Relation pm#P3P_relation (?,?)
  subtype:  expiry  access  optInstructions  abs-date  max-age  start-time  about  base  include  exclude  hint  hintScope  hintPath  includeCookies  excludeCookies  cookieDomain  cookiePath  cookieValue  cookieName  method  disclosure  entity  disputeResolution  service  verification  remedy  statement  consequence  purpose  recipient  recipient-description  retention  data  category  extOptional  extMandatory  dataElementComponent  extends  relativeTo  imageWidth  imageHeight  imageAltText  image  shortDescription  longDescription
  supertype:  relation_coming_from_an_ontology (*)
     supertype:  relation_for_an_application (*)  relation introduced by an application
        supertype:  relation_playing_a_special_role (*)  this type permits to categorize relations according to their roles ; this is a traditional but quite subjective way of categorizing relations
           >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type