gml:OrientableSurface 

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".

Element Information

Model

gml:metaDataProperty* , gml:description{0,1} , gml:descriptionReference{0,1} , gml:identifier{0,1} , gml:name* , gml:baseSurface
Children: gml:baseSurface, gml:description, gml:descriptionReference, gml:identifier, gml:metaDataProperty, gml:name

Attributes

QName Type Fixed Default Use Inheritable Annotation
axisLabels gml:NCNameList optional
gml:id ID required 
The 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.
orientation gml:SignType + optional
srsDimension positiveInteger optional
srsName anyURI optional
uomLabels gml:NCNameList optional

Source 

<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>

Sample