Just typed out a little pearl in one of the interviews:
RM: yes, that's the other way I think you'd do it; where you'd have initial conditions and then drop the characters in there, and if you created the characters well then the characters would have natural tendencies to do certain things or in a certain manner. So in that process the plot would be almost self-creating, or created through the various discourses.
Why am I so happy about this? Because this is the link between writing for games and writing for books: the plot becomes secondary and there's no longer one discourse, but several discourses as the game evolves.