Relation pm#member_of (*,collection)  this type SHOULD NOT BE USED IN WEBKB (its inverse may be used); this type is only provided for knowledge sharing purposes
  supertype:  relation_to_collection
  subtype:  member (?,set)  this type SHOULD NOT BE USED IN WEBKB: if the common reading conventions of parameters had been respected, the parameters would be swapped or the type would be named member_of