simpleType stringOrNull

namespace	http://www.opengis.net/gml
type	union of (gml:NullEnumeration, xs:string, xs:anyURI)
annotation	documentation Union of the XML Schema string type and the GML Nulltype.  An element which uses this type may have content which is either a string or a value from Nulltype.  Note that a "string" may contain whitespace.
source	<xs:simpleType name="stringOrNull">   <xs:annotation>     <xs:documentation>Union of the XML Schema string type and the GML Nulltype.  An element which uses this type may have content which is either a string or a value from Nulltype.  Note that a "string" may contain whitespace.  </xs:documentation>   </xs:annotation>   <xs:union memberTypes="gml:NullEnumeration string anyURI"/> </xs:simpleType>

XML Schema documentation generated by XMLSpy Schema Editor http://www.altova.com/xmlspy