Hi Emily,
not sure if this is too specific a question, but I wonder if you can help me out:
Last NaNoGenMo I started out on doing a more sophisticated version of Meehan’s Talespin. I ended up doing lots of planning, but not too much implementation, so I’m going to continue my efforts this year. The biggest part of it all seems to be a world simulator. This would be where all the actions the characters are planning to do get executed. In a way this seems very similar to what is part of every IF/adventure game (locations, objects, etc), and I have programmed some of those in my micro computer days on a ZX Spectrum… But I feel this needs to be more sophisticated (and on a larger scale), and general, as there will be a multitude of possible actions that can modify the world state. And it might also have to be ‘fractal’ (for want of a better word), as there is landscape in the wild, cities (which are in the landscape, but consist of many locations where there would otherwise just be a single location of forest), and rooms in houses in cities, etc.
Are you aware of any systems in existence that I could use for that? I am kind of hoping it would be similar to a physics package for arcade games, a ready-made package that I can slot my content data and planner actions into. Or do I have to write my own?
Any pointers much appreciated!
I’ll try to answer this in its own terms below, but first I feel like those answers should come with some warnings.
This is presumably obvious, but there is no such thing as a generic world simulator. Any simulation is making decisions about what to model and what to ignore, what level of abstraction to use, what kinds of state are interesting to preserve, and so on. It’s misleading to think of “a world simulator” as “like” a physics engine. A physics engine is a type of world simulator, one that focuses on a comparatively well-defined kind of state: position, velocity, acceleration, elasticity, and so on. (I don’t mean it’s easy to write a good one! Just that the domain of simulation is reasonably defined.)
Text adventure world models tend to focus on rooms, furnishings, and items of the proper size to be carried by a human being, but that’s also very much a subset of what you might theoretically want to model. Items that are abstract (“love”, “communism”), intangible (“the smell of grass”, “a traumatic memory”), larger than a room (“Antarctica”), or smaller than a human being could pick up (“ant”, “quark”) are less likely to be simulated — though of course some of us have worked on extending the world model to include support for conversation topics, knowledge, and relationships.
Moreover, the choices you make about what to simulate will very heavily affect what kind of story you get out the other end. Finally, the way in which your simulation is described will affect how easily it can be plugged into a planner system.
I’d also warn against thinking of the content data as a minor aspect of the system. It’s common for research on story generation to focus on the process: is this grammar-based, is it a planner, is it partially ordered or not, are we forward-chaining or backward-chaining (or a little of each), are we planning the events of the story separately from the discourse layer, how are we measuring coherence and novelty (if those are even our concerns at all). Those are all interesting questions to ask, but the features of the content data also make a very significant difference to output quality, and a corpus implicitly encodes a lot of things about the possible story space that may not be inherently required by the generative method.
In every project I’ve worked on where there was a target output quality (as opposed to toy or experimental projects), most of my development time on a first release has gone into working and reworking the content data, rather than refining the process of generation. Once the qualities of a good data set are well understood, it’s possible to make additional data sets that conform to those expectations in significantly less time, and sometimes to support the process with tooling. But I tend to regard experiments in story generation to be fundamentally unfinished unless the experimenter also presents reasonably polished artifacts of their generative process. If they’re just describing a process and leaving high-quality artifact creation as an exercise for the future, then most of the work is (in my experience) still ahead of them.
So. That is the end of my speech. Now that we’re done with warnings:
Continue reading “Mailbag: World Simulation for Story Generation”
Twice this year I’ve spoken about matching story and mechanics — once for the 
Emily Short's Interactive Storytelling 