...from a thread started on story-games.com...
Narrative Structures are like virtual "skeletons" for the forms of stories that manifest them, but further: they are comprised of molecular units of tension and relaxation, normativity and novelty, which can be organized in ad-hoc ways. If enough of them change in significant ways, you get a different Myth involving the same characters and locations. Tragedy instead of Comedy, perhaps. If the arrangement is highly stochastic, you end up with a chain of dramatic moments that become strung together as a Story in hindsight. If your Narrative Structure has an underlying arc to it, you can design your selections/tables/etc to be indicative of their placement within that arc.
But I think we can go beyond that, even, in terms of futuristic design possibilities. I sometimes imagine the "offstage game state" as a set of "Deleuze-Virtual" multiplicities (i.e., states of being which are "real" even if not currently actualized, such as an unspoken vengeance motive or a hot-headed temperament, or the fact that ice IS water, under the correct circumstances). These little dynamic structures may represent NPCs, or diegetic Forces (such as "militarization"), or non-diegetic Forces (such as "dramatic tension"), depending on playstyle and the "grainsize" of your narrative intentions. It should even be possible to build a little molecular diagram of the possible directions an NPC's or Force's "considerations" or "moods" might go, all of which relate to the logic of the myth (or the narrative structure you're emulating). A "Story" (in hindsight) can be seen as a series of these machines - these little random-but-player-affected dynamic structures - whose very existence or state when encountered may depend on the outcomes of previous encounters with other machines, operating on the same or different levels.
My guess is, just like with the periodic table in physics, we'd discover there's a manageable number of these basic dynamic molecules. Probably in the double digits.
It should be said that my goal right now is not to specify any particular approach, playstyle, or level of randomization, but rather to open up the discourse on randomization and different types of "realness" to levels and elements that may not have been previously considered. A feeling of "realness" may mean anything from physical verisimilitude to narrative coherence to mythological meaning to psychological symbolism.