---------------------------------------------------------------------- --- Knud van Eeden --- 12 October 2003 - 07:08 am -------------------- Problem: Solving: Method: Heuristic: Working backwards: What is the 'working backward from solution' method? --- Start from the goal, and work backwards to the given. --- Or as a special case, work backwards from the answer. --- Thus systematically checking the 'many to one' causes before that which lead finally to this one issue (e.g. error) at the end. --- cut here: begin --------------------------------------------------->-[cause 1]->-+->-[result]->- | ->-[cause 2]->-+ | ->-[cause 3]->-+ | ... | ->-[cause N]->-+--- cut here: end ---------------------------------------------------- --- For example, ask yourself 'Which previous steps could possibly lead to this one error or warning?' Then systematically check and or eliminate as a possible cause this zero or more possibilities. --- For example, ask yourself 'What do I need to know in order to get the solution of the goal?', in other words which information do you minimally need to know or fullfil to be able to solve the problem. === For example: === 1. First ask yourself 'What is my goal?' I want to climb that mountain. So that is your goal. 2. Then you ask yourself 'What are the means to achieve this goal?' 1. Create a list of the necessary means to achieve the goal So you ask yourself: 'What do I need to to be able to climb that mountain'? Answers are for example: a good physical condition, money, time, training, ... After that you try to solve this subproblems. How to get this money? How to get this time (e.g. vacation), ... So you work backwards from the goal towards the means or input, in order to solve the problem. 3. Then solve or find as much means necessary to solve your goal First start to train, save money, organize the trip, ... Finally start climbing, and possibly reach your goal. --- Beginning at the end. When a particular solution state is clearly defined, a problem can often be more easily solved by starting with the solution and working backwards toward the problem, filling in the necessary steps along the way. --- The classic example is the problem: Divide a triangle into three parts so that the parts can be put together to form a square. That is very hard. But if you start from the solution end, with a square, it is easy to divide it into three parts all of which form a triangle. --- Use this backwards working method e.g. when the goal state is clear but the present state is ambiguous. === E.g. President Kennedy stated that he wanted an American spacecraft to go as first to the moon. Here the goal is clear: 'go to the moon'. The means to achieve this goal where less clear: So ask yourself 'how would it be possible to reach the moon?' So possibly generate some mental visual chain of the path from the moon back to the earth. Identify the parts of this chain and work backwards to the beginning. e.g. How would I get land it on the moon. How would I approach it to the moon. How would I fly it to the moon. How would I start it from the earth. How would I get money for it. and so on. After you have solved all that, then you put the pieces together again, such that you possibly reach your goal. === So use this backwards solution method e.g. for: 1. Working backwards to find facts that support hypothesis 2. Use it for diagnosis (medical e.g. MYCIN or general) 3. Use it for extrapolating from the present to the past 4. Use it to follow the path from consequent to antecedent 5. Use it when goal-driven top-down reasoning is necessary 6. As search method, the depth-first search is most easily facilitated here 7. The consequents determine the search === [Internet: source: http://www.google.com search for 'working forward problem solving': http://www.virtualsalt.com/crebook4.htm] === Book: see also: === Diagram: see also: === File: see also: === File: version: control: see also: === Help: see also: === Image: see also: === Internet: see also: --- Problem: Solving: Link: Overview: Can you give an overview of links? http://goo.gl/OXlVX === Podcast: see also: === Record: see also: === Screencast: see also: === Table: see also: === Video: see also: === <version>1.0.0.0.4</version> ----------------------------------------------------------------------
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