gml:AbstractMemberType

To create a collection of GML Objects that are not all features, a property type shall be derived by extension from gml:AbstractMemberType.
This abstract property type is intended to be used only in object types where software shall be able to identify that an instance of such an object type is to be interpreted as a collection of objects.
By default, this abstract property type does not imply any ownership of the objects in the collection. The owns attribute of gml:OwnershipAttributeGroup may be used on a property element instance to assert ownership of an object in the collection. A collection shall not own an object already owned by another object.