Grup de Recerca en Intel·ligència Artificial (INSPIRES)
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The Artificial Intelligence Research Group of the University of Lleida is formed by members of the Department of Computer Science. The current research of the group focus on the following areas: Argumentation: logical formalizations, technological applications, and integration with fuzzy logic programming languages. Constraint Programming: modelling, practical complexity, distributed CSP, weighted CSP, and connections with satisfiability. Fuzzy logic programming: integration of logic propramming languages and fuzzy logics and formalisms for treatment of uncertainty, such as possibilistic logic. Manyvalued logics: logical calculi for signed CNF formula, complexity, automated theorem proving. Satisfiability: design, analysis, implementation and evaluation of algorithms for solving SAT, MaxSAT and QBF for both Boolean and ManyValued CNF formulas, efficient encodings, logical calculi, tractable problems, phase transitions, local search, learning. [Més informació]
Recent Submissions

ArgumentBased Expansion Operators in Possibilistic Defeasible Logic Programming: Characterization and Logical Properties
(Springer Verlag, 2005)Possibilistic Defeasible Logic Programming (PDeLP) is a logic programming language which combines features from argumentation theory and logic programming, incorporating as well the treatment of possibilistic uncertainty ... 
Modelling Power and Trust for Knowledge Distribution: An Argumentative Approach
(Springer Verlag, 2005)Knowledge and Information distribution, which is one of the main processes in Knowledge Management, is greatly affected by power explicit relations, as well as by implicit relations like trust. Making decisions about ... 
Computing Dialectical Trees Efficiently in Possibilistic Defeasible Logic Programming
(Springer Verlag, 2005)Possibilistic Defeasible Logic Programming (PDeLP) is a logic programming language which combines features from argumentation theory and logic programming, incorporating as well the treatment of possibilistic uncertainty ... 
Statistical Regimes Across Constrainedness Regions
(Springer Verlag, 2005)Much progress has been made in terms of boosting the effectiveness of backtrack style search methods. In addition, during the last decade, a much better understanding of problem hardness, typical case complexity, and ... 
Knowledge Distribution in Large Organizations Using Defeasible Logic Programming
(Springer Verlag, 2005)Distributing pieces of knowledge in large, usually distributed organizations is a central problem in Knowledge and Organization Management. Policies for distributing knowledge and information are very often incomplete, ... 
An ArgumentBased Framework to Model an Agent’s Beliefs in a Dynamic Environment
(Springer Verlag, 2005)One of the most difficult problems in multiagent systems involves representing knowledge and beliefs of agents in dynamic environments. New perceptions modify an agent’s current knowledge about the world, and consequently ... 
Exploiting Unit Propagation to Compute Lower Bounds in Branch and Bound MaxSAT Solvers
(Springer Verlag, 2005)One of the main differences between complete SAT solvers and exact MaxSAT solvers is that the former make an intensive use of unit propagation at each node of the proof tree while the latter, in order to ensure optimality, ... 
Improved Exact Solvers for Weighted MaxSAT
(Springer Verlag, 2005)We present two new branch and bound weighted MaxSAT solvers (Lazy and Lazy ) which incorporate original data structures and inference rules, and a lower bound of better quality 
Communication and Computation in Distributed CSP Algorithms
(Springer Verlag, 2005)We introduce SensorDCSP, a naturally distributed benchmark based on a realworld application that arises in the context of networked distributed systems. In order to study the performance of Distributed CSP (DisCSP) ... 
Sensor networks and distributed CSP: communication, computation and complexity
(Elsevier, 2005)We introduce SensorDCSP, a naturally distributed benchmark based on a realworld application that arises in the context of networked distributed systems. In order to study the performance of Distributed CSP (DisCSP) ... 
A MaxSAT Solver with Lazy Data Structures
(Springer Verlag, 2004)We present a new branch and bound algorithm for MaxSAT which incorporates original lazy data structures, a new variable selection heuristics and a lower bound of better quality. We provide experimental evidence that ... 
New Inference Rules for MaxSAT
(Association for the Advancement of Artificial Intelligence, 2007)Exact MaxSAT solvers, compared with SAT solvers, apply little inference at each node of the proof tree. Commonly used SAT inference rules like unit propagation produce a simplified formula that preserves satisfiability ... 
Argumentbased critics and recommenders: A qualitative perspective on user support systems
(Elsevier, 2006)In recent years we have witnessed the widespread evolution of support tools that operate in association with the user to accomplish a range of computermediated tasks. Two examples of these tools are critics and recommenders. ... 
Exact MaxSAT solvers for overconstrained problems
(Springer Verlag, 2006)We present a new generic problem solving approach for overconstrained problems based on MaxSAT. We first define a Boolean clausal form formalism, called soft CNF formulas, that deals with blocks of clauses instead of ... 
Argumentation and the Dynamics of Warranted Beliefs in Changing Environments
(Springer Verlag, 2005)One of the most difficult problems in MultiAgent Systems (MAS) involves representing the knowledge and beliefs of an agent which performs its tasks in a dynamic environment. New perceptions modify this agent’s current ... 
Exploiting multivalued knowledge in variable selection heuristics for SAT solvers
(Springer Verlag, 2007)We show that we can design and implement extremely efficient variable selection heuristics for SAT solvers by identifying, in Boolean clause databases, sets of Boolean variables that model the same multivalued variable ... 
Improved Branch and Bound Algorithms for Max2SAT and Weighted Max2SAT
(Springer Verlag, 2003)We developed novel branch and bound algorithms for solving MaxSAT and weighted MaxSAT, which are variants of the algorithm of Borchers & Furman (BFA) [1]. We improved BFA by (i) defining a lower bound of better quality, ... 
Adding truthconstants to logics of continuous tnorms: Axiomatization and completeness results
(Elsevier, 2007)In this paper we study generic expansions of logics of continuous tnorms with truthconstants, taking advantage of previous results for Łukasiewicz logic and more recent results for Gödel and Product logics. Indeed, we ... 
Minimal and Redundant SAT Encodings for the AllIntervalSeries Problem
(Springer Verlag, 2002)The SAT encodings defined so far for the allintervalseries (ais) problem are very hard for local search but rather easy for systematic algorithms. We define different SAT encodings for the ais problem and provide ... 
RegularSAT: A manyvalued approach to solving combinatorial problems
(Elsevier, 2007)RegularSAT is a constraint programming language between CSP and SAT that—by combining many of the good properties of each paradigm—offers a good compromise between performance and expressive power. Its similarity to SAT ...