6877505
An Algorithm for SAT Above the Threshold
We study algorithms for finding satisfying assignments of randomly generated 3-SAT formula. In particular, we consider distributions of highly constrained formulas (that is, “above the threshold” formulas) restricted to satisfiable instances. We obtain positive algorithmic results, showing that such formulas can be solved in low exponential time.
10922325
Quantified Constraint Satisfaction and Bounded Treewidth
Because the constraint satisfaction problem (CSP) is in general intractable, restricted cases of the CSP that are polynomial-time tractable have been heavily sought after. One class of restrictions that has been studied are variable-based restrictions, which concern the interaction among variables. In this paper, we consider the quantified constraint satisfaction problem (QCSP), a framework more general than the CSP. We present a QCSP tractability result arising from variable-based restrictions by giving a polynomial time algorithm for certain classes of QCSP instances having bounded treewidth.
958592
Inverse Circumscription
Inverse (or identification) problems involve deciding whether or not an explicitly given set of data points have an implicit description, for instance, in the form of a constraint network. Such problems provide insight into the relationships among various representations of knowledge, which may have differing computational properties. This paper formalizes and studies the inverse circumscription problem, which (roughly speaking) is to decide, given a set of models, if there exists a formula whose circumscription describes the input set.
3121075
Parameterized Compilability
Compilability is a measure of how effectively compilation (or preprocessing) can be applied to knowledge bases specified in a particular knowledge representation formalism; the aim of compilation is to allow for efficient, on-line query processing. A theory of compilability has been established for organizing knowledge representation formalisms according to a scheme of "compilability classes", and bears strong analogies to the classical theory of complexity, which permits the organization of computational problems according to complexity classes. We develop a novel theory of compilability, called parameterized compilability, which incorporates the notion of parameterization as used in parameterized complexity and permits for refined analysis of compilability.
3576
Collapsibility and Consistency in Quantified Constraint Satisfaction
The concept of consistency has pervaded studies of the constraint satisfiction problem. We introduce two concepts, which are inspired by consistency, for the more general framework of the quantified constraint satisfaction problem (QCSP). We use these concepts to derive, in a uniform fashion, proofs of polynomial-time tractability and corresponding algorithms for certain cases of the QCSP where the types of allowed relations are restricted. We not only unify existing tractability results and algorithms, but also identify new classes of tractable QCSPs.
9351295
Looking Algebraically at Tractable Quantified Boolean Formulas
We make use of the algebraic theory that has been used to study the complexity of constraint satisfaction problems, to investigate tractable quantified boolean formulas. We present a pair of results: the first is a new and simple algebraic proof of the tractability of quantified 2-satisfiability; the second is a purely algebraic characterization of models for quantified Horn formulas that were given by Kleine Buning, Subramani, and Zhao, and described proof-theoretically.
9860639
Analysis of parallel algorithms for finding a maximal independent set in a random hypergraph
It is well known 9] that nding a maximal independent set in a graph is in class N C, and 10] that nding a maximal independent set in a hypergraph with xed dimension is in RN C. It is not known whether this latter problem remains in N C when the dimension is part of the input. We will study the problem when the problem instances are randomly chosen. It was shown in 6] that the expected running time of a simple parallel algorithm for nding the lexicographically rst maximal independent set (lfmis) in a random simple graph is logarithmic in the input size. In this paper, we will prove a generalization of this result. We show that if a random k-uniform hypergraph has vertex set f1; 2; : : : ; ng and its edges are chosen independently with probability p from the set of ? n k possible edges, then our algorithm nds the lfmis
14330906
Creating Context-Aware Software Agents
Sharing ontologies, sensing context and reasoning are crucial to the realization of context-aware software agents. This document de- scribes our efforts in using the Resource Description Framework (RDF) and Prolog Forward Chaining (Pfc) system to provide support for ontology sharing and reasoning in the CoolAgent Recommendation System (CoolAgent RS), a context-aware multi-agent system. We also describes the implementation of the CoolAgent RS document and cuisine recommendation services that provide tailored services by exploiting user's context.
1567676
Bringing order to the Web: automatically categorizing search results
We developed a user interface that organizes Web search results into hierarchical categories. Text classification algorithms were used to automatically classify arbitrary search results into an existing category structure on-the-fly. A user study compared our new category interface with the typical ranked list interface of search results. The study showed that the category interface is superior both in objective and subjective measures. Subjects liked the category interface much better than the list interface, and they were 50% faster at finding information that was organized into categories. Organizing search results allows users to focus on items in categories of interest rather than having to browse through all the results sequentially.
5323377
Visualizing the expertise space
Expertise management systems are being widely adopted in organizations to manage tacit knowledge embedded in employees' heads. These systems have successfully applied many information technologies developed in fields such as information retrieval and document management to support expertise information collection, processing, and distribution. In this paper, we investigate the potentials of applying visualization techniques to support exploration of an expertise space. We implemented two widely applied dimensionality reduction visualization techniques, the self-organizing map and multidimensional scaling; to generate expert map and expertise field map visualizations based on an expertise data set. Our proposed approach is generic for automatic mapping of expertise space of an organization, research field, scientific domain, etc. Our initial analysis on the visualization results indicated that the expert map and expertise field map captured useful underlying structures of the expertise space and had the potential to support more efficient and effective expertise information searching and browsing.
1872726
An analysis of image queries in the field of art history
This study investigates end-users’ image queries by comparing the features of the queries to those identified in previous studies by Enser and McGregor (1992), Jorgensen (1995), and Fidel (1997). Twenty-nine college students majoring in art history were recruited. They were required to finish a term paper including at least 20 images. The participants’ image queries were collected by preand postsearch questionnaires, and three human reviewers mapped these queries into the previously identified features. Enser and McGregor’s categories of Unique and Nonunique, and Jorgensen’s classes of Location, Literal Object, Art Historical Information, People, and People-Related Attributes received high degrees of matching by three reviewers. This finding can be applied to add more details to Enser and McGregor’s four categories (Unique, Nonunique, Unique with refiners, and Nonunique with refiners) and to regroup Jorgensen’s 12 classes of image attributes.