<xs:complexType name="BoundarySurfacePropertyType">
	<xs:annotation>
		<xs:documentation>Denotes the relation of an tunnel or hollow space to its bounding thematic surfaces (walls, roofs, ..).
			There is no differentiation between interior surfaces bounding hollow spaces and outer ones bounding tunnels (one reason
			is, that ClosureSurface belongs to both types). It has to be made sure by additional integrity constraints that, e.g. a
			tunnel is not related to CeilingSurfaces or a room not to RoofSurfaces. </xs:documentation>
	</xs:annotation>
	<xs:sequence minOccurs="0">
		<xs:element ref="_BoundarySurface"/>
	</xs:sequence>
	<xs:attributeGroup ref="gml:AssociationAttributeGroup"/>
</xs:complexType>