The Root Concept

The includes a special referred to as the . It is the "root" of the main hierarchy that contain all the in .

All other are descended from this "root" via at least one series of of the (i.e. all other are regarded as subclasses of this ).

The Code is and is named .

Features of the root Concept

All other are of the root .

Unlike other , the root is not a of any other .

Release information in the root Concept

The root has a current that contains information about the release. The , representing earlier releases, are distributed as . The release information is represented in the text of the as indicated in .

Representation of release information in the root Concept


version: 20020131 [R] (first release)


Stylized form

version: yyyymmdd [ status] ( )




The release date in format.



R (release), D (developmental) or E (evaluation).


An optional free text of the release.

Top-level Concepts

that are directly related to the by a single of the are referred to as "Top Level ". All other are descended from at least one Top Level via at least one series of of the (i.e. all other represent subclasses of the meaning of at least one Top Level ).

Many Top-level are intended to represent things outside of (including processes, events, and material entities) in the real world. These include:

Top Level Concepts

Representation of top-level Concepts

Awareness of the top-level is likely to be particularly important when developing technical implementations.

A top-level can be identified by the fact that it has a single referring to the . However, to minimize processing requirements the top-level have designated that are documented in this guide asImportant Concept Identifiers.

Top Level Metadata Concepts

Metadata codes represent structural information about the terminology itself. The Top Level Metadata represent broad groups of metadata.

Top Level Metadata

General Links

Core metadata concept

Foundation metadata concept