Names of functions are located in the package
|queens (backtracking search), queens2 (local search)||backtrack, specialization of added-assumption, assume-slot-values|
(Sudoku puzzle generator and solver)
|sugen (local search), susolve (backtracking search)||backtrack, specialization of order-control-disjunction and added-assumption, specialization of validate-combination, assume-slot-values|
|Planning||miss.lisp (missionaries-and-cannibals problem)||miss||solutions, non-monotonic reasoning, :assume qualifier, :count slot option, assume-slot-values|
|blocks.lisp (blocks world)||blocks||solutions, non-monotonic reasoning, :assume qualifier, :count slot option, :inverse slot option, assume-slot-values|
|Multiple-Fault Diagnosis||mult.lisp||diagnoses1, diagnoses2||solutions, non-monotonic reasoning, constraints, composite objects|
|Counterfactuals||boris.lisp||if-boris||solutions, non-monotonic reasoning, :assume qualifier|
|Temporal Reasoning||career.lisp||career1, career2||solutions, non-monotonic reasoning, :assume qualifier, :count slot option, composite objects|
Non-monotonic (or defeasible) reasoning is the the norm in practical, everyday problem-solving: it is reasoning under conditions of uncertainty, from incomplete or unreliable information. Such inferences do not carry a guarantee of soundness and may later need to be revised.
The temporal reasoning demonstration clearly illustrates this phenomenon. Assimilating a hiring or promotion event may result in a revision of a inference about a person's employment status made from their employment history.
The ATMS is used to realize non-monotonic reasoning by entirely extra-logical means.
The counterfactuals demonstration concerns statements of the form ‘if such-and-such were the case, then such-and-such would be the case’. It employs a treatment of such statements not simply as implicational rules whose antecedent happens to be false, but as elliptical arguments. One counterfactual can be defeated by another: they sanction conclusions which may be contradicted by subsequently-acquired information.
Diagnosis is also non-monotonic in the sense that different diagnoses may result from an additional observation of the faulty system's behaviour.
The planning demonstrations illustrate the formulation of the actions relevant to (e.g.) a simple ‘blocks world’ problem as axioms whose consequent contradicts their antecedent. The law of contradiction is used to construct a new situation or possible world, given by a set of statements (i.e., slot values), comprising the consequent and all features of a previous situation that are consistent with it: information is ‘carried over’ from one situation to another in the absence of knowledge to the contrary.