Acquiring first-order knowledge about air traffic control

This paper presents an application of knowledge intensive generalization to knowledge acquisition, in the domain of air traffic control. We explain why knowledge intensiveness and first-order logic are sometimes necessary, as for instance in the application field studied here. An obvious advantage of first-order logic is its power of expression, while an obvious drawback is long computation time. We also describe some less obvious advantages and drawbacks of first-order logic, especially when the knowledge must be expressed as Horn clauses to retain some computational efficiency. Finally, we emphasize the large translation problem that must be solved in order to allow an efficient interaction with the expert. Two translation phases are necessary. One goes from the expert's language to Horn clauses, the second one goes back from Horn clauses to the expert's language. The first one is necessary to ensure automatic learning, while the second one allows the expert to understand what has been learned. Both phases are far from trivial and ask for choices that must be made carefully in order to avoid losing significant information. One of our unexpected results is that the second translation phase plays the role of a validation step. It thus becomes a very efficient way to acquire knowledge the expert has problems formalizing. Using first-order logic does complicate things, but it provides, as a reward, a powerful way of extracting and validating the acquired knowledge, especially when the field expert is unable to express his knowledge in a simple way.