Relation pm#topic (?,entity)
  supertype:  Description  to specify an account of the content of a resource; in WebKB, pm#topic or pmdescr SHOULD BE USED INSTEAD
  subtype:  annotation (?,description_content/medium/container)
     subtype:  descr (?,description_content/medium/container)  for connecting an object to a formal representation of it, e.g., a representation written with a fcg
     subtype:  Subject (description,entity)  to specify 1 or several topics; in WebKB, pm#descr SHOULD BE USED INSTEAD
     subtype:  origin (?,description_content/medium/container)
     subtype:  use (?,description_content/medium/container)
     subtype:  advantage (?,description_content/medium/container)
     subtype:  disadvantage (?,description_content/medium/container)
     subtype:  definition (?,description_content/medium/container)  see also #definition
        subtype:  definition (description_content/medium/container,description_content/medium/container)  a logical relation should be used instead of this relation
     subtype:  role (?,description_content/medium/container)
     subtype:  requirement (?,description_content/medium/container)
     subtype:  issue (?,description_content/medium/container)
     subtype:  trap (?,description_content/medium/container)