Phan Duc Tu

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Answer Sets for Logic Programs with Arbitrary Abstract Constraint Atoms

Journal of Artificial Intelligence Research, 2007

In this paper, we present two alternative approaches to defining answer sets for logic programs w... more In this paper, we present two alternative approaches to defining answer sets for logic programs with arbitrary types of abstract constraint atoms (c-atoms). These approaches generalize the fixpoint-based and the level mapping based answer set semantics of normal logic programs to the case of logic programs with arbitrary types of c-atoms. The results are four different answer set definitions which are equivalent when applied to normal logic programs. The standard fixpoint-based semantics of logic programs is generalized in two directions, called answer set by reduct and answer set by complement. These definitions, which differ from each other in the treatment of negation-as-failure (naf) atoms, make use of an immediate consequence operator to perform answer set checking, whose definition relies on the notion of conditional satisfaction of c-atoms w.r.t. a pair of interpretations. The other two definitions, called strongly and weakly well-supported models, are generalizations of the ...

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An approximation of action theories of AC and its application to conformant planning

Lecture Notes in Computer Science, 2005

Techniques for Data Aggregation, Analysis, and Distribution

Sensing and NonDeterministic Actions in Domains with Multi-Valued Fluents

Developing Agents for Bioinformatics Applications: A Preliminary Design

Parallel and Distributed Processing Techniques and Applications, 2003

CPP: A Constraint Logic Programming Based Planner with Preferences

Lecture Notes in Computer Science

We describe the development of a constraint logic programming based system, called CPP, which is ... more

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The Impact of Personal Relationships on Bribery Incidence in Transition Economies

European Management Review, 2014

Prior work on corruption has largely overlooked personal relationships as an essential determinan... more Prior work on corruption has largely overlooked personal relationships as an essential determinant of bribery incidence in transition economies. In these countries, relationships with public officials are instrumental in enabling transactions and lowering transaction costs, due to incoherent and ever-changing business regulations. Our study examines the impact of personal relationships on bribery incidence in Vietnam, finding that relationships with central government officials decreases the likelihood of bribery, while relationships with local government officials increases the likelihood of bribery. The results provide convincing support for the alleged importance of public-private relationships in contemporary transition economies.

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GenerIE: Information extraction using database queries

2010 IEEE 26th International Conference on Data Engineering (ICDE 2010), 2010

Information extraction systems are traditionally implemented as a pipeline of special-purpose pro... more Information extraction systems are traditionally implemented as a pipeline of special-purpose processing modules. A major drawback of such an approach is that whenever a new extraction goal emerges or a module is improved, extraction has to be reapplied from scratch to the entire text corpus even though only a small part of the corpus might be affected. In this demonstration proposal, we describe a novel paradigm for information extraction: we store the parse trees output by text processing in a database, and then express extraction needs using queries, which can be evaluated and optimized by databases. Compared with the existing approaches, database queries for information extraction enable generic extraction and minimize reprocessing. However, such an approach also poses a lot of technical challenges, such as language design, optimization and automatic query generation. We will present the opportunities and challenges that we met when building GenerIE, a system that implements this paradigm.

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Planning with Sensing Actions and Incomplete Information Using Logic Programming

Logic Programming and Nonmonotonic Reasoning, 2003

We present a logic programming based conditional planner that is capable of generating both condi... more We present a logic programming based conditional planner that is capable of generating both conditional plans and conformant plans in the presence of sensing actions and incomplete information. We prove the correctness of our implementation and show that our planner is complete with respect to the 0approximation of sensing actions and the class of conditional plans considered in this paper. Finally, we present preliminary experimental results and discuss further enhancements to the program.

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Reasoning and planning with sensing actions, incomplete information, and static causal laws using answer set programming

Theory and Practice of Logic Programming, 2007

We extend the 0-approximation of sensing actions and incomplete information in Son and Baral (200... more We extend the 0-approximation of sensing actions and incomplete information in Son and Baral (2001) to action theories with static causal laws and prove its soundness with respect to the possible world semantics. We also show that the conditional planning problem with respect to this approximation isNP-complete. We then present an answer set programming based conditional planner, called ASCP, that is capable of generating both conformant plans and conditional plans in the presence of sensing actions, incomplete information about the initial state, and static causal laws. We prove the correctness of our implementation and argue that our planner is sound and complete with respect to the proposed approximation. Finally, we present experimental results comparing ASCP to other planners.

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Construction of an Agent-Based Framework for Evolutionary Biology: A Progress Report

Lecture Notes in Computer Science, 2005

We report on the development of an agent-based system, called ΦLOG, for the specification and exe... more We report on the development of an agent-based system, called ΦLOG, for the specification and execution of phylogenetic inference applications. We detail the implementation of the main components of the system. In the process, we discuss how advanced techniques developed in different research areas such as domain-specific languages, planning, Web services discovery and invocation, and Web services composition can be applied in the building of the ΦLOG system. Compiler Configuration Component Planning Execution Monitoring

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Efficient Reasoning About Action and Change in the Presence of Incomplete Information and Its Application in Planning

Logic Programming, 2006

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Executing Action Languages for Planning Problems on Multi-core Platforms: Some Preliminary Results

cs.nmsu.edu

The goal of this paper is to demonstrate that parallel programming techniques can boost AI planni... more The goal of this paper is to demonstrate that parallel programming techniques can boost AI planning systems in various aspects. It shows that an appropriate parallelization of a sequential planning system often brings gain in performance and/or scalability. We start by describing general schemes for parallelizing the construction of a plan. We then discuss the applications of these techniques to two domain-independent heuristic search based planners-a competitive conformant planner (CPA) and a state-of-the-art classical planner (FF). We present experimental results which show that performance improvements and scalability are obtained in both cases. Finally, we discuss the issues that should be taken into consideration when designing a parallel planning system and relate our work to the existing literature.

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Reasoning about Sensing Actions in Domains with Multi-Valued Fluents

Studia Logica, 2005

In this paper, we discuss the weakness of current action languages for sensing actions with respe... more In this paper, we discuss the weakness of current action languages for sensing actions with respect to modeling domains with multi-valued fluents. To address this problem, we propose a language with sensing actions and multi-valued fluents, called AMK , provide a transition function based semantics for the language, and demonstrate its use through several examples from the literature. We then define the entailment relationship between action theories and queries in AM K , denoted by |= AM K , and discuss some properties about AMK .

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Incremental Information Extraction Using Relational Databases

IEEE Transactions on Knowledge and Data Engineering, 2012

Information extraction systems are traditionally implemented as a pipeline of special-purpose pro... more Information extraction systems are traditionally implemented as a pipeline of special-purpose processing modules targeting the extraction of a particular kind of information. A major drawback of such an approach is that whenever a new extraction goal emerges or a module is improved, extraction has to be reapplied from scratch to the entire text corpus even though only a small part of the corpus might be affected. In this paper, we describe a novel approach for information extraction in which extraction needs are expressed in the form of database queries, which are evaluated and optimized by database systems. Using database queries for information extraction enables generic extraction and minimizes reprocessing of data by performing incremental extraction to identify which part of the data is affected by the change of components or goals. Furthermore, our approach provides automated query generation components so that casual users do not have to learn the query language in order to perform extraction. To demonstrate the feasibility of our incremental extraction approach, we performed experiments to highlight two important aspects of an information extraction system: efficiency and quality of extraction results. Our experiments show that in the event of deployment of a new module, our incremental extraction approach reduces the processing time by 89.64 percent as compared to a traditional pipeline approach. By applying our methods to a corpus of 17 million biomedical abstracts, our experiments show that the query performance is efficient for real-time applications. Our experiments also revealed that our approach achieves high quality extraction results.

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Which Entrepreneurs Bribe and what do they Get from It? Exploratory Evidence from Vietnam

Entrepreneurship Theory and Practice, 2010

This article investigates whether bribery in emerging economies matters and whether such bribery ... more This article investigates whether bribery in emerging economies matters and whether such bribery has a diminishing return to performance. Bribery allows entrepreneurs to develop and foster a network of informal relationships with public officials, and reap the accompanying benefits; but it may also have disadvantages, such as an inefficient allocation of resources. The relationship between bribery and performance was estimated using unique data derived from a survey of 606 Vietnamese entrepreneurs. We controlled for various entrepreneurial, organizational, and industrial characteristics. The exploratory results provide support for a hill–shaped non–monotonic relationship between bribery and revenues.

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An extension to conformant planning using logic programming

Proceedings of the 20th international joint …, 2007

In this paper we extend the logic programming based conformant planner described in [Son et al., ... more

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Approximation of action theories and its application to conformant planning

Artificial Intelligence, 2011

This paper describes our methodology for building conformant planners, which is based on recent a... more This paper describes our methodology for building conformant planners, which is based on recent advances in the theory of action and change and answer set programming. The development of a planner for a given dynamic domain starts with encoding the knowledge about fluents and actions of the domain as an action theory D of some action language. Our choice in this paper is AL-an action language with dynamic and static causal laws and executability conditions. An action theory D of AL defines a transition diagram T (D) containing all the possible trajectories of the domain. A transition s, a, s belongs to T (D) iff the execution of the action a in the state s may move the domain to the state s. The second step in the planner development consists in finding a deterministic transition diagram T lp (D) such that nodes of T lp (D) are partial states of D, its arcs are labeled by actions, and a path in T lp (D) from an initial partial state δ 0 to a partial state satisfying the goal δ f corresponds to a conformant plan for δ 0 and δ f in T (D). The transition diagram T lp (D) is called an 'approximation' of T (D). We claim that a concise description of an approximation of T (D) can often be given by a logic program π(D) under the answer sets semantics. Moreover, complex initial situations and constraints on plans can be also expressed by logic programming rules and included in π(D). If this is possible then the problem of finding a parallel or sequential conformant plan can be reduced to computing answer sets of π(D). This can be done by general purpose answer set solvers. If plans are sequential and long then this method can be too time consuming. In this case, π(D) is used as a specification for a procedural graph searching conformant planning algorithm. The paper illustrates this methodology by building several conformant planners which work for domains with complex relationship between the fluents. The efficiency of the planners is experimentally Preprint submitted to Elsevier Science evaluated on a number of new and old benchmarks. In addition we show that for a subclass of action theories of AL our planners are complete, i.e., if in T lp (D) we cannot get from δ 0 to a state satisfying the goal δ f then there is no conformant plan for δ 0 and δ f in T (D).

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On the completeness of approximation based reasoning and planning in action theories with incomplete information

Proc. 10th Int. Conf. on Principles of KR and Reasoning …, 2006

In this paper, we study the completeness of the 0-approximation for action theories with incomple... more

Conformant planning for domains with constraints-a new approach

PROCEEDINGS OF THE …, 2005

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