Relation higgins#subjectId__subjectid (SubjectRelationship,normalizedString)
  supertype:  simpleMetadata  Used as the super-Property of some DatatypeProperties whose domain is higgins#ValeAndMetadata or higgins#DigitalSubject to indicate that these properties are considered to be metadata about the ValueAndMetadata (or DigitalSubject)
  subtype:  subjectCUID (SubjectRelationship,normalizedString)