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)