sverweij/mscgen_js

msc {
  hscale="2";

  a,
  b,
  c;

  a -> b [label="signal left to right"];
  b -> a [label="signal right to left"];
  a -> a [label="signal to self left to right"];
  a <- a [label="signal to self right to left"];
  a -> "*" [label="signal broadcast left to right"];
  "*" <- b [label="signal broadcast right to left"];
  --- [label="both way stuff"];
  a <-> b [label="signal both ways - starting at a"];
  b <-> a [label="signal both ways - starting at b"];
  a <-> a [label="both way signal to self"];
  a <-> "*" [label="signal both ways broadcast left to right"];
  
  # not supported by mscgen:
  # "*" <-> b [label="signal both ways broadcast left to right"];
}