Sometimes we just don’t know
David Harel · 2003
Abstract Have you ever tried putting together a class schedule, pairing courses, time slots, and classrooms with teachers and instructors who have all kinds of constraints? Ever tackled a really hard jigsaw puzzle, full of look-alike pieces? Ever had to pack lots of bulky items of varying sizes and shapes into given boxes, trying to get them all in? These are difficult tasks, you would have to admit. In carrying them out we seem to make local decisions one at a time, often reaching a dead end. If that happens, we backtrack a little, undo a recent decision and try something else instead. We then make some more progress, then backtrack again, maybe even further back than before, and so on. The entire process can take a long, long time.