Relationpm#symmetric_relation__symmetricrelation(?,?)this category only serves structuration purposes: it is instance of pm#symmetric_relation_type which is not instance of pm#class_of_inheritable_relation_typesubtype: pm#equivalence_relation pm#different sumo#independent_probability sumo#overlaps_temporally sumo#connected sumo#meets_spatially sumo#overlaps_spatially sumo#overlaps_partially sumo#connected_engineering_components sumo#sibling sumo#legal_relation sumo#spouse sumo#consistent type: pm#symmetric_relation_typewhen (?REL ?INST1 ?INST2) implies (?REL ?INST2 ?INST1), for all ?INST1 and ?INST2supertype: pm#binary_relation_with_particular_mathematical_property (?,?) supertype: pm#relation_with_particular_mathematical_property (*) supertype: pm#relation_with_particular_property (*)this rather fuzzy type permits to group categorization schemes less common than those covered by the previous sibling categoriessupertype: pm#relation__related_thing__relatedthing___related_with (*)type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type