The index-base element can only exist as a child of an indexterm element. This characteristic makes it the appropriate element to specialize to add indexing extensions. For example, the index-see, index-see-also, and index-sort-as elements only make sense as children of indexterm and so are specializations of index-base. Those elements are all part of the indexing domain.

On its own, index-base has no meaning. Processors should ignore this element and its content if encountered in its unspecialized form.

See appendix for information about this element in OASIS document type shells.

- topic/index-base

The index-see-also element is specialized from index-base; see index-see-also for an example of how index-base can be used with specialization.

The following attributes are available on this element: Universal attribute group and keyref.