Natasha Alechina

University of Bergen, Bergen, Hordaland, Norway

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Publications (94)9.66 Total impact

  • Proceedings of the 24th International Joint Conference on Artificial Intelligence (IJCAI 2015); 07/2015
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    ABSTRACT: Many problems in AI and multi-agent systems research are most naturally formulated in terms of the abilities of a coalition of agents. There exist several excellent logical tools for reasoning about coalitional ability. However, coalitional ability can be affected by the availability of resources, and there is no straightforward way of reasoning about resource requirements in logics such as Coalition Logic (CL) and Alternating-time Temporal Logic (ATL). In this article, we describe a logic for reasoning about coalitional ability under resource constraints. We extend ATL with costs of actions and hence of strategies. We give a complete and sound axiomatization of the resulting logic, Resource-Bounded ATL (RB-ATL) and a model-checking algorithm for it.
    Journal of Logic and Computation 06/2015; DOI:10.1093/logcom/exv034 · 0.50 Impact Factor
  • Natasha Alechina, Nils Bulling, Mehdi Dastani, Brian Logan
    Proceedings of the 14th International Conference on Autonomous Agents and Multi-Agent Systems (AAMAS 2015); 05/2015
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    ABSTRACT: Several logics for expressing coalitional ability under resource bounds have been proposed and studied in the literature. Previous work has shown that if only consumption of resources is considered or the total amount of resources produced or consumed on any path in the system is bounded, then the model-checking problem for several standard logics, such as Resource-Bounded Coalition Logic (RB-CL) and Resource-Bounded Alternating-Time Temporal Logic (RB-ATL) is decidable. However, for coalition logics with unbounded resource production and consumption, only some undecidability results are known. In this paper, we show that the model-checking problem for RB-ATL with unbounded production and con- sumption of resources is decidable but EXPSPACE-hard. We also investigate some tractable cases and provide a detailed comparison to a variant of the resource logic RAL, together with new complexity results.
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    ABSTRACT: Due to their powerful knowledge representation formalism and associated inference mechanisms, ontology-based approaches have been increasingly adopted to formally represent domain knowledge. We propose the use of ontologies to advance knowledge-sharing on underutilized crops and propose how to integrate those ontologies with rules for added expressiveness. We first present a survey on using ontologies in the field of life-sciences with emphasis on crop-related ontologies, and justify why we need a new formalism. We then present the UC-ONTO (an Underutilized Crops Ontology) as a case study showing the integration of OWL (Web Ontology Language) ontologies with Semantic Web Rule Language (SWRL) rules.
    CEUR Workshop Proceedings of The Second International Workshop on Linked Data and Ontology in Practice, Chiang Mai, Thailand; 11/2014
  • Thomas Ågotnes, Natasha Alechina
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    ABSTRACT: This special issue on Formal Models of Awareness contains five papers that concentrate on different approaches to the notion of awareness. They include syntactic and semantic approaches to modelling awareness (awareness of formulas as opposed to awareness of semantic objects such as sets of possoble worlds) and an alternative view from the multi-agent systems perspective where awareness is identified as the ability to perceive and understand actions of other agents.Velázquez-Quesada studies a logic of plausibility acknowledgement models used to interpret the notions of implicit and explicit beliefs. The models use the notion of a formula being acknowledged as true that is similar to syntactic awareness in that the set of formulas acknowledged as true by an agent is not assumed to be closed under logical consequence. However it has a different meaning (of not just being aware of the formula, but being aware that the formula is is true). A dynamic epistemic logic over such models is cons ...
    Journal of Logic Language and Information 06/2014; 23(2):105-106. DOI:10.1007/s10849-014-9202-3
  • Thomas Ågotnes, Natasha Alechina
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    ABSTRACT: In the most popular logics combining knowledge and awareness, it is not possible to express statements about knowledge of unawareness such as “Ann knows that Bill is aware of something Ann is not aware of”—without using a stronger statement such as “Ann knows that Bill is aware of \(p\) and Ann is not aware of \(p\) ”, for some particular \(p\) . In Halpern and Rêgo (Proceedings of KR 2006; Games Econ Behav 67(2):503–525, 2009b) Halpern and Rêgo introduced a logic in which such statements about knowledge of unawareness can be expressed. The logic extends the traditional framework with quantification over formulae, and is thus very expressive. As a consequence, it is not decidable. In this paper we introduce a decidable logic which can be used to reason about certain types of unawareness. Our logic extends the traditional framework with an operator expressing full awareness, i.e., the fact that an agent is aware of everything, and another operator expressing relative awareness, the fact that one agent is aware of everything another agent is aware of. The logic is less expressive than Halpern’s and Rêgo’s logic. It is, however, expressive enough to express all of the motivating examples in Halpern and Rêgo (Proceedings of KR 2006; Games Econ Behav 67(2):503–525, 2009b). In addition to proving that the logic is decidable and that its satisfiability problem is PSPACE-complete, we present an axiomatisation which we show is sound and complete.
    Journal of Logic Language and Information 06/2014; 23(2):197-217. DOI:10.1007/s10849-014-9201-4
  • Natasha Alechina, Mehdi Dastani, Brian Logan
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    ABSTRACT: We consider the problem of updating a multi-agent system with a set of conditional norms. A norm comes into effect when its condition becomes true, and imposes either an obligation or a prohibition on an agent which remains in force until a state satisfying a deadline condition is reached. If the norm is violated, a sanction is imposed on the agent. We define a notion of a normative update of a multi-agent system by a set of conditional norms, and study the problem of checking whether the agent(s) can bring about a state satisfying a property without incurring a specified number of sanctions.
    Proceedings of the Twenty-Third international joint conference on Artificial Intelligence; 08/2013
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    ABSTRACT: In many logic-based BDI agent programming languages, plan selection involves inferencing over some underlying knowledge representation. While context-sensitive plan selection facilitates the development of flexible, declarative programs, the overhead of evaluating repeated queries to the agent’s beliefs and goals can result in poor run time performance. In this paper we present an approach to multi-cycle query caching for logic-based BDI agent programming languages. We extend the abstract performance model presented in (Alechina et al. 2012) to quantify the costs and benefits of caching query results over multiple deliberation cycles. We also present results of experiments with prototype implementations of both single- and multi-cycle caching in three logic-based BDI agent platforms, which demonstrate that significant performance improvements are achievable in practice.
    Twenty-Seventh AAAI Conference on Artificial Intelligence (AAAI-13); 07/2013
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    Heshan Du, Natasha Alechina, Mike Jackson, Glen Hart
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    ABSTRACT: The rapid development of crowd-sourcing or volunteered geographic information both challenges and provides opportunities to authoritative geospatial information. Matching geospatial ontologies is an essential element to realizing the synergistic use of disparate geospatial information. We propose a new semiautomatic method to match formal and informal real life geospatial ontologies, at both terminology level and instance level, ensuring that overall information is logically coherent and consistent. Disparate geospatial ontologies are matched by finding a consistent and coherent set of mapping axioms with respect to them. Disjointness axioms are generated in order to facilitate detection of errors. In contrast to other existing methods, disjointness axioms are seen as assumptions, which can be retracted during the overall process. We produce candidates for retraction automatically, but the ultimate decision is taken by domain experts. Geometry matching, lexical matching and cardinality checking are combined when matching geospatial individuals (spatial features).
    16th AGILE Conference on Geographic Information Science; 01/2013
  • Conference Paper: Minimal Preference Change
    Natasha Alechina, Fenrong Liu, Brian Logan
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    ABSTRACT: We propose a novel approach to preference change. We treat a set of preferences as a special kind of theory, and define minimal change contraction and revision operations in the spirit of minimal change as advocated by the Alchourron, Gardenfors, and Makinson (AGM) theory of belief revision. We characterise minimal contraction of preference sets by a set of postulates and prove a representation theorem. We also give a linear time algorithm which implements minimal contraction by a single preference. We also define minimal contraction by a set of preferences, and for a significant special case state postulates, prove a representation theorem, and provide an efficient algorithm implementing minimal contraction by a set of preferences.
    Proceedings of the Fourth International Workshop on Logic, Rationality and Interaction,, Hangzhou; 01/2013
  • Natasha Alechina, Philippe Balbiani, Dmitry Shkatov
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    ABSTRACT: We consider multi-modal logic (with countably infinite number of basic modalities) extended with additional modalities and corresponding to the union and intersection of all basic modalities. We present complete and sound axiomatic systems and polynomial-space terminating tableau-based decision procedures for the basic logic in this language, and its deterministic counterpart . We also show that admits filtration, which can be used independently of our tableaux to establish its decidability.
    Journal of Applied Non-Classical Logics 12/2012; 22(4):275-294. DOI:10.1080/11663081.2012.705960
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    Conference Paper: The logic of NEAR and FAR
    Heshan Du, Natasha Alechina, Kristin Stock, Mike Jackson
    COSIT 2013: Conference on Spatial Information Theory, Scarborough, UK; 09/2012
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    ABSTRACT: This article describes results from a research project undertaken to explore the technical issues associated with integrating unstructured crowd sourced data with authoritative national mapping data. The ultimate objective is to develop methodologies to ensure the feature enrichment of authoritative data, using crowd sourced data. Users increasingly find that they wish to use data from both kinds of geographic data sources. Different techniques and methodologies can be developed to solve this problem. In our previous research, a position map matching algorithm was developed for integrating authoritative and crowd sourced road vector data, and showed promising results (Anand et al. 2010). However, especially when integrating different forms of data at the feature level, these techniques are often time consuming and are more computationally intensive than other techniques available. To tackle these problems, this project aims at developing a methodology for automated conflict resolution, linking and merging of geographical information from disparate authoritative and crowd-sourced data sources. This article describes research undertaken by the authors on the design, implementation, and evaluation of algorithms and procedures for producing a coherent ontology from disparate geospatial data sources. To integrate road vector data from disparate sources, the method presented in this article first converts input data sets to ontologies, and then merges these ontologies into a new ontology. This new ontology is then checked and modified to ensure that it is consistent. The developed methodology can deal with topological and geometry inconsistency and provide more flexibility for geospatial information merging.
    Transactions in GIS 08/2012; 16(4):no–no. DOI:10.1111/j.1467-9671.2012.01303.x · 0.54 Impact Factor
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    Thomas Ågotnes, Natasha Alechina
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    ABSTRACT: Coalition logic is currently one of the most popular logics for multi-agent systems. While logics combining coalitional and epistemic operators have received considerable attention, completeness results for epistemic extensions of coalition logic have so far been missing. In this paper we provide several such results and proofs. We prove completeness for epistemic coalition logic with common knowledge, with distributed knowledge, and with both common and distributed knowledge, respectively. Furthermore, we completely characterise the complexity of the satisfiability problem for each of the three logics.
    Proceedings of the 11th International Conference on Autonomous Agents and Multiagent Systems - Volume 2; 06/2012
  • Natasha Alechina, Mehdi Dastani, Brian Logan
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    ABSTRACT: Normative organisations provide a means to coordinate the activities of individual agents in multiagent settings. The coordination is realized at run time by creating obligations and prohibitions (norms) for individual agents. If an agent cannot meet an obligation or violates a prohibition, the organisation imposes a sanction on the agent. In this paper, we consider norm-aware agents that deliberate on their goals, norms and sanctions before deciding which plan to select and execute. A norm-aware agent is able to violate norms (accepting the resulting sanctions) if it is in the agent's overall interests to do so, e.g., if meeting an obligation would result in an important goal of the agent becoming unachievable. Programming norm-aware agents in conventional BDI-based agent programming languages is difficult, as they lack support for deliberating about goals, norms, sanctions and deadlines. We present the norm-aware agent programming language N-2APL. N-2APL is based on 2APL and provides support for beliefs, goals, plans, norms, sanctions and deadlines. We give the syntax and semantics of N-2APL, and show that N-2APL agents are rational in the sense of committing to a set of plans that will achieve the agent's most important goals and obligations by their deadlines while respecting its most important prohibitions.
    Proceedings of the 11th International Conference on Autonomous Agents and Multiagent Systems - Volume 2; 06/2012
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    Conference Paper: Consensus games
    Julian Zappala, Natasha Alechina, Brian Logan
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    ABSTRACT: Consensus Games (CGs) are a novel approach to modelling coalition formation in multi-agent systems inspired by threshold models in sociology. In a CG, each agent's degree of commitment to the coalitions in which it may participate is expressed as a quorum function. Agents are willing to form a coalition only if a quorum consensus can be achieved amongst all agents of the coalition.
    Proceedings of the 11th International Conference on Autonomous Agents and Multiagent Systems - Volume 3; 06/2012
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    N. Alechina
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    ABSTRACT: This talk is on reasoning about agent programs written in Belief, Desire and Intention (BDI) agent programming languages. BDI programming languages (for example, [1], [2], [3]) have high-level programming primitives which correspond to the beliefs, goals and plans of an AI agent. A program contains a set of rules which allow the agent to adopt plans given its current beliefs and goals. Plans are essentially imperative programs. For example, an agent may have a rule which says that if it believes that it is currently located in room 1 and its goal is to be in room 2, then a suitable plan to adopt would be to exit room 1, turn right, move forward for 3 meters, turn right, and enter room 2.
    Temporal Representation and Reasoning (TIME), 2012 19th International Symposium on; 01/2012
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    ABSTRACT: Facilities for handling plan execution failures are essential for agents which must cope with the effects of nondeterministic actions, and some form of failure handling can be found in most mature agent programming languages and platforms. While such features simplify the development of more robust agents, they make it hard to reason about the execution of agent programs, e.g., to verify their correctness. In this paper, we present an approach to the verification of agent programs which admit exceptional executions. We consider executions of the BDI-based agent programming language 3APL in which plans containing non-executable actions can be revised using plan revision rules, and present a logic for reasoning about normal and exceptional executions of 3APL programs. We provide a complete axiomatization for the logic and, using a simple example, show how to express properties of 3APL programs as formulas of the logic.
    Theoretical Computer Science 10/2011; 412:6115-6134. DOI:10.1016/j.tcs.2011.05.052 · 0.52 Impact Factor
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    Thomas Ågotnes, Natasha Alechina
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    ABSTRACT: Coalition logic is one of the most popular logics for multi-agent systems. While epistemic extensions of coalition logic have received much attention, existence of their complete axiomatisations has so far been an open problem. In this paper we settle several of those problems. We prove completeness for epistemic coalition logic with common knowledge, with distributed knowledge, and with both common and distributed knowledge, respectively.

Publication Stats

596 Citations
9.66 Total Impact Points

Institutions

  • 2007–2014
    • University of Bergen
      • Department of Information Science and Media Studies
      Bergen, Hordaland, Norway
  • 2000–2014
    • University of Nottingham
      • School of Computer Science
      Nottigham, England, United Kingdom
  • 2006
    • University of Birmingham
      • School of Computer Science
      Birmingham, ENG, United Kingdom
    • University Pompeu Fabra
      Barcino, Catalonia, Spain
  • 1994–1998
    • University of Amsterdam
      • Department of Computer Science
      Amsterdamo, North Holland, Netherlands