Is Graffiti art? or is it vandalism?

if the property you wish to paint on does not belong to you and you do not have permission to do such an act then it is considered vandalism no matter how good it is . the question of weather it is art is then besides the point. I've seen some awesome graffitti or art work as some call it but if the painter does not own the canvas I would suggest talking to the owner about using it if you dont want your art work defaced or vandalized