gml:Shell 

A shell is used to represent a single connected component of a solid boundary as specified in ISO 19107:2003, 6.3.8.
Every gml:surfaceMember references or contains one surface, i.e. any element which is substitutable for gml:AbstractSurface. In the context of a shell, the surfaces describe the boundary of the solid. 
If provided, the aggregationType attribute shall have the value "set".

Element Information

Model

gml:surfaceMember+
Children: gml:surfaceMember

Attributes

QName Type Fixed Default Use Inheritable Annotation
aggregationType gml:AggregationType optional

Used By

Complex Type gml:ShellPropertyType

Source 

<element name="Shell" type="gml:ShellType" substitutionGroup="gml:AbstractObject">
  <annotation>
    <documentation>A shell is used to represent a single connected component of a solid boundary as specified in ISO 19107:2003, 6.3.8. Every gml:surfaceMember references or contains one surface, i.e. any element which is substitutable for gml:AbstractSurface. In the context of a shell, the surfaces describe the boundary of the solid. If provided, the aggregationType attribute shall have the value "set".</documentation>
  </annotation>
</element>

Sample