This may be hair-splitting, but when I say dot I mean a mathematical point. Of course it does not matter how we represent a zero-dimensional object in a graphic

This may be hair-splitting, but when I say dot I mean a mathematical point. Of course it does not matter how we represent a zero-dimensional object in a graphical scene (we need some kind of representation, obviously). My point was the emphasis on "XY coordinates". It is just a suggestion to be more precise here.