How can I program a simple chat bot AI?

Question

I want to build a bot that asks someone a few simple questions and branches based on the answer. I realize parsing meaning from the human responses will be challenging, but how do you setup the program to deal with the "state" of the conversation?

It will be a one-to-one conversation between a human and the bot.

Answer 1

You probably want to look into Markov Chains as the basics for the bot AI. I wrote something a long time ago (the code to which I'm not proud of at all, and needs some mods to run on Python > 1.5) that may be a useful starting place for you: http://sourceforge.net/projects/benzo/

EDIT: Here's a minimal example in Python of a Markov Chain that accepts input from stdin and outputs text based on the probabilities of words succeeding one another in the input. It's optimized for IRC-style chat logs, but running any decent-sized text through it should demonstrate the concepts:

import random, sys

NONWORD = "\n"
STARTKEY = NONWORD, NONWORD
MAXGEN=1000

class MarkovChainer(object):
    def __init__(self):
        self.state = dict()

    def input(self, input):
        word1, word2 = STARTKEY
        for word3 in input.split():
            self.state.setdefault((word1, word2), list()).append(word3)
            word1, word2 = word2, word3 
        self.state.setdefault((word1, word2), list()).append(NONWORD)

    def output(self):
        output = list()
        word1, word2 = STARTKEY
        for i in range(MAXGEN):
            word3 = random.choice(self.state[(word1,word2)])
            if word3 == NONWORD: break
            output.append(word3)
            word1, word2 = word2, word3
        return " ".join(output)

if __name__ == "__main__":
    c = MarkovChainer()
    c.input(sys.stdin.read())
    print c.output()

It's pretty easy from here to plug in persistence and an IRC library and have the basis of the type of bot you're talking about.