The model feature that is toleranced by the geometric_tolerance is specified by the toleranced_shape_aspect attribute. The toleranced feature is either a shape_aspect, the whole product_definition_shape, a dimensional_size or a dimensional_location. The subtype geometric_tolerance_with_datum_reference is used when there is a requirement to reference either a datum_system or a set of datum_references. The subtype geometric_tolerance_with_defined_unit is used when there is a requirement to specify values with the geometric_tolerance. The subtype_geometric_tolerance_with_modifiers is used when there is a requirement to specify specification operators for the geometric_tolerance. The subtype unequally_disposed_geometric_tolerance is used when there is a requirement to specify an offset tolerance zone. For purposes of reporting by a quality organization, the geometric_tolerance is uniquely identified within the context of a product_definition in the second edition of ISO 10303-47. The attribute description is reserved for local notes associated with a tolerance frame where the information in the note does not duplicate an explicitly modeled construct. A geometric_tolerance and shape_aspects it relates to are usually in the same context (e.g., product_definition). Several geometric_tolerance instances may be arranged in an ordered structure by application of geometric_tolerance_relationship in order to support e.g., stacked tolerance frames. Further specialization of the geometric tolerance is provided by an extensible ENUMERATION geometric_tolerance_modifier. The specializations include: