ALICE, Artificial Linguistic Internet Computer Entity, is a chat bot created by Richard S. Wallace and probably the most widely known bot of all. ALICE is based on AIML, or Artificial Intelligence Markup Language, an XML specification for programming chat bots. AIML is easy to learn, espcecially if you are already familiar with writing HTML. Standardized AIML sets are available for free, as is ALICE, at the official ALICE site. AIML sets are a standardized knowledgebase of words and partial sentences that the bots use to process information and construct a reply during conversation.
While bots like Leo can learn from directly from the conversations you have, ALICE uses a method of learning called "supervised training". You, the botmaster, are responsible for reading the transcripts, analyzing the responses, and creating new replies for the patterns detected to add more realism and improve the flow of conversation. This is a Case-Based Reasoning system and is similar to the method used to train Siseneg.
There are several different versions of ALICE. There are versions for Windows, Linux, Mac, and the Palm OS and versions written in C and JAVA. You are also able to run ALICE on your own computer or on a web server so other people can talk to your bot. There are versions that allow you the full experience of programming a bot and versions for those who would rather just talk to her and leave the programming to somebody else. There is also a ALICE brain plugin for the UltraHAL bot.
There are also websites that host ALICE free of charge where you can program your own bot that you and others can talk to online.