Depending on the granularity and complexity of what the Reference Data represents.

Reference data can be structured in various ways depending on its granularity and complexity.

Simple List:

Reference data can be a simple list when it involves basic, discrete values such as country codes or product categories.

Cross-Reference:

When reference data needs to map values between different systems or standards, it can be structured as cross-references. For example, mapping old product codes to new ones.

Taxonomy:

For more complex hierarchical relationships, reference data can be structured as a taxonomy. This involves categorizing data into parent-child relationships, like an organizational hierarchy or biological classification.