FYI, you can abbreviate some of that:

  Vixen -> Rudolph;
  Vixen -> Prancer;
  Vixen -> Dasher;

Is equivalent to:

  Vixen -> {Rudolph Prancer Dasher}

You can also do:

  {Comet Dancer} -> Vixen -> {Rudolph Prancer Dasher}

Very nice when dealing with larger graphs.