Task-based explanations

Explaining a knowledge system's conclusions requires, among other things, showing how it has satisfied the logical requirements of its problem-solving task. In one report it was shown how task-based explanation worked in generic tasks (GT); other GT work showed how more complex tasks could be solved using multiple GT modules. Because each GT in a composite GT knowledge system serves a role defined by the higher-level goals it serves (i.e., a GT module is a method that achieves a particular goal of the higher-level task) it is possible to explain the high-level task in terms of the low-level GT explanations. We have introduced the idea of a logical structure for diagnosis, a task solved by composition of several GTs, and its use in explanation. In this article we describe how these ideas work to generate explanations in a composite GT system.