Recently a chatbot fooled human judges in thinking it is a 13 year old boy for whom English is the second language. Here is the basic details of the structure of this system: it uses a hierarchy of patterns specified in XML structure for state estimation, and a set of rules that activate based on state, with knowledge that is stored in the database. Watch the original conference Chatbots 3.0 conference held in 2010:
Chatbots 3.0 Vladimir Veselov - Eugene Goostman the Bot
Here is the Time's magazine interview with the bot http://time.com/2847900/eugene-goostman-turing-test/
You can chat with Goostman here.