Proposal: the "providesLink" relation define the relation between a switching service and a cross-connect in that 
switching service. A cross-connect is implemented as a nml:Link.

XML Example:

 <nml:SwitchingService id="urn:ogf:network:example.net:2012:myconnectionservice">
   <nml:Relation type=""http://schemas.ogf.org/nml/2013/10/relation#providesLink">
     <nml:Link id="urn:ogf:network:example.net:2012:mycrossconnect">
   </nml:Link>
 </nml:Relation>

RDF Example:

 @prefix nml:    <http://schemas.ogf.org/nml/2013/10/base#>; .
 @prefix nmlrel: <http://schemas.ogf.org/nml/2013/10/relation#>; .
 urn:ogf:network:example.net:2012:myconnectionservice a nml:SwitchingService .
 urn:ogf:network:example.net:2012:myconnectionservice nmlrel:providesLink urn:ogf:network:example.net:2012:
mycrossconnect .
 urn:ogf:network:example.net:2012:mycrossconnect a nml:Port .