Relation pm#relation_to_spatial_object (*,spatial_object)  in WebKB, prefer using relations "from" a spatial object
  subtype:  relation_to_another_spatial_object  where_fn
  supertype:  spatial_relation_to_entity_with_spatial_feature (*,object)
     supertype:  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:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type