Conflict resolution is an important issue in knowledge representation and reasoning.A common idea... more Conflict resolution is an important issue in knowledge representation and reasoning.A common idea of solving conflicts in reasoning is to add preferencesin the underlying reasoning mechanism. This paper describes extensions ofGelfond and Lifschitz's extended logic programs [5] by adding preference information.We first propose prioritized logic programs (PLPs) in which thepreference is expressed statically. An extended answer set semantics is providedfor
... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Inv... more ... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Invariants and Constraints from Action Theories}, year = {1996} }. ... We first propose a persistence-based formalism of actions, and show that the generation of action invariants is ...
... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Inv... more ... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Invariants and Constraints from Action Theories}, year = {1996} }. ... We first propose a persistence-based formalism of actions, and show that the generation of action invariants is ...
Winslett proposed a method for reasoning about action called the possible models approach (PMA). ... more Winslett proposed a method for reasoning about action called the possible models approach (PMA). The PMA successfully removed the major difficulty manifested by Ginsberg and Smith's possible worlds approach (PWA). In this paper, we show that Winslett's PMA fails to solve the frame and ramification problems for some actions, as does the PWA. From this observation, we classify actions as definite and indefinite, and find that, in general, the PMA is not appropriate for both definite and indefinite actions. We propose a new approach to formalize actions based on persistence. We compare our approach with the PMA in detail, and show that our new formalization can avoid the problems in the PMA and PWA in most cases, and give more intuitive results for reasoning about action, regardless of whether the action is definite or indefinite.
This paper is a contribution towards the body of literature which views negotiation in a qualitat... more This paper is a contribution towards the body of literature which views negotiation in a qualitative light. It builds on an existing logical framework for negotiation between rational, cooperative, truthful agents proposed in . We show that agents equipped with negotiation strategies corresponding to basic AGM belief revision operations are capable of reaching exactly the permissible deals defined and discussed in . Each agent has to present a set of weakened demands to the other party who, in return, is obliged to accept all weakened demands. The acceptance of demands is modelled by basic AGM belief revision. We extend the logical framework of (Meyer, Kwok, & Zhang 2003) by considering scenarios in which the initial demand sets of agents may vary. We show that it forces agents to limit their negotiation strategies to AGM belief revision satisfying the supplementary AGM postulates. This leads to the redefinition of a negotiation strategy as a preference relation on demands. This extended framework provides a description of the deals that an agent ought to consider as reasonable, but provides no information on how it should go about choosing a particular deal. We conclude with suggestions on how negotiation strategies can be used to do so.
. It is well known that rule-based knowledge basesare usually realized by logic programs. An upda... more . It is well known that rule-based knowledge basesare usually realized by logic programs. An update has to beperformed to the current knowledge base if some new informationoccurs. In many applications associated with dynamicdomains, however, such new information may occur not onlyas a set of simple facts but also a set of rules. In this paper,we view knowledge bases as
ACM Transactions on Programming Languages and Systems, 1989
In this paper we propose a denotational semantics for Prolog and an approach to the abstract inte... more In this paper we propose a denotational semantics for Prolog and an approach to the abstract interpretation of Prolog programs; we deal with the control rules of Prolog and the cut operator. Moreover, we get a simple denotation for negation as nite failure. The abstract analysis is proposed both for computed answers analysis and for call patterns analysis. In both cases the abstract semantics is nitely computable. Two examples show the usefulness of our approach for the analysis of Prolog programs.
We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is ... more We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is forgotten from a logic program, all atoms in the set should be eliminated from this program in some way, and other atoms related to them in the program might also be affected. We define notions of strong and weak forgettings in logic programs to capture such intuition, reveal their close connections to the notion of forgetting in classical propositional theories, and provide a precise semantic characterization for them. Based on these notions, we then develop a general framework for conflict solving in logic programs. We investigate various semantic properties and features in relation to strong and weak forgettings and conflict solving in the proposed framework. We argue that many important conflict solving problems can be represented within this framework. In particular, we show that all major logic program update approaches can be transformed into our framework, under which each approach becomes a specific conflict solving case with certain constraints. We also study essential computational properties of strong and weak forgettings and conflict solving in the framework.
We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is ... more We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is forgotten from a logic program, all atoms in the set should be eliminated from this program in some way, and other atoms related to them in the program might also be affected. We define notions of strong and weak forgettings in logic programs to capture such intuition, reveal their close connections to the notion of forgetting in classical propositional theories, and provide a precise semantic characterization for them. Based on these notions, we then develop a general framework for conflict solving in logic programs. We investigate various semantic properties and features in relation to strong and weak forgettings and conflict solving in the proposed framework. We argue that many important conflict solving problems can be represented within this framework. In particular, we show that all major logic program update approaches can be transformed into our framework, under which each approach becomes a specific conflict solving case with certain constraints. We also study essential computational properties of strong and weak forgettings and conflict solving in the framework.
Possible-world semantics are provided for Parikh's relevance-sensitive model for belief revision.... more Possible-world semantics are provided for Parikh's relevance-sensitive model for belief revision. Having Grove's system-of-spheres construction as a base, we consider additional constraints on measuring distance between possible worlds, and we prove that, in the presence of the AGM postulates, these constraints characterize precisely Parikh's axiom (P). These additional constraints essentially generalize a criterion of similarity that predates axiom (P) and was originally introduced in the context of Reasoning about Action. A by-product of our study is the identification of two possible readings of Parikh's axiom (P), which we call the strong and the weak versions of the axiom. An interesting feature of the strong version is that, unlike classical AGM belief revision, it makes associations between the revision policies of different theories.
1 Introduction Causality plays a basic role in human reasoning. The philo-sophical study of causa... more 1 Introduction Causality plays a basic role in human reasoning. The philo-sophical study of causality dates back to the origin of the dis-cipline. AI research in causality finds its impetus in consider-ations from commonsense reasoning, especially the ramifica-tion problem. It ...
... For instance, causal laws can express any" causal law" in the sense of McCain andTu... more ... For instance, causal laws can express any" causal law" in the sense of McCain andTurner ([McCain and Turner 1995]). ... Therefore McCain and Turner's solution to the ramification problem can be re-coded in the extended dynamic logic. ...
This paper presents a logical framework for negotiation based on belief revision theory. We consi... more This paper presents a logical framework for negotiation based on belief revision theory. We consider that a negotiation process is a course or multiple courses of mutual belief revision. A set of AGM-style postulates are proposed to capture the rationality of competitive and cooperative behaviors of negotiation. We first show that the AGM revision and its iterated extension is a special case of negotiation function. Then we show that a negotiation function can be constructed by two related iterated belief revision functions under a certain coordination mechanism. This provides a qualitative method for constructing negotiation space and rational concessions. It also shows a glimpse of how to express game-theoretical concepts in logical framework.
This paper provides a logical framework for negotiation between agents that are assumed to be rat... more This paper provides a logical framework for negotiation between agents that are assumed to be rational, cooperative and truthful. We present a characterisation of the permissible outcomes of a process of negotiation in terms of a set of rationality postulates, as well as a method for constructing exactly the rational outcomes. The framework is extended by describing two modes of negotiation from which an outcome can be reached. In the concessionary mode, agents are required to weaken their demands in order to accommodate the demands of others. In the adaptationist mode, agents are required to adapt to the demands of others in some appropriate fashion. Both concession and adaptation are characterised in terms of rationality postulates. We also provide methods for constructing exactly the rational concessions, as well as the rational adaptations. The central result of the paper is the observation that the outcomes obtained from the concessionary and adaptationist modes both correspond to the rational outcomes. We conclude by pointing out the links between negotiation and AGM belief change, and providing a glimpse of how this may be used to define a notion of preference-based negotiation.
Negotiation between two agents is modelled as a one-time encounter between two extended logic pro... more Negotiation between two agents is modelled as a one-time encounter between two extended logic programs. Each offers an answer set. Their mu- tual deal can be regarded as a trade on their an- swer sets. An agent can achieve this by weaken- ing its program to surrender some literals that con- flict with the offer of the other agent. We
Conflict resolution is an important issue in knowledge representation and reasoning.A common idea... more Conflict resolution is an important issue in knowledge representation and reasoning.A common idea of solving conflicts in reasoning is to add preferencesin the underlying reasoning mechanism. This paper describes extensions ofGelfond and Lifschitz's extended logic programs [5] by adding preference information.We first propose prioritized logic programs (PLPs) in which thepreference is expressed statically. An extended answer set semantics is providedfor
... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Inv... more ... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Invariants and Constraints from Action Theories}, year = {1996} }. ... We first propose a persistence-based formalism of actions, and show that the generation of action invariants is ...
... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Inv... more ... MISC{Zhang96derivinginvariants, author = {Yan Zhang and Norman Y. Foo}, title = {Deriving Invariants and Constraints from Action Theories}, year = {1996} }. ... We first propose a persistence-based formalism of actions, and show that the generation of action invariants is ...
Winslett proposed a method for reasoning about action called the possible models approach (PMA). ... more Winslett proposed a method for reasoning about action called the possible models approach (PMA). The PMA successfully removed the major difficulty manifested by Ginsberg and Smith's possible worlds approach (PWA). In this paper, we show that Winslett's PMA fails to solve the frame and ramification problems for some actions, as does the PWA. From this observation, we classify actions as definite and indefinite, and find that, in general, the PMA is not appropriate for both definite and indefinite actions. We propose a new approach to formalize actions based on persistence. We compare our approach with the PMA in detail, and show that our new formalization can avoid the problems in the PMA and PWA in most cases, and give more intuitive results for reasoning about action, regardless of whether the action is definite or indefinite.
This paper is a contribution towards the body of literature which views negotiation in a qualitat... more This paper is a contribution towards the body of literature which views negotiation in a qualitative light. It builds on an existing logical framework for negotiation between rational, cooperative, truthful agents proposed in . We show that agents equipped with negotiation strategies corresponding to basic AGM belief revision operations are capable of reaching exactly the permissible deals defined and discussed in . Each agent has to present a set of weakened demands to the other party who, in return, is obliged to accept all weakened demands. The acceptance of demands is modelled by basic AGM belief revision. We extend the logical framework of (Meyer, Kwok, & Zhang 2003) by considering scenarios in which the initial demand sets of agents may vary. We show that it forces agents to limit their negotiation strategies to AGM belief revision satisfying the supplementary AGM postulates. This leads to the redefinition of a negotiation strategy as a preference relation on demands. This extended framework provides a description of the deals that an agent ought to consider as reasonable, but provides no information on how it should go about choosing a particular deal. We conclude with suggestions on how negotiation strategies can be used to do so.
. It is well known that rule-based knowledge basesare usually realized by logic programs. An upda... more . It is well known that rule-based knowledge basesare usually realized by logic programs. An update has to beperformed to the current knowledge base if some new informationoccurs. In many applications associated with dynamicdomains, however, such new information may occur not onlyas a set of simple facts but also a set of rules. In this paper,we view knowledge bases as
ACM Transactions on Programming Languages and Systems, 1989
In this paper we propose a denotational semantics for Prolog and an approach to the abstract inte... more In this paper we propose a denotational semantics for Prolog and an approach to the abstract interpretation of Prolog programs; we deal with the control rules of Prolog and the cut operator. Moreover, we get a simple denotation for negation as nite failure. The abstract analysis is proposed both for computed answers analysis and for call patterns analysis. In both cases the abstract semantics is nitely computable. Two examples show the usefulness of our approach for the analysis of Prolog programs.
We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is ... more We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is forgotten from a logic program, all atoms in the set should be eliminated from this program in some way, and other atoms related to them in the program might also be affected. We define notions of strong and weak forgettings in logic programs to capture such intuition, reveal their close connections to the notion of forgetting in classical propositional theories, and provide a precise semantic characterization for them. Based on these notions, we then develop a general framework for conflict solving in logic programs. We investigate various semantic properties and features in relation to strong and weak forgettings and conflict solving in the proposed framework. We argue that many important conflict solving problems can be represented within this framework. In particular, we show that all major logic program update approaches can be transformed into our framework, under which each approach becomes a specific conflict solving case with certain constraints. We also study essential computational properties of strong and weak forgettings and conflict solving in the framework.
We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is ... more We consider how to forget a set of atoms in a logic program. Intuitively, when a set of atoms is forgotten from a logic program, all atoms in the set should be eliminated from this program in some way, and other atoms related to them in the program might also be affected. We define notions of strong and weak forgettings in logic programs to capture such intuition, reveal their close connections to the notion of forgetting in classical propositional theories, and provide a precise semantic characterization for them. Based on these notions, we then develop a general framework for conflict solving in logic programs. We investigate various semantic properties and features in relation to strong and weak forgettings and conflict solving in the proposed framework. We argue that many important conflict solving problems can be represented within this framework. In particular, we show that all major logic program update approaches can be transformed into our framework, under which each approach becomes a specific conflict solving case with certain constraints. We also study essential computational properties of strong and weak forgettings and conflict solving in the framework.
Possible-world semantics are provided for Parikh's relevance-sensitive model for belief revision.... more Possible-world semantics are provided for Parikh's relevance-sensitive model for belief revision. Having Grove's system-of-spheres construction as a base, we consider additional constraints on measuring distance between possible worlds, and we prove that, in the presence of the AGM postulates, these constraints characterize precisely Parikh's axiom (P). These additional constraints essentially generalize a criterion of similarity that predates axiom (P) and was originally introduced in the context of Reasoning about Action. A by-product of our study is the identification of two possible readings of Parikh's axiom (P), which we call the strong and the weak versions of the axiom. An interesting feature of the strong version is that, unlike classical AGM belief revision, it makes associations between the revision policies of different theories.
1 Introduction Causality plays a basic role in human reasoning. The philo-sophical study of causa... more 1 Introduction Causality plays a basic role in human reasoning. The philo-sophical study of causality dates back to the origin of the dis-cipline. AI research in causality finds its impetus in consider-ations from commonsense reasoning, especially the ramifica-tion problem. It ...
... For instance, causal laws can express any" causal law" in the sense of McCain andTu... more ... For instance, causal laws can express any" causal law" in the sense of McCain andTurner ([McCain and Turner 1995]). ... Therefore McCain and Turner's solution to the ramification problem can be re-coded in the extended dynamic logic. ...
This paper presents a logical framework for negotiation based on belief revision theory. We consi... more This paper presents a logical framework for negotiation based on belief revision theory. We consider that a negotiation process is a course or multiple courses of mutual belief revision. A set of AGM-style postulates are proposed to capture the rationality of competitive and cooperative behaviors of negotiation. We first show that the AGM revision and its iterated extension is a special case of negotiation function. Then we show that a negotiation function can be constructed by two related iterated belief revision functions under a certain coordination mechanism. This provides a qualitative method for constructing negotiation space and rational concessions. It also shows a glimpse of how to express game-theoretical concepts in logical framework.
This paper provides a logical framework for negotiation between agents that are assumed to be rat... more This paper provides a logical framework for negotiation between agents that are assumed to be rational, cooperative and truthful. We present a characterisation of the permissible outcomes of a process of negotiation in terms of a set of rationality postulates, as well as a method for constructing exactly the rational outcomes. The framework is extended by describing two modes of negotiation from which an outcome can be reached. In the concessionary mode, agents are required to weaken their demands in order to accommodate the demands of others. In the adaptationist mode, agents are required to adapt to the demands of others in some appropriate fashion. Both concession and adaptation are characterised in terms of rationality postulates. We also provide methods for constructing exactly the rational concessions, as well as the rational adaptations. The central result of the paper is the observation that the outcomes obtained from the concessionary and adaptationist modes both correspond to the rational outcomes. We conclude by pointing out the links between negotiation and AGM belief change, and providing a glimpse of how this may be used to define a notion of preference-based negotiation.
Negotiation between two agents is modelled as a one-time encounter between two extended logic pro... more Negotiation between two agents is modelled as a one-time encounter between two extended logic programs. Each offers an answer set. Their mu- tual deal can be regarded as a trade on their an- swer sets. An agent can achieve this by weaken- ing its program to surrender some literals that con- flict with the offer of the other agent. We
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