This document provides a specification for an extension to a metadata registry (MDR), as specified in ISO/IEC 11179-3:2023, in which metadata that describes concept systems can be registered.

The specification in this document, together with the relevant clauses of the specification in ISO/IEC 11179-3, provides the ability to record the following metadata:

• concept systems and associated concepts;
• relations among concepts in a concept system;
• assertions about concepts in a concept system.

The metamodel in this document is intended to support the full description of a concept system, including ontologies.

Where there is a requirement to register an ontology where the details are defined elsewhere, consider using ISO/IEC 19763-3 instead.