Technology
Reasoning about soft constraints and conditional preferences: complexity results and approximation techniques
Domshlak, Carmel, Rossi, Francesca, Venable, Kristen Brent, Walsh, Toby
Many real life optimization problems contain both hard and soft constraints, as well as qualitative conditional preferences. However, there is no single formalism to specify all three kinds of information. We therefore propose a framework, based on both CP-nets and soft constraints, that handles both hard and soft constraints as well as conditional preferences efficiently and uniformly. We study the complexity of testing the consistency of preference statements, and show how soft constraints can faithfully approximate the semantics of conditional preference statements whilst improving the computational complexity.
Circuit Complexity and Decompositions of Global Constraints
Bessiere, Christian, Katsirelos, George, Narodytska, Nina, Walsh, Toby
We show that tools from circuit complexity can be used to study decompositions of global constraints. In particular, we study decompositions of global constraints into conjunctive normal form with the property that unit propagation on the decomposition enforces the same level of consistency as a specialized propagation algorithm. We prove that a constraint propagator has a a polynomial size decomposition if and only if it can be computed by a polynomial size monotone Boolean circuit. Lower bounds on the size of monotone Boolean circuits thus translate to lower bounds on the size of decompositions of global constraints. For instance, we prove that there is no polynomial sized decomposition of the domain consistency propagator for the ALLDIFFERENT constraint.
Decompositions of All Different, Global Cardinality and Related Constraints
Bessiere, Christian, Katsirelos, George, Narodytska, Nina, Quimper, Claude-Guy, Walsh, Toby
We show that some common and important global constraints like ALL-DIFFERENT and GCC can be decomposed into simple arithmetic constraints on which we achieve bound or range consistency, and in some cases even greater pruning. These decompositions can be easily added to new solvers. They also provide other constraints with access to the state of the propagator by sharing of variables. Such sharing can be used to improve propagation between constraints. We report experiments with our decomposition in a pseudo-Boolean solver.
Surynek
Surynek, Pavel (Charles University in Prague)
A problem of path planning for multiple robots is addressed in this paper. A specific case of the problem with so called theta-like environment is studied. This case of the problem represent structurally the simplest solvable case and an eventual solving method for this case can be used as a building block for more general solving procedures. We propose a solving method for multi-robot path planning in theta-like environments that constructs a solution by composing it of the pre-calculated shortest solutions of certain sub-problems. This approach prefers short overall solutions. Moreover, we propose a new algorithm for pre-calculating shortest solutions of sub-problems - it is in fact an improvement of the IDA* algorithm. An experimental comparison of our methods with existing techniques is presented in the paper.
Extending Temporal Causal Graph for Diagnosis Problems
Belouaer, Lamia (computer science) | Bouzid, Maroua (Computer Science) | Mouhoub, Malek (Computer Science)
We propose a new approach for Temporal Diagnosis Problems. This approach is an extension of Bouzid and Ligeza's method for temporal diagnosis problems. In this latter work, the authors define a Temporal Causal Graph (TCG) where time delays are expressed as temporal instants. We extend the TCG by including two quantitative relations in order to handle temporal intervals. We call ExTCG this new model. Solving a temporal diagnosis problem represented by the ExTCG consists of finding all possible explanations. It is performed using a backtrack search algorithm. In many diagnosis applications, the generation of all possible explanations is not necessary. For this reason, we augment the ExTCG in order to consider the degree of causality between symptoms. We call weighted ExTCG this extended model. Solving it consists of finding the explanation having the highest probability to occur. Through a real world diagnosis application in medicine, we illustrate the weighted ExTCG and its corresponding solving algorithm.
A Generalized Heuristic for Can't Stop
Glenn, James R. (Loyola College in Maryland) | Aloi, Christian J. (Loyola College in Maryland)
Can't Stop is a jeopardy stochastic game played on an octagonal game board with four six-sided dice. Optimal strategies have been computed for some simplified versions of Can't Stop by employing retrograde analysis and value iteration combined with Newton's method. These computations result in databases that map game positions to optimal moves. Solving the original game, however, is infeasible with current techniques and technology. This paper describes the creation of heuristic strategies for solitaire Can't Stop by generalizing an existing heuristic and using genetic algorithms to optimize the generalized parameters. The resulting heuristics are easy to use and outperform the original heuristic by 19%. Results of the genetic algorithm are compared to the known optimal results for smaller versions of Can't Stop, and data is presented showing the relative insensitivity of the particular genetic algorithm used to the balance between reduced noise and increased population diversity.
Exploring Lexical Network Development in Second Language Learners
Crossley, Scott (Mississippi State University) | Boggess, Julian E. (Gene) (Mississippi State University) | Salsbury, Thomas L. (Washington State University)
This study explores how neural network models can simulate word production in second language (L2) learners. A neural network was trained to simulate L2 word production using a variety of word properties related to connectionist networks (hypernymy, polysemy, concreteness, and meaningfulness). The study demonstrates that a neural network can produce words to a similar degree as L2 learners. The findings are important for theories of L2 lexical growth and production.
Special Track on Artificial Intelligence Education
Neller, Todd (Gettysburg College)
The FLAIRS Artificial Intelligence (AI) Education special track is devoted to methods of teaching AI, providing a forum where AI educators from diverse institutional settings can share resources, innovations, and insights to advance the quality of AI education worldwide. Topics include, but are not limited to model assignments, course syllabi, software, or other curricular resources; implementation of the computing curricula 2001 intelligent systems area; AI classroom techniques or innovations for undergraduate or graduate instruction; intelligent applications for instruction of AI and assessment of such applications; the use of robots or other hands-on equipment for teaching AI; strategies for incorporating AI research into AI courses; strategies for encouraging wider student interest and participation in AI; and descriptions or case studies of successful class projects or other pedagogical experiences.
Lifting the Limitations in a Rule-based Policy Language
Lindsay, Alan (University of Strathclyde) | Fox, Maria (University of Strathclyde) | Long, Derek (University of Strathclyde)
The predicates that are used to encode a planning domain in PDDL often do not include concepts that are important for effectively reasoning about problems in the domain. In particular, the effectiveness of rule-based policies in a domain depend on the concepts that can be expressed in the language used to capture those policies. In this work we investigate complimenting planning domain descriptions with abstract concepts and methods for making distinctions between similar objects. We present an architecture that allows a rule-based policy to reason with these additional concepts, using them to reason over structures that the rules would not be able to reason over without support. We demonstrate that this is sufficient to allow a rule-based policy to provide control in benchmark domains with interesting structures and we argue that our architecture could allow control knowledge learners to learn policies that provide control in these domains.