Should facets & metadata be defined on both items and variations?

Any metadata points consistent across all variations should be included on the item level. Data points specific to variations should be included only on the variation level. It is common to have facets or metadata on the variation level that do not exist at the parent level.

For example, a t-shirt made of cotton has multiple sizes (small, medium, and large).

On the item level, a facet would be defined for the material as the value is consistent across all variations:

• item: material: cotton

On each variation, a facet would be defined for the size, as it differs across all variations:

• variation 1: size: small
• variation 2: size: medium
• variation 3: size: large