<xs:documentation>This schema defines attributes and an attribute group
suitable for use by
schemas wishing to allow xml:base, xml:lang or xml:space attributes
on elements they define.
To enable this, such a schema must import this schema
for the XML namespace, e.g. as follows:
<schema . . .>
. . .
<import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/03/xml.xsd"/>
Subsequently, qualified reference to any of the attributes
or the group defined below will have the desired effect, e.g.
<type . . .>
. . .
<attributeGroup ref="xml:specialAttrs"/>
will define a type which will schema-validate an instance
element with any of those attributes</xs:documentation>