Source : Free On-Line Dictionary of Computing

production system
     
        A production system consists of a collection of productions
        (rules), a {working memory} of {fact}s 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}.