Going out on a far, thin limb here (maybe ;D ) I am working on a game concept and inside this game would be a chat system between players and between npc’s. When talking with an npc, I owuld like to take a typed sentence and parse it out , use some AI to come up with the npc’s possible answers and respond. I know this sounds like a headache, but it is something I want to attempt. Anyone done this? Have any thoughts, other than dont do it this way 
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Iirc Planeshift MMORPG does its npcs like this. Its open source the last I looked too.
http://www.planeshift.it/