See http://www.w3.org/XML/1998/namespace.html and http://www.w3.org/TR/REC-xml for information about this namespace. 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. import namespace="http://www.w3.org/XML/1998/namespace" schemaLocation="http://www.w3.org/2001/xml.xsd" Subsequently, qualified reference to any of the attributes or the group defined below will have the desired effect. In due course, we should install the relevant ISO 2- and 3-letter codes as the enumerated possible values... See http://www.w3.org/TR/xmlbase/ for information about this attribute.