The latter represent nested structures. In its current incarnation, XML Schema intermingles the two, allowing derivation of complex types from simple ones while deriving the simple urType from the complex one. To me, this state of affairs is unsatisfactory. This addition will increase the expressive power of schemata. Under this scheme, simple types serve to validate text and attributes.
Complex types serve to validate elements only.
Thus, the type hierarchies are completely seperated. To preserve regular processing, all text children of an element must share the same simple type, just as like-named elements do. The following examples specify a complex type with integer content and an integer attribute using the current notation and the proposed one. Text may be typed even if element children are present. Exact sequences of text fragments and elements may be specified.