Last time I wrote down what I was thinking about narrative categories and how I'd chosen to divide them into three categories (trunk, branch, ad-hoc), and elaborating on the third variant. The other two follow.

The trunk narrative—singular—is the main, central narrative in the story. In sharp contrast with ad-hoc missions, narrative structure is imperative to the trunk narrative. Here, we really want to tell a tale, and the player—the hero—has to be at the center of it. Looking at Oblivion or Morrowind, what constitutes the trunk narrative is clear: In Oblivion, it's the quest to close the oblivion gates and find the lost heir, for instance. In Final Fantasy VII, the trunk narrative is the long and complex affair involving Sephiroth and Jenova culminating with the Meteor event. At any rate, the trunk narrative is the category that most closely resembles classical storytelling.

To ensure coherence, the trunk narrative will likely have to be generated largely up-front, before the game has started, so as to ensure that all the locations the player will end up visiting exist and can affect the game world from the start. The trunk narrative is of utmost importance, and we can't let other narratives upset it to any significant degree, to avoid making it unfinishable or otherwise wildly distort it.

I'm thinking right now of using the well-known monomyth as described by Campbell as a starting point for thinking about trunk narratives. The monomyth is compelling, heroic, and suitable for such a major, over-arching story arc. In addition, since it's so well-known, we don't run the risk of generating something that ends up quirky or difficult to comprehend; while there certainly is a place for more wild narratives in games, we'll leave that to human writers for the time being.

The final type of narrative is the branch narrative. This roughly equates to what is generally called a “sidequest” in role-playing games; basically, a short, mostly self-contained narrative that doesn't have any major impact on the trunk narrative, but is more complex than an ad-hoc mission and has some kind of narrative structure to it. There is expected to be a number of these available in the game, and as they are substantially more complex than mere ad-hoc missions, the rewards are that much greater.

We have a little more liberty in generating these. They can be a little bit more wild than the main trunk storyline, because they are optional and the player will have several of them to choose from. A sensible approach would be to associate these with particular places or factions in the game; for instance, there might be a fortress somewhere involving a short story arc featuring a warlord's daughter being held ransom, or a wizard's tower seeking to reclaim lost magical artifacts.

These quests represent a unique challenge. Unlike trunk narratives, where we can use classic models for hero-centered stories, we need to keep a certain level of detachment here. It's all right and even desirable for the trunk story to involve the player fulfilling a grand destiny and saving the world, but if such stories are doled out everywhere the player goes, the story will be neither believable nor compelling.

I will think more about this later.