The HasInterface ReferenceType is a concrete ReferenceType and can be used directly. It is a subtype of the NonHierarchical ReferenceType.
The semantic of this ReferenceType is to show the availability of the Interface on the SourceNode. The Interface concept is described in 4.9.2.
The SourceNode of this ReferenceType shall be an Object or ObjectType. Interfaces shall not be a SourceNode. The TargetNode shall be of a subtype of the BaseInterfaceType.
One SourceNode can refer to different Interfaces.