OrientableSurface consists of a surface and an orientation. If the orientationis "+", then the OrientableSurface is identical to the baseSurface. If the orientation is"-", then the OrientableSurface is a reference to a gml:AbstractSurface with an up-normalthat reverses the direction for this OrientableSurface, the sense of "the top of thesurface".
Database handle for the object. It is of XML type ID, so is constrained to beunique in the XML document within which it occurs. An external identifier for the object inthe form of a URI may be constructed using standard XML and XPointer methods. This is doneby concatenating the URI for the document, a fragment separator, and the value of the idattribute.
<element name="OrientableSurface" type="gml:OrientableSurfaceType" substitutionGroup="gml:AbstractSurface"><annotation><documentation>OrientableSurface consists of a surface and an orientation. If the orientation is "+", then the OrientableSurface is identical to the baseSurface. If the orientation is "-", then the OrientableSurface is a reference to a gml:AbstractSurface with an up-normal that reverses the direction for this OrientableSurface, the sense of "the top of the surface".</documentation></annotation></element>