org.openecomp.asdc.nodes.VNF:
  #The VNF node is required to be hosted by a VNF_Container
    derived_from: org.openecomp.asdc.nodes.Root
    properties:
      service_name:
        type: string
    attributes:
      #attribute means the value is fulfilled at run-time. 
      service_id:
      #In this case, we consider the VNF node only has the service_id value when the node is instantiated
        type: string
    requirements:
      #the "host" requirement can establish the relationship with a VNF_Container node
      - host :
          capability: org.openecomp.asdc.capabilities.Container
          node: org.openecomp.asdc.nodes.VNF_Container