Off the top of my head:
Ok, on one hand is a rigid preplanned plot. We force the players through the plot because that''s all there is. Fetch the 4 widgets. If you don''t fetch the widgets, the game state will never change.

On the other hand we have the totally free-form ''game''. Do what you want, hopefully it will be enjoyable enough for you to keep playing. Ugh.

I think there''s a better trick to this. The computer game world needs to be 1-2 steps ahead of the player in terms of planning (quests, plots, etc), but what the player doesn''t need to know is that the game is *only* 1-2 steps ahead. Make the larger plot structure largely devoid of fixed items (the end points might need to be fixed, but that''s about it).

The game would have to keep track of a lot of data about the current game world (is NPC X alive?). Anything the player does not immediately see can be generated behind the scenes as we need it. For example, we don''t need to determine if Official Y was bribed until we reach a decision that depends on that event in the past, or unless the player sees it.

I''m thinking some sort of chaos theory pattern to spawn future events. Hmm. I need to sit down and play with this idea some more.

I think I''ll amend my earlier post - there is some value to having a larger, if skeletal, plot. If we want the game to have a conclusion, and have the player deal with Mighty Evil then things should tend to drift towards that confrontation.

So the finite state machine needs to be weighted to drift towards a climax.

the nice thing would be if you could organize it so that the climax wasn''t particularly fixed. Example: the first time you play the game, you face Evil Wizard Fred, powered by a magic Foo. The second game, you race to Evil Fred, and disrupt any plans he might have for acquiring the magic Foo. So the plot finds another appropriate villain, Evil Lich Bob, who acquires the magic Foo while the hero is dealing with Evil Fred.

Or somesuch.