Improving Human Decision Making through Case-Based Decision Aiding

ness of Indexes Although cases are specific, indexes to cases need to be chosen so that the case can be used in as broad a selection of situations as appropriate. Often, this approach means indexes should be more abstract than the details of a particular case. Consider, for example, a case from CHEF (Hammond 1986, 1989). CHEF just created a recipe for beef and broccoli, a stir-fried dish. When it first created the recipe and tried it out, it found that the broccoli got soggy. It fixed the order of the steps in the recipe so that the broccoli remained crisp. This case could be indexed in several ways: (1) dish is prepared by stir frying, dish includes beef, and dish includes broccoli and (2) dish is prepared by stir frying, dish includes meat, and dish includes a crisp vegetable. The first set allows this case to be recalled whenever beef and broccoli are to be stir fried together. This index, however, would not allow recall of this case, for example, when chicken and snow peas are to be stir fried. However, the order of the steps probably has to be the same as for beef and broccoli—snow peas are also a crisp vegetable that should remain crisp. Indexing by the second set of descriptors makes this case more generally applicable. Concreteness of Indexes The danger of abstract indexes is that they can be so abstract that the reasoner would never realize that a new situation had these descriptors except through extensive inference. Thus, although indexes need to be generally applicable, they need to be concrete enough so that they can be recognized with little inference. Consider another example from CHEF to illustrate this point. CHEF just created a new recipe for a strawberry souffle. It created this dish by adapting a recipe for vanilla souffle. When it first made the souffle, it fell. CHEF figured out that the problem was that the liquids and leavening were not balanced: There was too much liquid for the amount of leavening in the recipe. It also figured out that the extra liquid was because of the juice in the strawberries. It solved the problem by increasing the leavening to counter the effect of the liquid in the strawberries. This case could be indexed in several ways: (1) dish is of type souffle, and liquids and leavening are not balanced; (2) dish is of type souffle, and dish includes strawberries; (3) dish is of type souffle, and dish includes fruit; and (4) dish is of type souffle, and dish has a lot of liquid. The last three indexes are clearly better Articles