Relation sumo#part__part_of (sumo#object,sumo#object)  this type should have been name sumo#part_of to respect the common reading conventions of parameters; all other mereological relations are defined in terms of this one; it means that the 1st argument is part of the 2nd; note that, since part is a reflexive_relation, every object is a part of itself
  exclusion:  sumo#contains
  subtype:  sumo#proper_part  sumo#piece  sumo#component  sumo#member
  type:  pm#partial_ordering_relation_type  binary_relation that is reflexive, antisymmetric and transitive
  type:  pm#spatial_relation_type  the class of relations that are spatial in a wide sense, e.g., mereological relations and topological relation
  supertype:  pm#spatial_relation_from_entity_with_spatial_feature (sumo#object,*)
     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#part_of (?,?)  this type SHOULD NOT BE USED IN WEBKB (its inverse may be used); this type is only provided for knowledge sharing purposes
     supertype:  pm#mereological_relation (?,*)
        supertype:  pm#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:  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