. The topological boundary of a face consists of a set of directed edges. Note that all edges associated with a Face, including dangling and interior edges, appear in the boundary. Dangling and interior edges are each referenced by pairs of directedEdges with opposing orientations. The optional coboundary of a face is a pair of directed solids which are bounded by this face. If present, there is precisely one positively directed and one negatively directed solid in the coboundary of every face. The positively directed solid corresponds to the solid which lies in the direction of the positively directed normal to the face in any geometric realisation. A face may optionally be realised by a 2-dimensional (surface) geometric primitive.
Database handle for the object. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs. An external identifier for the object in the form of a URI may be constructed using standard XML and XPointer methods. This is done by concatenating the URI for the document, a fragment separator, and the value of the id attribute.
Source
<complexType name="FaceType"><annotation><documentation>. The topological boundary of a face consists of a set of directed edges. Note that all edges associated with a Face, including dangling and interior edges, appear in the boundary. Dangling and interior edges are each referenced by pairs of directedEdges with opposing orientations. The optional coboundary of a face is a pair of directed solids which are bounded by this face. If present, there is precisely one positively directed and one negatively directed solid in the coboundary of every face. The positively directed solid corresponds to the solid which lies in the direction of the positively directed normal to the face in any geometric realisation. A face may optionally be realised by a 2-dimensional (surface) geometric primitive.</documentation></annotation><complexContent><extension base="gml:AbstractTopoPrimitiveType"><sequence><element ref="gml:directedEdge" maxOccurs="unbounded"/><element ref="gml:directedTopoSolid" minOccurs="0" maxOccurs="2"/><element ref="gml:surfaceProperty" minOccurs="0"/></sequence></extension></complexContent></complexType>