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299
Complexity and Expressive Power of Logic Programming
, 1997
"... This paper surveys various complexity results on different forms of logic programming. The main focus is on decidable forms of logic programming, in particular, propositional logic programming and datalog, but we also mention general logic programming with function symbols. Next to classical results ..."
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Cited by 365 (57 self)
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This paper surveys various complexity results on different forms of logic programming. The main focus is on decidable forms of logic programming, in particular, propositional logic programming and datalog, but we also mention general logic programming with function symbols. Next to classical results on plain logic programming (pure Horn clause programs), more recent results on various important extensions of logic programming are surveyed. These include logic programming with different forms of negation, disjunctive logic programming, logic programming with equality, and constraint logic programming. The complexity of the unification problem is also addressed.
Unlocking the mask: A look at the process by which authentic leaders impact follower attitudes and behaviors,
 Leadership Quarterly,
, 2004
"... Abstract The conceptual and empirical links between authentic leadership and follower attitudes, behaviors, and performance outcomes have not been fully developed. Although we have a number of articles developing the theory of authentic leadership and testing propositions that will appear in a fort ..."
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Cited by 103 (9 self)
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Abstract The conceptual and empirical links between authentic leadership and follower attitudes, behaviors, and performance outcomes have not been fully developed. Although we have a number of articles developing the theory of authentic leadership and testing propositions that will appear in a forthcoming special issue of The Leadership Quarterly (Vol. 16, Issue 3, 2005), the focus of this article is to provide some of the initial foundation work for the broader theoretical framework of how authentic leaders influence follower attitudes, behaviors, and performance. Here, we draw from positive organizational behavior, trust, hope, emotion, identification, and identity theories to describe the processes by which authentic leaders exert their influence on followers' attitudes and behaviors. Research propositions based on the proposed theoretical model and implications for future theory building and research are presented.
Towards a Declarative Query and Transformation Language for XML and Semistructured Data: Simulation Unification
, 2002
"... The growing importance of XML as a data interchange standard demands languages for data querying and transformation. Since the mid 90es, several such languages have been proposed that are inspired from functional languages (such as XSLT [1]) and/or database query languages (such as XQuery [2]). ..."
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Cited by 92 (37 self)
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The growing importance of XML as a data interchange standard demands languages for data querying and transformation. Since the mid 90es, several such languages have been proposed that are inspired from functional languages (such as XSLT [1]) and/or database query languages (such as XQuery [2]). This paper addresses applying logic programming concepts and techniques to designing a declarative, rulebased query and transformation language for XML and semistructured data.
Tractable Query Answering and Rewriting under Description Logic Constraints
 Journal of Applied Logic
"... Abstract. Answering queries over an incomplete database w.r.t. a set of constraints is an important computational task with applications in fields as diverse as information integration and metadata management in the Semantic Web. Description Logics (DL) are constraint languages that have been extens ..."
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Cited by 62 (9 self)
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Abstract. Answering queries over an incomplete database w.r.t. a set of constraints is an important computational task with applications in fields as diverse as information integration and metadata management in the Semantic Web. Description Logics (DL) are constraint languages that have been extensively studied in the past with the goal of providing useful modeling constructs while keeping the query answering problem decidable. For many DLs, query answering under constraints can be reduced to query rewriting: given a conjunctive query Q and a set of DL constraints T, the query Q can be transformed into a datalog query QT that takes into account the semantic consequences of T; then, to obtain answers to Q w.r.t. T and some (arbitrary) database instance A, one can simply evaluate QT over A using existing (deductive) database technology, without taking T into account. In this paper, we present a novel query rewriting algorithm that handles constraints modeled in the DL ELHIO ¬ and use it to show that answering conjunctive queries in this setting is PTimecomplete w.r.t. data complexity. Our algorithm deals with various description logics of the EL and DLLite families and is worstcase optimal w.r.t. data complexity for all of them. 1
The psychological capital of Chinese workers: Exploring the relationship with performance
 Management and Organization Review
, 2005
"... abstract Everyone knows about China’s huge population and the fastgrowing economy. Although macrolevel sociological and economic analyses have given some attention to the linkage between the two, at the micro level, the relationship between human resources and, more specifically, psychological cap ..."
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Cited by 58 (8 self)
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abstract Everyone knows about China’s huge population and the fastgrowing economy. Although macrolevel sociological and economic analyses have given some attention to the linkage between the two, at the micro level, the relationship between human resources and, more specifically, psychological capital of Chinese workers and their performance has been largely ignored. Within the context of three factories (two private and one stateowned) in the People’s Republic of China, this exploratory study examined the relationship of a sample (n = 422) of Chinese workers ’ positive psychological capital states and their performance. Results indicated the workers’ positive states of hope, optimism, and resiliency, separately and when the three were combined into a core construct of psychological capital, significantly correlated with their performance, as rated by their supervisors. An analysis of workers in one of the factories (n = 272) also found a significant relationship between the workers ’ positive psychological capital and the performance outcome of relative meritbased salary. Limitations, future research, and practical implications conclude the article.
Solving quantified verification conditions using satisfiability modulo theories
 In CADE
, 2007
"... Abstract. First order logic provides a convenient formalism for describing a wide variety of verification conditions. Two main approaches to checking such conditions are pure first order automated theorem proving (ATP) and automated theorem proving based on satisfiability modulo theories (SMT). Trad ..."
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Cited by 51 (7 self)
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Abstract. First order logic provides a convenient formalism for describing a wide variety of verification conditions. Two main approaches to checking such conditions are pure first order automated theorem proving (ATP) and automated theorem proving based on satisfiability modulo theories (SMT). Traditional ATP systems are designed to handle quantifiers easily, but often have difficulty reasoning with respect to theories. SMT systems, on the other hand, have builtin support for many useful theories, but have a much more difficult time with quantifiers. One clue on how to get the best of both worlds can be found in the legacy system Simplify which combines builtin theory reasoning with quantifier instantiation heuristics. Inspired by Simplify and motivated by a desire to provide a competitive alternative to ATP systems, this paper describes a methodology for reasoning about quantifiers in SMT systems. We present the methodology in the context of the Abstract DPLL Modulo Theories framework. Besides adapting many of Simplify’s techniques, we also introduce a number of new heuristics. Most important is the notion of instantiation level which provides an effective mechanism for prioritizing and managing the large search space inherent in quantifier instantiation techniques. These techniques have been implemented in the SMT system CVC3. Experimental results show that our methodology enables CVC3 to solve a significant number of benchmarks that were not solvable with any previous approach. 1
Type Dependencies for Logic Programs using ACIunification
 In Proceedings of the 1996 Israeli Symposium on Theory of Computing and Systems
, 1996
"... This paper presents a new notion of typing for logic programs which generalizes the notion of directional types. The generation of type dependencies for a logic program is fully automatic with respect to a given domain of types. The analysis method is based on a novel combination of program abstract ..."
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Cited by 44 (8 self)
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This paper presents a new notion of typing for logic programs which generalizes the notion of directional types. The generation of type dependencies for a logic program is fully automatic with respect to a given domain of types. The analysis method is based on a novel combination of program abstraction and ACIunification which is shown to be correct and optimal. Type dependencies are obtained by abstracting programs, replacing concrete terms by their types, and evaluating the meaning of the abstract programs using a standard semantics for logic programs enhanced by ACIunification. This approach is generic and can be used with any standard semantics. The method is both theoretically clean and easy to implement using general purpose tools. The proposed domain of types is condensing which means that analyses can be carried out in both topdown or bottomup frameworks with no loss of precision for goalindependent analyses. The proposed method has been fully implemented within a bottomup approach and the experimental results are promising.
Unions of NonDisjoint Theories and Combinations of Satisfiability Procedures
 THEORETICAL COMPUTER SCIENCE
, 2001
"... In this paper we outline a theoretical framework for the combination of decision procedures for constraint satisfiability. We describe a general combination method which, given a procedure that decides constraint satisfiability with respect to a constraint theory T1 and one that decides constraint s ..."
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Cited by 44 (7 self)
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In this paper we outline a theoretical framework for the combination of decision procedures for constraint satisfiability. We describe a general combination method which, given a procedure that decides constraint satisfiability with respect to a constraint theory T1 and one that decides constraint satisfiability with respect to a constraint theory T2, produces a procedure that (semi)decides constraint satisfiability with respect to the union of T1 and T2. We provide a number of modeltheoretic conditions on the constraint language and the component constraint theories for the method to be sound and complete, with special emphasis on the case in which the signatures of the component theories are nondisjoint. We also describe some general classes of theories to which our combination results apply, and relate our approach to some of the existing combination methods in the field.
Symbolic protocol analysis with products and DiffieHellman exponentiation
, 2003
"... We demonstrate that for any welldefined cryptographic protocol, the symbolic trace reachability problem in the presence of an Abelian group operator (e.g., multiplication) can be reduced to solvability of a decidable system of quadratic Diophantine equations. This result enables complete, fully aut ..."
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Cited by 41 (0 self)
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We demonstrate that for any welldefined cryptographic protocol, the symbolic trace reachability problem in the presence of an Abelian group operator (e.g., multiplication) can be reduced to solvability of a decidable system of quadratic Diophantine equations. This result enables complete, fully automated formal analysis of protocols that employ primitives such as DiffieHellman exponentiation, multiplication, andxor, with a bounded number of role instances, but without imposing any bounds on the size of terms created by the attacker. 1