Twenty-Five Years of Preferred Subtheories
Résumé
In the seminal paper [6], Gerd Brewka argued that ranking a set of default rules without prerequisites, and selecting extensions according to a lexicographic refinement of the inclusion ordering proves to be a natural, simple and efficient way of dealing with the multiple extension (or “subtheories”) problem. This natural idea has been reused, discussed, revisited, reinvented, adapted many times in the AI community and beyond. Preferred subtheories do not only have an interest in default reasoning, but also in reasoning about time, reasoning by analogy, reasoning with compactly represented preferences, judgment aggregation, and voting. They have several variants (but arguably not so many). In this short paper I will say as much as I can about preferred subtheories in sixteen pages.