The structure of a category that houses attributes and captures attribute values for items.
The schema establishes the principle attributes that define elements of a hierarchical category and capture the values for these attributes. Two schemata may share many attributes and their related metadata if they belong to sibling categories. Every attribute within a schema contains metadata that define the attribute, assign a data type, assign a unit of measure for numerical data types, determine whether the attribute may capture multiple values, etc. Typically, a hierarchy will contain multiple schemata for each terminal category and potentially some schemata for non-terminal categories. The term schema may refer to all of the schemata tied to terminal categories.