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 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>