Relation pm#Higgins_object_property (?,?)
  supertype:  pm#Higgins_property
  subtype:  higgins#contextRelationship (higgins#ContextObject,higgins#ContextRelationship)
  subtype:  higgins#contextId__contextid (pm#Higgins_Relationship,higgins#ContextId)
     subtype:  higgins#contextURI (pm#Higgins_Relationship,higgins#ContextId)
  subtype:  higgins#attribute (pm#Higgins_ContextObject_or_DigitalSubject,pm#Higgins_Attribute_or_Value)  Instances of this property are used to point to one or more values (i.e. cases where (i.e. cases where the range is higgins:Value). One instance (at most) may also be used to point to a holder of metadata (an instance of higgins:Attribute) about the entire set of values.
     subtype:  higgins#uniqueIdentifier (higgins#DigitalSubject -> higgins#String)
     subtype:  higgins#relation (pm#Higgins_ContextObject_or_DigitalSubject,higgins#SubjectRelationship)  A directed relation between two Digital Subjects
        subtype:  higgins#correlation (pm#Higgins_ContextObject_or_DigitalSubject,higgins#SubjectRelationship)  A directed relation between two Digital Subjects believed to represent the same underlying Entity
     subtype:  pwa#firstname (pwa#Person,higgins#NormalizedStringSimpleAttribute)
     subtype:  pwa#surname (pwa#Person,higgins#NormalizedStringSimpleAttribute)
     subtype:  pwa#postalAddress (pwa#Person,pwa#PostalAddress)
     subtype:  pwa#streetAddress (pwa#PostalAddress,higgins#String)
     subtype:  pwa#city (pwa#PostalAddress,higgins#String)
     subtype:  pwa#state (pm#Higgins_ContextObject_or_DigitalSubject,higgins#String)
     subtype:  pwa#postalCode (pwa#PostalAddress,higgins#String)
     subtype:  pwa#country (pwa#PostalAddress,higgins#String)
     subtype:  pwf#friend (higgins#DigitalSubject,higgins#SubjectRelationship)
  subtype:  higgins#complexMetadata__complexmetadata (pm#Higgins_DigitalSubject_or_Value,?)  Used as the super-Property of some ObjectProperties of higgins:ValueAndMetadata or higgins:DigitalSubject to indicate that these properties are considered to be metadata about the ValueAndMetadata (or DigitalSubject)
     subtype:  higgins#source (higgins#Value,higgins#SubjectRelationship)
     subtype:  higgins#creator (higgins#Value,higgins#SubjectRelationship)
     subtype:  higgins#timeSpan (pm#Higgins_DigitalSubject_or_Value,higgins#TimeSpan)