Currently, and id is used in the XML parent element of a Relation, and a idRef is used in the XML child element of a 
Relation:

Proposal: 
- allow idRef in XML parent element of a Relation
- allow id in XML child element of a Relation

Current (remains allowed):

<nml:Link id="urn:ogf:network:provider.com:2012:PortA">
  <nml:Relation type="isSource">
    <nml:Port idRef="urn:ogf:network:client.net:2012:LinkA"/>
  </nml:Relation>
</nml:Link>

Proposal (currently not allowed, may be allowed with this proposal):

<nml:Link idRef="urn:ogf:network:provider.com:2012:PortA">
  <nml:Relation type="isSource">
    <nml:Port id="urn:ogf:network:client.net:2012:LinkA"/>
  </nml:Relation>
</nml:Link>