Natasha Alechina

University of Nottingham, Nottigham, England, United Kingdom

Are you Natasha Alechina?

Claim your profile

Publications (109)14.93 Total impact

  • Thomas Ågotnes · Natasha Alechina
    [Show abstract] [Hide abstract]
    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. We also study logics with interaction axioms connecting coalitional ability and knowledge.
    No preview · Article · Jan 2016 · Journal of Logic and Computation
  • Source
    H. Du · N. Alechina · G. Hart · M. Jackson
    [Show abstract] [Hide abstract]
    ABSTRACT: A software tool MatchMaps was designed to facilitate matching between geospatial features held in different datasets, especially an authoritative dataset and a crowd-sourced dataset. MatchMaps is not fully automatic; it requires human interaction to resolve problematic matching cases. Previous studies have shown that this approach results in higher precision and recall than those achieved by fully automatic tools. In this study, we aim to evaluate MatchMaps with respect to the amount of human effort required for matching, and compare it with a fully manual matching process.
    Full-text · Article · Jul 2015
  • Natasha Alechina · Nils Bulling · Brian Logan · Hoang Nga Nguyen
    [Show abstract] [Hide abstract]
    ABSTRACT: The model-checking problem for Resource Agent Logic is known to be undecidable. We review existing (un)decidability results and identify a significant fragment of the logic for which model checking is decidable. We discuss aspects which makes model checking decidable and prove undecidability of two open fragments over a class of models in which agents always have a choice of doing nothing.
    No preview · Conference Paper · Jul 2015
  • Source
    Hoang Nga Nguyen · Natasha Alechina · Brian Logan · Abdur Rakib
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jun 2015 · Journal of Logic and Computation
  • Source
    N. Alechina · F. Liu · B. Logan
    [Show abstract] [Hide abstract]
    ABSTRACT: In this article, we study a minimal change approach to preference dynamics. We treat a set of preferences as a special kind of theory, and define minimal change preference contraction and revision operations in the spirit of the Alchourrón, Gärdenfors, and Makinson 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 then define minimal contraction by a set of preferences, and show that the problem of a minimal contraction by a set of preferences is NP-hard.
    Full-text · Article · May 2015 · Journal of Logic and Computation
  • Natasha Alechina · Nils Bulling · Mehdi Dastani · Brian Logan
    [Show abstract] [Hide abstract]
    ABSTRACT: Norms have been widely proposed as a means of coordinating and controlling the behaviour of agents in a multi-agent system. A key challenge in normative MAS is norm enforcement: how and when to restrict the agents' behaviour in order to obtain a desirable outcome? Even if a norm can be enforced theoretically, it may not be enforceable in a grounded, practical setting. In this paper we study the problem of practical norm enforcement. The key notion is that of a guard. Guards are functions which restrict the possible actions after a history of events. We propose a formal, computational model of norms, guards and norm enforcement, based on linear-time temporal logic with past operators. We show that not all norms can be enforced by such guard functions, even in the presence of unlimited computational power to reason about future events. We analyse which norms can be enforced by guards if only a fixed lookahead is available. We investigate decision problems for this question with respect to specific classes of norms, related to safety and liveness properties. Copyright © 2015, International Foundation for Autonomous Agents and Multiagent Systems.
    No preview · Conference Paper · May 2015
  • Source
    Natasha Alechina · Brian Logan · Hoang Nga Nguyen · Franco Raimondi
    [Show abstract] [Hide abstract]
    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.
    Preview · Article · Apr 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We describe a tool, MatchMaps, that generates sameAs and partOf matches between spatial objects (such as shops, shopping centres, etc.) in crowd-sourced and authoritative geospatial datasets. MatchMaps uses reasoning in qualitative spatial logic, description logic and truth maintenance techniques, to produce a consistent set of matches. We report the results of an initial eval- uation of MatchMaps by experts from Ordnance Survey (Great Britain’s National Mapping Authority). In both the case studies considered, MatchMaps was able to correctly match spatial objects (high precision and recall) with minimal human intervention.
    Full-text · Conference Paper · Jan 2015
  • N. Alechina · B. Logan · H.N. Nguyen · F. Raimondi · L. Mostarda
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we present a symbolic implementation of a model checking algorithm for the verification of properties expressed in Resource-Bounded Alternating Time Temporal Logic (RB-ATL). The implementation is based on the model checker MCMAS. We evaluate the performance of our implementation using simple multi- agent model checking problems of increasing complexity. Copyright © 2015, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.
    No preview · Article · Jan 2015
  • Source
    Abba Lawan · Abdur Rakib · Natasha Alechina · Asha Karunaratne
    [Show abstract] [Hide abstract]
    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.
    Full-text · Conference Paper · Nov 2014
  • Natasha Alechina · Brian Logan · Hoang Nga Nguyen · Franco Raimondi
    [Show abstract] [Hide abstract]
    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 consumption of resources is decidable.
    No preview · Article · Aug 2014 · Frontiers in Artificial Intelligence and Applications
  • Source
    Thomas Ågotnes · Natasha Alechina
    [Show abstract] [Hide abstract]
    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 ...
    Preview · Article · Jun 2014 · Journal of Logic Language and Information
  • Thomas Ågotnes · Natasha Alechina
    [Show abstract] [Hide abstract]
    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.
    No preview · Article · Jun 2014 · Journal of Logic Language and Information
  • Natasha Alechina · Mehdi Dastani · Brian Logan
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we consider the runtime monitoring of norms with imperfect monitors. A monitor is imperfect for a norm if it has insufficient observational capabilities to determine if a given execution trace of a multi-agent system complies with or violates the norm. One approach to the problem of imperfect monitors is to enhance the observational capabilities of the normative organisation. However this may be costly or in some cases impossible. Instead we show how to synthesise an approximation of an 'ideal' norm that can be perfectly monitored given a monitor, and which is optimal in the sense that any other approximation would fail to detect at least as many violations of the ideal norm. We give a logical analysis of (im)perfect monitors. We state the computational complexity of the norm approximation problem, and give an optimal algorithm for generating optimal approximations of norms given a monitor. Copyright © 2014, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.
    No preview · Article · May 2014
  • J.H. Lee · J. Padget · B. Logan · D. Dybalova · N. Alechina
    [Show abstract] [Hide abstract]
    ABSTRACT: Normative systems offer a means to govern agent behaviour in dynamic open environments. Under the governance, individual agents themselves must reason about compliance with state-or event-based norms (or both) depending upon the formalism used. This paper describes how norm awareness enables a BDI agent to exhibit norm compliant behaviour at run-time taking into account normative factors. To this end, we propose N-Jason, a run-time norm compliant BDI agent framework which supports norm-aware deliberation as well as a run-time norm execution mechanism, through which previously unknown norms are recognized and bring about the triggering of plans. To be able to process a norm such as an obligation, the agent architecture must be able to deal with deadlines and priorities, and choose between plans triggered by a particular norm. Consequently, we extend the syntax and the scheduling algorithm of AgentSpeak(RT) to operate in the context of Jason/Agent Speak(1) and provide 'real-time agency'. Copyright © 2014, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.
    No preview · Article · Jan 2014
  • Source
    H. Du · N. Alechina
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose a new qualitative spatial logic for reasoning about part-whole relations between geometries (sets of points) represented in different geospatial datasets, in particular crowd-sourced datasets. Since geometries in crowd-sourced data can be less inaccurate or precise, we buffer geometries by a margin of error or level of tolerance σ, and define part-whole relation for buffered geometries. The relations between geometries considered in the logic are: buffered part of (BPT), Near and Far. We provide a sound and complete axiomatisation of the logic with respect to metric models, and show that its satisfiability problem is NP-complete.
    Full-text · Article · Jan 2014 · Frontiers in Artificial Intelligence and Applications
  • Thu Trang Doan · Y. Yao · Natasha Alechina · Brian Logan
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a new approach to verifying heterogeneous multi-agent programs - multi-agent systems in which the agents are implemented in different (BDI-based) agent programming languages. Our approach is based on meta-APL, a BDI-based agent programming language that allows both an agent's plans and its deliberation strategy to be encoded as part of the agent program. The agent programs comprising a heterogeneous multi-agent program are first translated into meta-APL, and the resulting system is then verified using the Maude term rewriting system. We prove correctness of translations of Jason and 3APL programs and deliberation strategies into meta-APL. Preliminary experimental results indicate that our approach can significantly out-perform previous approaches to verification of heterogeneous multi-agent programs. Copyright © 2014, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.
    No preview · Article · Jan 2014
  • Natasha Alechina
    [Show abstract] [Hide abstract]
    ABSTRACT: Agent programming languages based on the belief, desire and intentions (BDI) framework present some interesting challenges for logicians. While BDI logics have been studied extensively, problems related to belief update and analysis of plans in BDI agent programming languages have received less attention.
    No preview · Article · Aug 2013
  • Natasha Alechina · Mehdi Dastani · Brian Logan
    [Show abstract] [Hide abstract]
    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.
    No preview · Conference Paper · Aug 2013
  • Source
    [Show abstract] [Hide abstract]
    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.
    Full-text · Conference Paper · Jul 2013

Publication Stats

708 Citations
14.93 Total Impact Points

Institutions

  • 2000-2015
    • University of Nottingham
      • School of Computer Science
      Nottigham, England, United Kingdom
  • 2014
    • University of Bergen
      • Department of Information Science and Media Studies
      Bergen, Hordaland, Norway
  • 2006
    • University of Birmingham
      • School of Computer Science
      Birmingham, ENG, United Kingdom
    • University Pompeu Fabra
      Barcino, Catalonia, Spain
  • 1994-2002
    • University of Amsterdam
      • Department of Computer Science
      Amsterdamo, North Holland, Netherlands