover, some Identifiers have Schema as well as Protocol (Resolver) Standards - e.g the Handle System has a standardised resolver protocol. We do not include this information at present.

Identifiers with Protocol-Based Resolver Standards

Some Identifiers not only have a Scheme but also require a specific protocol for resolution.

Example: The Handle System (which powers DOIs) has a standardized resolver protocol.

Currently, the KB does not model Resolver Standards explicitly, but this could be included in future versions.