From: ted.dunning@gmail.com   
      
   On May 1, 6:43 am, sarah  wrote:   
   > hello there   
   > I am a beginner in AI. I don't know what does knowledge extraction   
   > tool means. In addition I don't know the meaning of Individual in AI.   
   > I want to know the meaning of Rule Discovery,too. Can any one explain   
   > these words to me in simple sentences?   
   >   
      
   Ahh my....   
      
   My guess is that nobody will be able to fully explain these terms in   
   simple sentences because AI is still a very formative field even after   
   50 years or more.   
      
   The terms you are asking about come from a subset of AI in general   
   that is concerned with the encoding of apparently intelligent behavior   
   in terms of rules.  These rules generally take the form of "if   
   something then something else".  The something can be any condition   
   that might be observed by the computer, the something else can be an   
   action taken by the computer, or simply a conclusion that could be   
   used later in other rules.   
      
   The simple fact is, these rule systems are hard to build.  That is,   
   they are easy to start, but hard to maintain once they get to a   
   certain size.   There are many reasons for this, but the primary one   
   is that rules based on hard and fast inference are highly susceptible   
   to problems when contradictions are found.  As well, there can be   
   subtle inferences that drive surprising (and often totally wrong)   
   inferences.  It is incredibly hard to build a rule system that is not   
   subject to these problems and which still has interesting and   
   substantial uses.  Ultimately, all previous systems of this sort have   
   been subject to a break-even point were every additional fix to   
   improve behavior in some situation causes as many problems in other   
   situations.  Once this point is reached, it is essentially impossible   
   to improve the system by simply adding or modifying rules.   
      
   The tools that people use to build these systems have as their primary   
   goal to make this break-even point be as high as possible and to   
   develop a set of rules that has useful behavior as quickly as   
   possible.  Somewhat pretentiously, the discipline of building these   
   systems is known as "knowledge engineering" and the process of   
   eliciting rules from previously observed data or from domain experts   
   is called knowledge extraction.  A knowledge extraction tool is   
   something that makes knowledge extraction more feasible.  Rule   
   discovery is usually used to describe the extraction of rule-based   
   knowledge from observed data rather than from experts.   
      
   Keep in mind, though, that knowledge-based tools are simply one kind   
   of AI of many.   
      
   Two good starting points are the wikipedia article on AI and Peter   
   Norvig's book on the subject.   
      
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