The definition for a yawl is pretty clear cut:
A two masted sailboat where the aft mast is shorter than the forward mast and the aft mast is set aft of the rudder post.
So what is this?
This yacht is over a hundred years old and categorized as a yawl even though the mizzen is forward of the rudder post. Why?
Well, first off, this yacht has a transom hung rudder, so the only way to get the mizzen aft of that is to set the mizzen on the end of the bumkin!
The rules are pretty clear cut and yet at the same time, there are always exceptions.