This schema document provides attribute declarations and attribute group, complex type and simple type definitions which can be used in the construction of user schemas to define the structure of particular linking constructs, e.g. ... ... ... ]]> Intended for use as the type of user-declared elements to make them simple links. Intended for use as the type of user-declared elements to make them extended links. Note that the elements referenced in the content model are all abstract. The intention is that by simply declaring elements with these as their substitutionGroup, all the right things will happen. xml:lang is not required, but provides much of the motivation for title elements in addition to attributes, and so is provided here for convenience. label is not required, but locators have no particular XLink function if they are not labeled. from and to have default behavior when values are missing