UML with graphviz' dot

oswald.dot

digraph HelloOswald {
  fontname = "Bitstream Vera Sans"
  fontsize = 8

  node [
    fontname = "Bitstream Vera Sans"
    fontsize = 8
    shape = "record"
  ]

  Object [
    label = "{Object|+ name : string\l|}"
  ]

  Animal [
    label = "{Animal||+ say_hi() : void\l}"
  ]

  Plant [
    label = "{Plant||+ say_hello() : void\l}"
  ]

  Octopus [
    label = "{Octopus|+ hands : integer\l|+ sing() : void\l}"
  ]

  Dog [
    label = "{Dog|+ tail : integer\l|+ bark() : void\l}"
  ]

  Penguin [
    label = "{Penguin||+ play() : void\l}"
  ]

  Flower [
    label = "{Flower||\l+ roller_skate() : void\l}"
  ]

  Egg [
    label = "{Egg|+ brother : object\l|\l+ say_yes() : void\l}"
  ]

  Snowman [
    label = "{Snowman||\l+ walk() : void\l}"
  ]

  edge [
    arrowtail = "empty"
    dir       = back
  ]

  Object -> Animal
  Object -> Plant
  Object -> Egg
  Object -> Snowman

  Animal -> Octopus
  Animal -> Dog
  Animal -> Penguin
  Plant  -> Flower
}