Hudson Turner

Nonmonotonic causal theories

The nonmonotonic causal logic defined in this paper can be used to represent properties of actions, including actions with conditional and indirect effects, nondeterministic actions, and concurrently executed actions. It has been applied to several challenge problems in the theory of commonsense knowledge. We study the relationship between this formalism and other work on nonmonotonic reasoning and knowledge representation, and discuss its implementation, called the Causal Calculator.

Nested expressions in logic programs

We extend the answer set semantics to a class of logic programs with nested expressions permitted in the bodies and heads of rules. These expressions are formed from literals using negation as failure, conjunction (,) and disjunction (;) that can be nested arbitrarily. Conditional expressions are introduced as abbreviations. The study of equivalent transformations of programs with nested expressions shows that any such program is equivalent to a set of disjunctive rules, possibly with negation as failure in the heads. The generalized answer set semantics is related to the Lloyd–Topor generalization of Clark’s completion and to the logic of minimal belief and negation as failure.

Strong equivalence made easy: nested expressions and weight constraints

Logic programs

Representing actions in logic programs and default theories : A situation calculus approach

P

A logic of universal causation

and

Representing Transition Systems by Logic Programs

Q

Polynomial-Length Planning Spans the Polynomial Hierarchy

are strongly equivalent if, given any program

Update by means of inference rules

R

From Disjunctive Programs to Abduction

, programs

Order-consistent programs are cautiously monotonic

P \cup R