Metadata Key

Construct comprised of one or more Object Type/Object Id(s) in order to uniquely identify an item in a collection of reference metadata.

For instance, for a Code or a Concept the Metadata Key would be their Id, such as the URN. For a specific key or partial key there would be two objects, the Data Structure Definition and the Series Key. This is a conceptual structure as it is probable that the Metadata Key would combine the value of all of the individual Object Ids, as this would be necessary in order to find metadata quickly.

Metadata keys can be grouped into Metadata Key Sets.

SDMX, "SDMX Glossary Version 2.0", August 2018