0
Broadly, a hierarchy is a superior/inferior or parent/child relationship. XML is inherently a hierarchical representation of information, as all information is encased in a single root, and some tags are encased within other tags. Within an XBRL instance document, all data is encased within the xbrl root tag. Where XBRL begins to diverge from most other XML implementations is that certain hierarchical relationships are not in the instance itself (XML complexTypes), although taxonomies that use XBRL's tuples (such as XBRL GL) are highly hierarchical in the traditional XML sense. XBRL's linkbases (e.g., presentation, calculation, definintion) permit a wide variety of hierarchical relationships that are communicated with the discoverable taxonomy set (DTS): the order and indentation of a presentation, the weighted summation of parents to children and other abstract relationships. Because of the use of the linkbases, the hierarchies defined by the original developers of the taxonomies can, where permitted and appropriate, be modified by industries, regions and Filers.
