Heuristic Functions

A Heuristic technique helps in solving problems, even though there is no guarantee that it will never lead in the wrong direction. There are heuristics of every general applicability as well as domain specific. The strategies are general purpose heuristics. In order to use them in a specific domain they are coupler with some domain specific heuristics. There are two major ways in which domain - specific, heuristic information can be incorporated into rule-based search procedure.

   - In the rules themselves
   - As a heuristic function that evaluates individual problem states and determines how desired they are.

A heuristic function is a function that maps from problem state description to measures desirability, usually represented as number weights. The value of a heuristic function at a given node in the search process gives a good estimate of that node being on the desired path to solution. Well designed heuristic functions can provides a fairly good estimate of whether a path is good or not. ( " The sum of the distances traveled so far" is a simple heuristic function in the traveling salesman problem) . the purpose of a heuristic function is to guide the search process in the most profitable directions, by suggesting which path to follow first when more than one path is available. However in many problems, the cost of computing the value of a heuristic function would be more than the effort saved in the search process. Hence generally there is a trade-off between the cost of evaluating a heuristic function and the savings in search that the function provides.