A standard metadata declaration must be made for every entity identified with a DOI name according to the following principles:
•The declaration must contain a minimum set of mandatory metadata called DOI Kernel.
This kernel is designed to be as limited in scope as possible, and it is applicable to any entity identifiable by the DOI System.
•Additional metadata can be declared.
It should be based on an agreed metadata exchange schema if metadata interoperability is required with other Registration Agencies (RA).
•All declared DOI metadata is based on a data dictionary which specifies all data elements and allowed values.
The DOI Kernel as well as the data dictionary are specified through the DOI Kernel Schema. This schema is extensible to whatever level of detail and granularity is required, and is neutral (it is independent of any business and any implementation technology). It allows the RAs to use any metadata scheme, yet still ensures semantic equivalence with DOI names assigned by others:
•Terms are added to the DOI Kernel Schema at the request of any RA.
•The DOI Kernel Schema provides the mappings to support metadata integration and transformations required for data exchange between RAs.
The figure below illustrates the metadata creation flow. The registrant of a referent provides the metadata describing the referent. The RA's metadata service creates the corresponding metadata declaration(s) according to the metadata schemas and assigns them to the respective DOI name.
For more information, see DOI Metadata.