<complexType name="PolygonPatchType">
  <annotation>
    <documentation>A PolygonPatch is a surface patch that is defined by a set of boundary curves and an underlying surface to which these curves adhere. The curves are coplanar and the polygon uses planar interpolation in its interior. Implements GM_Polygon of ISO 19107.</documentation>
  </annotation>
  <complexContent>
    <extension base="gml:AbstractSurfacePatchType">
      <sequence>
        <element ref="gml:exterior" minOccurs="0"/>
        <element ref="gml:interior" minOccurs="0" maxOccurs="unbounded"/>
      </sequence>
      <attribute name="interpolation" type="gml:SurfaceInterpolationType" fixed="planar">
        <annotation>
          <documentation>The attribute "interpolation" specifies the interpolation mechanism used for this surface patch. Currently only planar surface patches are defined in GML 3, the attribute is fixed to "planar", i.e. the interpolation method shall return points on a single plane. The boundary of the patch shall be contained within that plane.</documentation>
        </annotation>
      </attribute>
    </extension>
  </complexContent>
</complexType>

<attribute name="interpolation" type="gml:SurfaceInterpolationType" fixed="planar">
  <annotation>
    <documentation>The attribute "interpolation" specifies the interpolation mechanism used for this surface patch. Currently only planar surface patches are defined in GML 3, the attribute is fixed to "planar", i.e. the interpolation method shall return points on a single plane. The boundary of the patch shall be contained within that plane.</documentation>
  </annotation>
</attribute>