Gamasutra article on Bottom-Up and Top-Down approach

An interesting article on the top-down and bottom-up approach. Only drawback is that the article is written from a game designer's perspective.

http://www.gamasutra.com/view/feature/130542/game_design_cognition_the_.php?print=1

Another interesting article about these two approaches. And most importantly, pros and cons.

http://whatgamesare.com/2011/03/visual-vs-action-oriented-design-game-design.html