+ <xs:attribute name="columnWise" type="xs:boolean" use="optional" default="false"><xs:annotation><xs:documentation>Set for trees associated with columns of an alignment, sequence or annotation row</xs:documentation></xs:annotation></xs:attribute>
+ <xs:attribute name="columnReference" type="xs:string" use="optional"><xs:annotation><xs:documentation>Refers to annotation row the tree is provided by</xs:documentation></xs:annotation></xs:attribute>