Relation pm#relation_to_a_domain__sub-domain_or_object-subdomain (?,pm#domain)
  closed_exclusion:  pm#relation_to_a_thing_that_is_not_a_domain
  supertype:  pm#domain_related_relation__domain-related-thing
  instance of:  pm#virtual_relation_type
  subtype:  pm#subdomain__true-subdomain (pm#domain,pm#domain)  in WebKB-2, ">part" is an abbreviation of this relation since it is not  
 a part relation nor a specialization relation but a mix of both; 
 for details, see http://www.webkb.org/kb/it/o_domain/d_field_of_study.html
  subtype:  pm#subdomain_of_object (?,pm#domain)