To create a collection of GML features, a property type shall be derived by extension from gml:AbstractFeatureMemberType.
By default, this abstract property type does not imply any ownership of the features in the collection. The owns attribute of gml:OwnershipAttributeGroup may be used on a property element instance to assert ownership of a feature in the collection. A collection shall not own a feature already owned by another object.

<complexType name="AbstractFeatureMemberType" abstract="true">
    <annotation>
        <documentation>To create a collection of GML features, a property type shall be derived by extension from gml:AbstractFeatureMemberType.
By default, this abstract property type does not imply any ownership of the features in the collection. The owns attribute of gml:OwnershipAttributeGroup may be used on a property element instance to assert ownership of a feature in the collection. A collection shall not own a feature already owned by another object.</documentation>
    </annotation>
    <sequence />
    <attributeGroup ref="gml:OwnershipAttributeGroup" />
</complexType>

• AbstractFeatureMemberType
• message:BasicMessageMemberAIXMPropertyType
• message:hasMember
• gml:DynamicFeatureMemberType
• gml:dynamicMembers