Code values in a hierarchy are top-level nodes or child nodes. Each hierarchy must contain at least one code value as the top-level node. Top-level nodes are code values at the highest level in a hierarchy and don't have any code values above them. Child nodes are arranged below other code values and can have other code values below them.

The hierarchy relationships that you can create depend on the hierarchy model. A hierarchy model consists of hierarchical relationships between code lists. You define a code list as the top-level code list and then define levels by adding code lists and relationships between the code lists. Then based on the hierarchy model, you can add code values as nodes in the hierarchy.

For example, your organization needs to track country codes by regions. You might create the following hierarchy model:

The following image shows a sample hierarchy model:

With the hierarchy model defined, you might create the following hierarchy:

The following image shows a sample hierarchy:

The relationship between the code values in a hierarchy are termed as related code values.

For example, in the preceding sample hierarchy, the Regions code list contains two code values, such as North America and South America; and the Enterprise Country Codes code list contains two code values, such as Canada and USA. In the hierarchy model, the hierarchical relationship connects the two code lists, and the code values in the parent and child code lists are related to each other.