Fragment of a class hierarchy

Cnoun_e-nu:

  <>                            ==   Cnoun
  <surf morphon suffop>         ==   Cnoun_e
  <surf orth suffop>            ==   Cnoun_e .

Cnoun_e-um:

  <>                            ==   Cnoun_um
  <surf morphon suffop>         ==   Cnoun_e
  <surf orth suffop>            ==   Cnoun_e .

Cnoun_er-um:

  <>                            ==   Cnoun_um
  <surf morphon suffop>         ==   Cnoun_er
  <surf orth suffop>            ==   Cnoun_er .

Cnoun_e:

  <>                            ==   Cnoun
  <surf morphon suffop plur>    ==   @ + Datplur:<>
  <surf orth suffop plur>       ==   e Datplur:<> .

Cnoun_er:

  <>                            ==   Cnoun
  <surf morphon suffop plur>    ==   @ r + Datplur:<>
  <surf orth suffop plur>       ==   e r Datplur:<> .

Datplur:

  <>            
  <dat>                         ==   n .

Cnoun_um:

  <>                            ==   Cnoun
  <surf morphon stemop plur>    ==   umlaut "<root surf morphon>" .