I'd like to consider it a series of successive approximations.
   Or a common search pattern: cut in half, then in thirds, and
   thirds and thirds 'til you find what you're looking for. It's
   nice when you can get-it-right-the-first-time but most things
   are only that simple on paper. Then you hit reality. tongue
   emoticon -- There's nothing random about trial and error but
   there is great flexibility in the methodology used.