The gml:directedFace property element describes the boundary of topology solids, in the coBoundary of topology edges and is used in the support of surface features via the gml:TopoSurface expression, see below. The orientation attribute of type gml:SignType expresses the sense in which the included face is used i.e. inward or outward with respect to the surface normal in any geometric realisation.
<element name="directedFace" type="gml:DirectedFacePropertyType"><annotation><documentation>The gml:directedFace property element describes the boundary of topology solids, in the coBoundary of topology edges and is used in the support of surface features via the gml:TopoSurface expression, see below. The orientation attribute of type gml:SignType expresses the sense in which the included face is used i.e. inward or outward with respect to the surface normal in any geometric realisation.</documentation></annotation></element>