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On Tractable Cases of Target Set Selection
"... We study the NPcomplete TARGET SET SELECTION (TSS) problem occurring in social network analysis. Complementing results on its approximability and extending results for its restriction to trees and bounded treewidth graphs, we classify the influence of the parameters “diameter”, “cluster edge delet ..."
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Cited by 7 (3 self)
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deletion number”, “vertex cover number”, and “feedback edge set number ” of the underlying graph on the problem’s complexity, revealing both tractable and intractable cases. For instance, even for diametertwo split graphs TSS remains very hard. TSS can be efficiently solved on graphs with small feedback
Answering Queries: Tractable Cases and Optimizations
, 2001
"... Answering queries is computationally very expensive, and many approaches have been proposed in the literature to face this fundamental problem. Some of them are based on optimization modules that exploit quantitative information on the database instance, while other approaches exploit structural pro ..."
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Cited by 1 (1 self)
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properties of the query hypergraph. For instance, acyclic queries can be answered in polynomial time, and also query containment is efficiently decidable for acyclic queries. In this report, we review both quantitative and structural methods for optimizing query answering and identifying tractable classes
On some tractable cases of logical filtering
 In Proc. International Conference on Automated Planning and Scheduling (ICAPS
, 2006
"... Filtering denotes any method whereby an agent updates its belief state—its knowledge of the state of the world—from a sequence of actions and observations. In logical filtering, the belief state is a logical formula describing the possible world states. Efficient algorithms for logical filtering b ..."
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Cited by 3 (2 self)
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Filtering denotes any method whereby an agent updates its belief state—its knowledge of the state of the world—from a sequence of actions and observations. In logical filtering, the belief state is a logical formula describing the possible world states. Efficient algorithms for logical filtering bear important implications on reasoning tasks such as planning and diagnosis. In this paper, we will identify classes of transition constraints that are amenable to compact and indefinite filtering—presenting efficient algorithms wherever necessary. We will first show that connected rowconvex (CRC) constraints are amenable to efficient filtering when pathconsistency is enforced in appropriate steps. We will then extend this theory to provide a filtering algorithm based on repeatedly enforcing pathconsistency and embedding the domain values of the related variables in tree structures to guarantee global consistency. Finally, we will identify and comment on the problem of multiagent localization as a potential application of the theory developed in the paper (under some reasonable assumptions).
On Some Tractable Cases of Logical Filtering
"... Filtering denotes any method whereby an agent updates its belief state—its knowledge of the state of the world—from a sequence of actions and observations. In logical filtering, the belief state is a logical formula describing the possible world states. Efficient algorithms for logical filtering bea ..."
Abstract
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Filtering denotes any method whereby an agent updates its belief state—its knowledge of the state of the world—from a sequence of actions and observations. In logical filtering, the belief state is a logical formula describing the possible world states. Efficient algorithms for logical filtering bear important implications on reasoning tasks such as planning and diagnosis. In this paper, we will identify classes of transition constraints that are amenable to compact and indefinite filtering—presenting efficient algorithms wherever necessary. We will first show that connected rowconvex (CRC) constraints are amenable to efficient filtering when pathconsistency is enforced in appropriate steps. We will then extend this theory to provide a filtering algorithm based on repeatedly enforcing pathconsistency and embedding the domain values of the related variables in tree structures to guarantee global consistency. Finally, we will identify and comment on the problem of multiagent localization as a potential application of the theory developed in the paper (under some reasonable assumptions).
Causes and Explanations in the StructuralModel Approach: Tractable Cases
 IN PROC. EIGHTEENTH CONFERENCE ON UNCERTAINTY IN ARTIFICIAL INTELLIGENCE (UAI 2002
, 2002
"... In this paper, we continue our research on the algorithmic aspects of Halpern and Pearl's causes and explanations in the structuralmodel approach. To this end, we present new characterizations of weak causes for certain classes of causal models, which show that under suitable restrictions deci ..."
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Cited by 10 (3 self)
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deciding causes and explanations is tractable. To our knowledge, these are the first explicit tractability results for the structuralmodel approach.
Tractable Cases of the Extended Global Cardinality Constraint
, 2008
"... We study the consistency problem for extended global cardinality (EGC) constraints. An EGC constraint consists of a set X of variables, a set D of values, a domain D(x) ⊆ D for each variable x, anda“cardinality set ” K(d) of nonnegative integers for each value d. The problem is to instantiate each ..."
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Cited by 7 (1 self)
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between EGC constraints and general factors in graphs. This allows us to extend the known polynomialtime case to certain noninterval cardinality sets. Second we consider EGC constraints under restrictions in terms of the treewidth of the value graph (the bipartite graph representing variablevalue pairs
Causes and Explanations in the StructuralModel Approach: Tractable Cases
, 2002
"... In this paper, we continue our research on the algorithmic aspects of Halpern and Pearl's causes and explanations in the structuralmodel approach. To this end, we present new characterizations of weak causes for certain classes of causal models, which show that under suitable restrictions deci ..."
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deciding causes and explanations is tractable. To our knowledge, these are the first explicit tractability results for the structuralmodel approach.
Maximum betweenness centrality: approximability and tractable cases
 WALCOM: Algorithms and Computation
, 2011
"... The Maximum Betweenness Centrality problem (MBC) can be defined as follows. Given a graph find a kelement node set C that maximizes the probability of detecting communication between a pair of nodes s and t chosen uniformly at random. It is assumed that the communication between s and t is realize ..."
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The Maximum Betweenness Centrality problem (MBC) can be defined as follows. Given a graph find a kelement node set C that maximizes the probability of detecting communication between a pair of nodes s and t chosen uniformly at random. It is assumed that the communication between s and t is realized along a shortest s–t path which is, again, selected uniformly at random. The communication is detected if the communication path contains a node of C. Recently, Dolev et al. (2009) showed that MBC is NPhard and gave a (1−1/e)approximation using a greedy approach. We provide a reduction of MBC to Maximum Coverage that simplifies the analysis of the algorithm of Dolev et al. considerably. Our reduction allows us to obtain a new algorithm with the same approximation ratio for a (generalized) budgeted version of MBC. We provide tight examples showing that the analyses of both algorithms are best possible. Moreover, we prove that MBC is APXcomplete and provide an exact polynomialtime algorithm for MBC on tree graphs. 1
New Tractable Cases in Default Reasoning from Conditional Knowledge Bases
, 2000
"... . We present new tractable cases for default reasoning from conditional knowledge bases. In detail, we introduce qHorn conditional knowledge bases, which allow for a limited use of disjunction. We show that previous tractability results for "entailment, proper "entailment, and z and ..."
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. We present new tractable cases for default reasoning from conditional knowledge bases. In detail, we introduce qHorn conditional knowledge bases, which allow for a limited use of disjunction. We show that previous tractability results for "entailment, proper "entailment, and z
Default Reasoning from Conditional Knowledge Bases: Complexity and Tractable Cases
 Artif. Intell
, 2000
"... Conditional knowledge bases have been proposed as belief bases that include defeasible rules (also called defaults) of the form " ! ", which informally read as "generally, if then ." Such rules may have exceptions, which can be handled in different ways. A number of entailment ..."
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Cited by 19 (11 self)
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bases are plagued with intractability in all these fragments. We thus explore cases in which these semantics are tractable, and find that most of them enjoy this property on feedbackfree Horn conditional knowledge bases, which constitute a new, meaningful class of conditional knowledge bases
Results 1  10
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2,081