Bot Techniques: The Wandering Monster Table

In preparation for the talk I'm giving Friday at Allison's unofficial Bot Summit, I'm writing little essays explaining some of the techniques I've used in bots. Today: the Wandering Monster Table!

In D&D, the Wandering Monster Table is a big situation-specific table that makes it possible for you, the Dungeon Master, to derail your carefully planned campaign on a random mishap. You roll the dice and a monster just kind of shows up and has to be dealt with. There are different tables for different scenarios and different biomes, but they're generally based on this probability distribution (from AD&D 1st Edition):


65% of the time you will get a Common monster, like a really big rat.
20% of the time you will get an Uncommon monster, like a hobgoblin.
11% of the time you will get a Rare monster, like a neo-otyugh.
4% of the time you will get a Very Rare monster, like Ygorl, Lord of Entropy.

Note that this doesn't mean you're going to run into Ygorl (Lord of Entropy) once every twenty-five adventures. There are a ton of Very Rare monsters, and Ygorl is just one chaos lord. He can't be everywhere. What this means is that most of the time the PCs are going to experience normal, boring wandering monsters. The values of die rolls fall under a normal distribution, and 68% (~65%) of die rolls will fall between within two standard deviations of the mean. Those are your common monsters.

Go out three standard deviations (95%) and things might get a little hairy for the PCs. Go out four standard deviations (99.7%) and you're looking at something really weird that even the Dungeon Master didn't really plan for. But what, exactly? That depends on the situation, and it may require another dice roll.

The WMT is a really good abstraction for creating variety. I use it in my bots all the time. Here's a sample of the WMT for Serial Entrepreneur:

common = ["%(product)s",
"%(product)s!",
"%(product)s...\n%(variant)s...",
"%(product)s? %(variant)s?",
...
]

uncommon = [
"%(product)s... %(variant)s...? Just throwing some ideas around.",
"%(product)s... or maybe %(variant)s...",
"%(product)s or %(variant)s?",
"Eureka! %(product)s!",
...
]

rare = [
"I don't think I'll ever be happy with my %(product)s...",
"Got a meeting with some VCs to pitch my %(product)s!",
"I'm afraid that my new %(product)s is cannibalizing sales of my %(variant)s.",
"The %(product)s flopped in my %(state)s test market... back to the draw
ing board.",
...
]

very_rare = [
"Am I to be remembered as the inventor of the %(product)s?",
"Sometimes I think about Edison's famous %(product)s and I wonder... can my %(product2)s compare?",
"I haven't sold a single %(product)s...",
"I hear %(billionaire)s is working on %(a_product)s...",
...
]

This creates a personality that most of the time just mutters project ideas to itself, but sometimes (uncommonly) gets a little more verbose, or (rarely) talks about where it is in the product development process, or (very rarely) compares itself to other inventors. The 'common' bucket contains nine entries which are slight variants; the 'rare' bucket contains 32 entries which are worded very differently.

The WMT works the same way in Smooth Unicode and Euphemism Bot. All these bots have their standbys: common constructs they return to over and over. Then they have three more tiers of constructs where the result is aesthetically riskier, or the joke is less likely to land, or a little of that construct goes a long way.

I also use the WMT in A Dull Bot to a more subtle purpose. Each tweet contains a random number of typos, and each typo is chosen from a WMT. One of the common typos is to transpose two letters. A very rare typo is to uppercase one word while leaving the rest of the sentence alone.

The WMT fixes one of the common aesthetic problems with bots, where every output is randomly generated but it gets dull quickly because the presentation is always the same. Since you can always dump more stuff into a WMT, it's an easy way to keep your bot's output fresh. In particular, whenever I get an idea like emoji mosaics, I can add it to Smooth Unicode's WMT instead of creating a whole new bot.

There's a Python implementation of a Wandering Monster Table in olipy.