[W/K] :: production system

  production system
       
          A production system consists of a collection of productions
          (rules), a working memory of facts and an algorithm
          known as forward chaining for producing new facts from old.
          A rule becomes eligible to "fire" when its conditions match
          some set of elements currently in working memory.  A conflict
          resolution strategy determines which of several eligible
          rules (the conflict set) fires next.  A condition is a list
          of symbols which represent constants, which must be matched
          exactly; variables which bind to the thing they match and "<>
          symbol" which matches a field not equal to symbol.  Examples
          are OPS5, CLIPS, flex.