From a recent interview that Leslie Lamport gave to Mihai Bidiu:
The idea of doing something before coding is not so radical. Any number of methods, employing varying degrees of formalism, have been advocated. Many of them involve drawing pictures. The implicit message underlying them is that these methods save you from the difficult task of thinking. If you just use the right language or draw the right kind of pictures, everything will become easy. The best of these methods trick you into thinking. They offer some incentive in the way of tools or screen-flash that sugar coats the bitter pill of having to think about what you’re doing. The worst give you a happy sense of accomplishment and leave you with no more understanding of what your program is supposed to do than you started with. The more a method depends on pictures, the more likely it is to fall in the latter class.
I find that the worst methods confuse me so much with irrelevant details that I give up before I get to the happy sense of accomplishment. But then I am probably more easily confused than Leslie Lamport.