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Abductive Logic Programming Agents with Destructive Databases
"... Abstract. In this paper we present an agent language that combines agent functionality with an action theory and model-theoretic semantics. The language is based on abductive logic programming (ALP), but employs a simplified state-free syntax, with an operational semantics that uses destructive upda ..."
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Cited by 24 (8 self)
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Abstract. In this paper we present an agent language that combines agent functionality with an action theory and model-theoretic semantics. The language is based on abductive logic programming (ALP), but employs a simplified state-free syntax, with an operational semantics that uses destructive updates to manipulate a database, which represents the current state of the environment. The language builds upon the ALP combination of logic programs, to represent an agent’s beliefs, and integrity constraints, to represent the agent’s goals. Logic programs are used to define macro-actions, intensional predicates, and plans to reduce goals to sub-goals including actions. Integrity constraints are used to represent reactive rules, which are triggered by the current state of the database and recent agent actions and external events. The execution of actions and the assimilation of observations generate a sequence of database states. In the case of the successful solution of all goals, this sequence, taken as a whole, determines a model that makes the agent’s goals and beliefs all true.
Towards practical tabled abduction usable in decision making
- Accepted in 5th Intl. Conf. on Intelligent Decision Technologies. Available at http://centria.di.fct.unl.pt/˜lmp/publications/ online-papers/tabdual_decision_making.pdf
, 2013
"... Abstract. Abduction as reasoning paradigm has been much explored in Artificial Intelligence, but not yet taken up by decision making as much as its potential warrants. Indeed, abduction permits the generation of hypothetical knowledge based scenarios, about which one can then equate decisions. One r ..."
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Cited by 9 (9 self)
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Abstract. Abduction as reasoning paradigm has been much explored in Artificial Intelligence, but not yet taken up by decision making as much as its potential warrants. Indeed, abduction permits the generation of hypothetical knowledge based scenarios, about which one can then equate decisions. One reason for this state of affairs is that abduction is difficult to implement efficaciously, even by experts, which entails that abductive systems are not readily available for decision making. Our concept of tabled abduction mitigates this, in the abductive logic programming system TABDUAL. The contribution of this paper is three-fold: (1) We discuss some TABDUAL improvements towards its more practical use, particularly in decision making, (2) We show that declarative debugging can be viewed as abduction in logic programming, thus showing another potential of abduction for decision making, and (3) We describe how TABDUAL can be applied in decision making and examine its benefit.
Abductive Logic Programming with Tabled Abduction
"... Abstract—In abductive logic programming, abductive solutions are typically computed without attending to the abductive context. These abductive solutions can actually be reused in a different abductive context. In this paper, we employ a tabling mechanism and propose a tabled abduction mechanism, th ..."
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Abstract—In abductive logic programming, abductive solutions are typically computed without attending to the abductive context. These abductive solutions can actually be reused in a different abductive context. In this paper, we employ a tabling mechanism and propose a tabled abduction mechanism, that consists of a transformation from abductive normal logic programs into tabled dual programs, by tabling abductive solution entries and without requiring any meta-interpreter. Recomputation of abductive solutions for a different context, but consistent with them, can then be avoided, by reusing the tabled abductive solution entries. Though our implementation is in XSB-Prolog, its concepts may be imported to other systems, not necessarily Logic Programming ones. Keywords-tabled abduction; abduction transformation; wellfounded semantics; XSB-Prolog. I.
Towards Practical Tabled Abduction in Logic Programs
"... Abstract. Despite its potential as a reasoning paradigm in AI applications, abduction has been on the back burner in logic programming, as abduction can be too difficult to implement, and costly to perform, in particular if abductive solutions are not tabled. If they become tabled, then abductive so ..."
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Cited by 7 (5 self)
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Abstract. Despite its potential as a reasoning paradigm in AI applications, abduction has been on the back burner in logic programming, as abduction can be too difficult to implement, and costly to perform, in particular if abductive solutions are not tabled. If they become tabled, then abductive solutions can be reused, even from one abductive context to another. On the other hand, current Prolog systems, with their tabling mechanisms, are mature enough to facilitate the introduction of tabling abductive solutions (tabled abduction) into them. The concept of tabled abduction has been realized recently in an abductive logic programming system TABDUAL. Besides tabling abductive solutions, TABDUAL also relies on the dual transformation. In this paper, we emphasize two TABDUAL improvements: (1) the dual transformation by need, and (2) a new construct for accessing ongoing abductive solutions, that permits modular mixes between abductive and non-abductive program parts. We apply subsequently these improvements on two distinct problems, and evaluate the performance and the scalability of TABDUAL on several benchmarks on the basis of these problems, by examining four TABDUAL variants.
A Logic-Based Framework for Reactive Systems
"... Abstract. We sketch a logic-based framework in which computation consists of performing actions to generate a sequence of states, with the purpose of making a set of reactive rules in the logical form antecedents � consequents all true. The antecedents of the rules are conjunctions of past or presen ..."
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Cited by 6 (3 self)
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Abstract. We sketch a logic-based framework in which computation consists of performing actions to generate a sequence of states, with the purpose of making a set of reactive rules in the logical form antecedents � consequents all true. The antecedents of the rules are conjunctions of past or present conditions and events, and the consequents of the rules are disjunctions of conjunctions of future conditions and actions. The antecedents can be viewed as complex/composite events, and the consequents as complex/composite/macro actions or processes. States are represented by sets of atomic sentences, and can be viewed as global variables, relational databases, Herbrand models, or mental representations of the real world. Events, including actions, transform one state into another. The operational semantics maintains only a single, destructively updated current state, whereas the model-theoretic semantics treats the entire sequence of states, events and actions as a single model. The model-theoretic semantics can be viewed as the problem of generating a model that makes all the reactive rules true.
Towards modeling morality computationally with logic programming
- In PADL 2014, volume 8324 of LNCS
"... Abstract. We investigate the potential of logic programming (LP) to model moral-ity aspects studied in philosophy and psychology. We do so by identifying three morality aspects that appear in our view amenable to computational modeling by appropriately exploiting LP features: dual-process model (rea ..."
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Cited by 6 (4 self)
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Abstract. We investigate the potential of logic programming (LP) to model moral-ity aspects studied in philosophy and psychology. We do so by identifying three morality aspects that appear in our view amenable to computational modeling by appropriately exploiting LP features: dual-process model (reactive and de-liberative) in moral judgments; justification of moral judgments by contractual-ism; and intention in moral permissibility. The research aims at developing an LP-based system with features needed in modeling moral settings, putting em-phasis on modeling these above mentioned morality aspects. We have currently co-developed two essential ingredients of the LP system, i.e., abduction and logic program updates, by exploiting the benefits of tabling features in logic programs. They serve as the basis for our whole system, into which other reasoning facets will be integrated, to model the surmised morality aspects. Moreover, we touch upon the potential of our ongoing studies of LP based cognitive features for the emergence of computational morality, in populations of agents enabled with the capacity for intention recognition, commitment and apology.
F.: Towards a logic-based unifying framework for computing. Available at http://www.doc.ic.ac.uk/˜rak/papers/TUF.pdf
, 2013
"... Computer Science today lacks a unified view of Computing. Instead, the main subareas, most notably artificial intelligence, database systems and programming languages, offer different and often competing approaches to knowledge representation, problem-solving and computation. In this paper we propos ..."
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Cited by 5 (0 self)
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Computer Science today lacks a unified view of Computing. Instead, the main subareas, most notably artificial intelligence, database systems and programming languages, offer different and often competing approaches to knowledge representation, problem-solving and computation. In this paper we propose a unifying logic-based, framework for Computing, inspired by artificial intelligence, but scaled down for practical database and programming applications. Computation in the framework is viewed as the task of generating a sequence of state transitions, with the purpose of making an agent’s goals all true. States are represented by sets of atomic sentences (or facts), representing the values of program variables, tuples in a coordination language, facts in relational databases, or Herbrand models. In the model-theoretic semantics, the entire sequence of states and events are combined into a single model-theoretic structure, by associating time stamps with facts. But in the operational semantics, facts are updated destructively, without time stamps. We show that the model generated by destructive updates is identical to the model generated by reasoning with facts containing time stamps. We also extend the model with intentional predicates and composite event predicates defined by logic programs containing conditions in first-order logic (FOL). We extend the notions of local stratification and weak stratification to generate the associated model.
Counterfactuals in Logic Programming with Applications to Morality
"... Counterfactuals are conjectures about alternatives to events that did not occur in the past; thoughts about what would have happened, had an alternative event oc-curred. Herein we show how counterfactual reasoning is modeled using Logic Programming (LP), particularly by benefitting from LP abduction ..."
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Cited by 5 (5 self)
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Counterfactuals are conjectures about alternatives to events that did not occur in the past; thoughts about what would have happened, had an alternative event oc-curred. Herein we show how counterfactual reasoning is modeled using Logic Programming (LP), particularly by benefitting from LP abduction and updating. The ap-proach is inspired by Pearl’s causal model of counter-factuals, where causal direction and conditional reason-ing are captured by inferential arrows of rules in logic programs. In this approach, LP abduction hypothesizes background conditions from given evidences or obser-vations, whereas LP updating helps frame these back-ground conditions as a counterfactual’s context. More-over, LP updating imposes causal interventions into the program, imposing minimal adjustments in the model through defeasible LP rules. We apply counterfactuals to computational morality resorting to this LP-based approach, and show their potential for specifying and querying morality issues, viz., to examine viewpoints on moral permissibility of actions through classic moral examples from literature. The results from this applica-tion have been validated on a prototype implementing the approach on top of an integrated LP abduction and updating system with tabling.
Implementing tabled abduction in logic programs.” Submitted to Doctoral Symposium on Artificial Intelligence (SDIA), Available at http://centria.di.fct.unl. pt/~lmp/publications/online-papers/implementing_tabdual.pdf
, 2013
"... Abstract. Abduction has been on the back burner in logic programming, as abduction can be too difficult to implement, and costly to perform, in particular if abductive solutions are not tabled. If they become tabled, then abductive solutions can be reused, even from one abductive context to another. ..."
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Cited by 4 (4 self)
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Abstract. Abduction has been on the back burner in logic programming, as abduction can be too difficult to implement, and costly to perform, in particular if abductive solutions are not tabled. If they become tabled, then abductive solutions can be reused, even from one abductive context to another. On the other hand, current Prolog systems, with their tabling mechanisms, are mature enough to facilitate the introduction of tabling abductive solutions (tabled abduction) into them. We recently proposed and published a conception of tabled abduction with its prototype, TABDUAL, implemented in XSB-Prolog. We detail here subsequent progress that has been made on the implementation aspect of TABDUAL, towards its more practical use.
Teleo-Reactive Abductive Logic Programs
"... Abstract. Teleo-reactive (TR) programs are a variety of production systems with a destructively updated database that represents the current state of the environment. They combine proactive behaviour, which is goal-oriented, with reactive behaviour, which is sensitive to the changing environment. Th ..."
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Cited by 4 (2 self)
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Abstract. Teleo-reactive (TR) programs are a variety of production systems with a destructively updated database that represents the current state of the environment. They combine proactive behaviour, which is goal-oriented, with reactive behaviour, which is sensitive to the changing environment. They can take advantage of situations in which the environment opportunistically solves the system’s goals, recover gracefully when the environment destroys solutions of its goals, and abort durative actions when higher priority goals need more urgent attention. In this paper, we present an abductive logic programming (ALP) representation of TR programs, following the example of our ALP representation of the logic-based production system language LPS. The operational semantics of the representation employs a destructively updated database, which represents the current state of the environment, and avoids the frame problem of explicitly reasoning about the persistence of facts that are not affected by the updates. The model-theoretic semantics of the representation is defined by associating a logic program with the TR program, the sequence of observations and actions, and the succession of database states. In the semantics, the task is to generate actions so that all of the program’s goals are true in a minimal model of this associated logic program.
