# navigation hierarchy

## navigation hierarchy

A hierarchical view of SNOMED CT concepts that differs from the subtype hierarchy and enables an alternative way to locate and view part or all of the concept of SNOMED CT.

#### Notes

* SNOMED CT enables *navigation hierarchies* to be specified using either:
  * an *ordered association reference set* in which the display order of nodes can be specified; or
  * an *association reference set* which the display order is not specified.
* The links in a *navigation hierarchy* do not contribute in any way to the semantic definitions of the linked concepts.
* A *navigation hierarchy* may include navigation concepts which are created to represent nodes in the hierarchy exist only to organize the hierarchy and cannot be selected for data entry.
* A *navigation hierarchy* may be limited to a subset of concepts relevant to a particular use case.
* Many different *navigation hierarchies* can be created, each specifying a structure that meets the needs of a particular use case.

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