This type is extended by component types to allow them to be documented. This type is extended by component types to allow attributes from other namespaces to be added. Any top-level, optional element is allowed to appear more than once - Any extensibility element is allowed in any place. Such extensibility elements must be in the substitution group of globalExt or postTypes Either the element attribute OR the type attribute may appear but not both. Alternatively a qualified extensibility attribute which refers to constructs in some type system other than XML Schema may be used. This abstract type is intended to serve as the base type for extensibility elements. It includes the wsdl:required attribute which it is anticipated will be used by most extension elements