Relation sumo#domain (pm#relation_type,sumo#positive_integer,sumo#set_or_class)  the formula (sumo#domain ?REL ?INT ?CLASS) means that the ?INT'th element of each tuple in the relation ?REL must be an instance of ?CLASS
  type:  pm#ternary_predicate_type__ternarypredicatetype  class of predicates that require exactly three arguments
  supertype:  pm#relation_from_relation_type (pm#relation_type,*)
     supertype:  pm#relation_from_type (pm#type,*)  type of relations from a concept/relation type, i.e. in RDFS terminology, from a class or a property
        supertype:  pm#relation_from_collection (pm#collection,*)
           supertype:  pm#relation_from/to_thing_of_common_kind (*)  this type permits to categorize relations according to their signatures and hence offers (i) a concise way to set essential exclusion relations, and (ii) a systematic and easy-to-follow categorization
              >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
           supertype:  pm#what_relation (*)
              supertype:  pm#wh-/how_relation (*)  this type permits to categorize relations according to the usual who/what/why/where/when/how questions ; this is a traditional but very subjective and ineffective way of categorizing relations 
                 >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type