An abstraction of a ring to support surface boundaries of different complexity.The AbstractRing element is the abstract head of the substituition group for all closed boundaries of a surface patch.
<element name="AbstractRing" type="gml:AbstractRingType" abstract="true" substitutionGroup="gml:AbstractObject"><annotation><documentation>An abstraction of a ring to support surface boundaries of different complexity. The AbstractRing element is the abstract head of the substituition group for all closed boundaries of a surface patch.</documentation></annotation></element>