DELORES (DEfeasible LOgic REasoning System) is a forward-chaining reasoning engine for defeasible logic, a less-expressive but more efficient non-monotonic logic. In contrast with most other non-monotonic logics, defeasible logic has linear complexity, allowing DELORES to execute large theories very quickly. DELORES's algorithm extends to general defeasible theories through the use of a pre-processing transformation which eliminates all uses of defeaters and superiority relations.
PED is a dialogue management system that uses a probabilistic nested belief model to choose dialogue strategies. The dialogue system designer need only supply a set of plan rules to PED as a dialogue grammar with preconditions. Using this grammar, PED constructs game trees (like the one below) to represent the outcomes of the dialogue, so that a dialogue strategy can be chosen for the current turn in the dialogue. PED automatically maintains a belief model by a belief revision process that uses the observed acts in the dialogue. The game tree is evaluated in the context of this belief model. PED is efficient because it uses probabilistic estimates of belief rather than a plain logical belief model.