• Publications
  • Influence
State-Variable Planning Under Structural Restrictions: Algorithms and Complexity
This work identifies restrictions on the underlying state-transition graph which can tractably be tested and presents a planning algorithm which is correct and runs in polynomial time under these restrictions, and presents an exhaustive map of the complexity results for planning under all combinations of four previously studied syntactical restrictions and five new structural restrictions. Expand
Some Results on the Complexity of Planning with Incomplete Information
The main result of this paper is that the non-branching plan existence problem in unobservable domains with an expressive operator formalism is EXPSPACE-complete. Expand
A Complete Classification of Tractability in RCC-5
This work investigates the computational properties of the spatial algebra RCC-5 which is a restricted version of the RCC framework for spatial reasoning and identifies all maximal tractable subalgebras which are four in total. Expand
Reasoning about temporal relations: The tractable subalgebras of Allen's interval algebra
This article provides the final step in the classification of complexity for satisfiability problems over constraints expressed in Allen's interval algebra, and shows that this algebra contains exactly eighteen maximal tractable subalgebras, and reasoning in any fragment not entirely contained in one of these subalagbras is NP-complete. Expand
Planning with Reduced Operator Sets
It is demonstrated that some state-of-the-art planners run faster using reduced operator sets, a conjecture that the search for a plan would be more efficient if there were only a small number of paths from the initial state to the goal state. Expand
Point algebras for temporal reasoning: Algorithms and complexity
A new time model suitable for reasoning about systems with a bounded number of unsynchronized clocks is presented, connections with spatial reasoning are investigated, and improved algorithms for deciding satisfiability of the tractable point algebras are presented. Expand
An algorithm for counting maximum weighted independent sets and its applications
We present an O(1.3247n) algorithm for counting the number of independent sets with maximum weight in graphs. We show how this algorithm can be used solving a number of different counting problems:Expand
Tractable plan existence does not imply tractable plan generation
A provably sound and complete incremental planner is proposed, i.e., a planner that can usually output an executable prefix of the final plan before it has generated the whole plan. Expand
The complexity of counting homomorphisms seen from the other side
It is proved (under a weaker complexity-theoretic assumption) that the corresponding counting problem HOM(C, _) is solvable in polynomial time if and only if all structures in C have bounded tree-width. Expand
Counting models for 2SAT and 3SAT formulae
This work provides an algorithm for the restricted case of separable 2SAT formulae, with fast running times for well-studied input classes, and develops new measures of formula complexity, allowing us to conveniently analyze the effects of certain factors with a large impact on the total running time. Expand