Schema Central > niem40 > topology.xsd > gml:Face
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gml:Face

gml:Face represents the 2-dimensional topology primitive.
The topological boundary of a face (gml:directedEdge) consists of a sequence of directed edges. If provided, the aggregationType attribute shall have the value "sequence".
The optional coboundary of a face (gml:directedTopoSolid) is a pair of directed solids which are bounded by this face. A positively directed solid corresponds to a solid which lies in the direction of the negatively directed normal to the face in any geometric realisation. 
A face may optionally be realised by a 2-dimensional geometric primitive (gml:surfaceProperty).

Element information

Type: gml:FaceType

Properties: Global, Qualified

Content

Attributes

NameOccTypeDescriptionNotes
gml:id [1..1]xsd:IDThe attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs.from type gml:AbstractGMLType
aggregationType [0..1]gml:AggregationTypefrom group gml:AggregationAttributeGroup
universal [0..1]xsd:booleanIf the topological representation exists an unbounded manifold (e.g. Euclidean plane), a gml:Face must indicate whether it is a universal face or not, to ensure a lossless topology representation as defined by Kuijpers, et. al. (see OGC 05-102 Topology IPR). The optional universal attribute of type boolean is used to indicate this. NOTE The universal face is normally not part of any feature, and is used to represent the unbounded portion of the data set. Its interior boundary (it has no exterior boundary) would normally be considered the exterior boundary of the map represented by the data set. Default value is "false".

Used in

Substitution hierarchy

Sample instance

<gml:Face gml:id="ID">
   <gml:metaDataProperty>
      <gml:GenericMetaData>Any text, intermingled with:
         <!--any element-->
      </gml:GenericMetaData>
   </gml:metaDataProperty>
   <gml:description>string</gml:description>
   <gml:descriptionReference/>
   <gml:identifier codeSpace="http://www.example.com/">string</gml:identifier>
   <gml:name>string</gml:name>
   <gml:isolated>
      <gml:Node gml:id="ID">
         <gml:metaDataProperty>...
         </gml:metaDataProperty>
         <gml:description>string</gml:description>
         <gml:descriptionReference/>
         <gml:identifier codeSpace="http://www.example.com/">string</gml:identifier>
         <gml:name>string</gml:name>
         <gml:container>...
         </gml:container>
         <gml:directedEdge>...
         </gml:directedEdge>
         <gml:pointProperty>...
         </gml:pointProperty>
      </gml:Node>
   </gml:isolated>
   <gml:directedEdge>
      <gml:Edge gml:id="ID">
         <gml:metaDataProperty>...
         </gml:metaDataProperty>
         <gml:description>string</gml:description>
         <gml:descriptionReference/>
         <gml:identifier codeSpace="http://www.example.com/">string</gml:identifier>
         <gml:name>string</gml:name>
         <gml:container>...
         </gml:container>
         <gml:directedNode>...
         </gml:directedNode>
         <gml:directedFace>...
         </gml:directedFace>
         <gml:curveProperty>...
         </gml:curveProperty>
      </gml:Edge>
   </gml:directedEdge>
   <gml:directedTopoSolid>
      <gml:TopoSolid gml:id="ID">
         <gml:metaDataProperty>...
         </gml:metaDataProperty>
         <gml:description>string</gml:description>
         <gml:descriptionReference/>
         <gml:identifier codeSpace="http://www.example.com/">string</gml:identifier>
         <gml:name>string</gml:name>
         <gml:isolated>...
         </gml:isolated>
         <gml:directedFace>...
         </gml:directedFace>
         <gml:solidProperty>...
         </gml:solidProperty>
      </gml:TopoSolid>
   </gml:directedTopoSolid>
   <gml:surfaceProperty>
      <gml:Polygon gml:id="ID">
         <gml:metaDataProperty>...
         </gml:metaDataProperty>
         <gml:description>string</gml:description>
         <gml:descriptionReference/>
         <gml:identifier codeSpace="http://www.example.com/">string</gml:identifier>
         <gml:name>string</gml:name>
         <gml:exterior>...
         </gml:exterior>
         <gml:interior>...
         </gml:interior>
      </gml:Polygon>
   </gml:surfaceProperty>
</gml:Face>