Results 1  10
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12
Updating action domain descriptions
 in Proc. IJCAI
, 2005
"... How can an intelligent agent update her knowledge base about an action domain, relative to some conditions (possibly obtained from earlier observations)? We study this question in a formal framework for reasoning about actions and change, in which the meaning of an action domain description can be r ..."
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Cited by 24 (5 self)
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How can an intelligent agent update her knowledge base about an action domain, relative to some conditions (possibly obtained from earlier observations)? We study this question in a formal framework for reasoning about actions and change, in which the meaning of an action domain description can be represented by a directed graph whose nodes correspond to states and whose edges correspond to action occurrences. We define the update of an action domain description in this framework, and show among other results that a solution to this problem can be obtained by a divideandconquer approach in some cases. We also introduce methods to compute a solution and an approximate solution to this problem, and analyze the computational complexity of these problems. Finally, we discuss techniques to improve the quality of solutions. 1
Characterizing Strong Equivalence for Argumentation Frameworks
 cf2 Semantics Revisited. Proc. COMMA 2010
, 2010
"... Since argumentation is an inherently dynamic process, it is of great importance to understand the effect of incorporating new information into given argumentation frameworks. In this work, we address this issue by analyzing equivalence between argumentation frameworks under the assumption that the f ..."
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Cited by 23 (3 self)
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Since argumentation is an inherently dynamic process, it is of great importance to understand the effect of incorporating new information into given argumentation frameworks. In this work, we address this issue by analyzing equivalence between argumentation frameworks under the assumption that the frameworks in question are incomplete, i.e. further information might be added later to both frameworks simultaneously. In other words, instead of the standard notion of equivalence (which holds between two frameworks, if they possess the same extensions), we require here that frameworks F and G are also equivalent when conjoined with any further framework H. Due to the nonmonotonicity of argumentation semantics, this concept is different to (but obviously implies) the standard notion of equivalence. We thus call our new notion strong equivalence and study how strong equivalence can be decided with respect to the most important semantics for abstract argumentation frameworks. We also consider variants of strong equivalence in which we define equivalence with respect to the sets of arguments credulously (or skeptically) accepted, and restrict strong equivalence to augmentations H where no new arguments are raised.
Logical foundations of wellfounded semantics
 In P
, 2006
"... We propose a solution to a longstanding problem in the foundations of wellfounded semantics (WFS) for logic programs. The problem addressed is this: which (nonmodal) logic can be considered adequate for wellfounded semantics in the sense that its minimal models (appropriately defined) coincide ..."
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Cited by 8 (2 self)
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We propose a solution to a longstanding problem in the foundations of wellfounded semantics (WFS) for logic programs. The problem addressed is this: which (nonmodal) logic can be considered adequate for wellfounded semantics in the sense that its minimal models (appropriately defined) coincide with the partial stable models of a logic program? We approach this problem by identifying the HT 2 frames previously proposed by Cabalar to capture WFS as structures of a kind used by Došen to characterise a family of logics weaker than intuitionistic and minimal logic. We define a notion of minimal, total HT 2 model which we call partial equilibrium model. Since for normal logic programs these models coincide with partial stable models, we propose the resulting partial equilibrium logic as a logical foundation for wellfounded semantics. In addition we axiomatise the logic of HT 2models and prove that it captures the strong equivalence of theories in partial equilibrium logic.
P.: Forgetting actions in domain descriptions
 In: Proceedings of the TwentySecond AAAI Conference on Artificial Intelligence, AAAI
, 2007
"... Forgetting irrelevant/problematic actions in a domain description can be useful in solving reasoning problems, such as query answering, planning, conflict resolution, prediction, postdiction, etc.. Motivated by such applications, we study what forgetting is, how forgetting can be done, and for whic ..."
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Cited by 2 (0 self)
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Forgetting irrelevant/problematic actions in a domain description can be useful in solving reasoning problems, such as query answering, planning, conflict resolution, prediction, postdiction, etc.. Motivated by such applications, we study what forgetting is, how forgetting can be done, and for which applications forgetting can be useful and how, in the context of reasoning about actions. We study these questions in the action language C (a formalism based on causal explanations), and relate it to forgetting in classical logic and logic programming.
Open Problems in Abstract Argumentation
"... ... argumentation. For each of the problems, we motivate why it is interesting and what makes it (apparently) hard to solve. ..."
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... argumentation. For each of the problems, we motivate why it is interesting and what makes it (apparently) hard to solve.
Die Verleihung des akademischen Grades erfolgt auf Beschluss des Rates
"... Doctor rerum naturalium ..."
Nonmonotonic Causal Logic
"... This chapter describes a nonmonotonic causal logic designed for representing knowledge about the effects of actions. A causal rule φ ⇐ ψ where φ and ψ are formulas of classical logic, is understood to express that (the truth of) ψ is a sufficient condition for φ’s being caused. A causal theory T is ..."
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This chapter describes a nonmonotonic causal logic designed for representing knowledge about the effects of actions. A causal rule φ ⇐ ψ where φ and ψ are formulas of classical logic, is understood to express that (the truth of) ψ is a sufficient condition for φ’s being caused. A causal theory T is a set of causal rules, and is assumed to describe all such sufficient conditions. Thus, given an interpretation I, the set of formulas T I = {φ  φ ⇐ ψ ∈ T and I  = ψ} can be understood to describe everything caused in a world such as I (according to T). The models of causal theory T are those interpretations for which what is true is exactly what is caused: that is, the interpretations I such that I is the unique model of T I. This fixpoint condition makes the logic nonmonotonic; adding causal rules to T may produce new models. Causal theories allow for convenient formalization of such challenging phenomena as indirect effects of actions (ramifications), implied action preconditions, concurrent interacting effects of actions, and things that change by themselves. These capabilities stem from a robust solution to the frame problem [33]: one can write causal rules
Chapter 1 Nonmonotonic Causal Logic
"... This chapter describes a nonmonotonic causal logic designed for representing knowledge about the effects of actions. A causal rule φ ⇐ ψ where φ and ψ are formulas of classical logic, is understood to express that (the truth of) ψ is a sufficient condition for φ’s being caused. A causal theory T is ..."
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This chapter describes a nonmonotonic causal logic designed for representing knowledge about the effects of actions. A causal rule φ ⇐ ψ where φ and ψ are formulas of classical logic, is understood to express that (the truth of) ψ is a sufficient condition for φ’s being caused. A causal theory T is a set of causal rules, and is assumed to describe all such sufficient conditions. Thus, given an interpretation I, the set of formulas T I = { φ  φ⇐ψ ∈ T and I  = ψ} can be understood to describe everything caused in a world such as I (according to T). The models of causal theory T are those interpretations for which what is true is exactly what is caused: that is, the interpretations I such that I is the unique model of T I. This fixpoint condition makes the logic nonmonotonic; adding causal rules to T may produce new models. Causal theories allow for convenient formalization of such challenging phenomena as indirect effects of actions (ramifications), implied action preconditions, concurrent interacting effects of actions, and things that change by themselves. These capabilities stem from a robust solution to the frame problem [33]: one can write causal rules
NINTH INTERNATIONAL CONFERENCE ON LOGIC PROGRAMMING AND NONMONOTONIC REASONING (LPNMR 2007) Workshop on Correspondence and Equivalence for Nonmonotonic Theories (CENT 2007)
, 2007
"... c ○ Copyright 2007 for the individual papers by the individual authors. Copying permitted for private and scientific purposes. Republication of material in this volume requires permission of the copyright owners. Preface This volume consists of the contributions presented at the Workshop Correspond ..."
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c ○ Copyright 2007 for the individual papers by the individual authors. Copying permitted for private and scientific purposes. Republication of material in this volume requires permission of the copyright owners. Preface This volume consists of the contributions presented at the Workshop Correspondence and Equivalence for Nonmonotonic Theories, CENT 2007, colocated with LPNMR 2007 in Tempe, Arizona, USA on May 14 2007. The systematic study of intertheory relations such as strong and uniform equivalence has recently become an active subarea of research in the field of LPNMR. Various kinds of correspondence relations that may hold between logic programs or between nonmonotonic theories have been analysed and shown to be of practical relevance for theory or program transformation, optimisation and modularity. Several systems for verifying such relations have already been implemented. The papers in this volume explore this topic further and take it in several new directions. We would like to express our warm thanks to the LPNMR programme chairs, Gerhard Brewka and John Schlipf, for agreeing to host this event in Tempe. A special thanks also to goes to Chitta Baral, the local organiser of LPNMR, for his help in accommodating the workshop and printing these proceedings. Finally, we thank the contributors for their efforts to improve our understanding of this developing area and the programme committee members for their
Interpretability and Equivalence in Quantified Equilibrium Logic
"... Abstract. The study of synonymy among propositional theories in equilibrium logic, begun in [36], is extended to the firstorder case. 1 ..."
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Abstract. The study of synonymy among propositional theories in equilibrium logic, begun in [36], is extended to the firstorder case. 1