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8.9.  Backtracking

For some problems we may not know how to proceed. For example, suppose we have two packs of cards, one of which has the aces removed, the other the kings. We wish to identify which is the pack without any aces. To do this we guess at one pack, and turn it up until we find a king (it is the right pack), if we find an ace, then it is the wrong pack, and we must put it back. This is the process of backtracking.

In other words: Backtracking allows visiting previously visited nodes. Backtracking in a linear fashion and also the ability to arbitrarily jump to previous nodes helps people to bail out of difficult situations. The most preferred method is the path-following principle which allows traversing, in reverse order, those nodes that were previously visited since this approach relies on the user's memory of his or her own navigation behavior. The structure-oriented feedback approach allows users to directly jump to a node without backtracking. However, experiments have shown that combining these two methods might lead to confusion.

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Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1998).

Last modified: 27/July/98 (12:14)