Technology
Symbolic Model Checking for One-Resource RB+-ATL
Alechina, Natasha (University of Nottingham) | Logan, Brian (University of Nottingham) | Nguyen, Hoang Nga (University of Nottingham) | Raimondi, Franco (Middlesex University)
RB+-ATL is an extension of ATL where it is possible to model consumption and production of several resources by a set of agents. The model-checking problem for RB+-ATL is known to be decidable. However the only available model-checking algorithm for RB+-ATL uses a forward search of the state space, and hence does not have an efficient symbolic implementation. In this paper, we consider a fragment of RB+-ATL, 1RB+-ATL, that allows only one resource type. We give a symbolic model-checking algorithm for this fragment of RB+-ATL, and evaluate the performance of an MCMAS-based implementation of the algorithm on an example problem that can be scaled to large state spaces.
Formal Analysis of Dialogues on Infinite Argumentation Frameworks
Belardinelli, Francesco (Universitรฉ d'Evry) | Grossi, Davide (University of Liverpool) | Maudet, Nicolas (Sorbonne Universitรฉs, UPMC University of Paris 06, CNRS, UMR 7606, LIP6)
The paper analyses multi-agent strategic dialogues on possibly infinite argumentation frameworks. We develop a formal model for representing such dialogues, and introduce FO A -ATL, a first-order extension of alternating-time logic, for expressing the interplay of strategic and argumentation-theoretic properties. This setting is investigated with respect to the model checking problem, by means of a suitable notion of bisimulation. This notion of bisimulation is also used to shed light on how static properties of argumentation frameworks influence their dynamic behaviour.
From Raw Sensor Data to Detailed Spatial Knowledge
Zhang, Peng (Australian National University) | Lee, Jae Hee (Australian National University) | Renz, Jochen (Australian National University)
Qualitative spatial reasoning deals with relational spatial knowledge and with how this knowledge can be processed efficiently. Identifying suitable representations for spatial knowledge and checking whether the given knowledge is consistent has been the main research focus in the past two decades. However, where the spatial information comes from, what kind of information can be obtained and how it can be obtained has been largely ignored. This paper is an attempt to start filling this gap. We present a method for extracting detailed spatial information from sensor measurements of regions. We analyse how different sparse sensor measurements can be integrated and what spatial information can be extracted from sensor measurements. Different from previous approaches to qualitative spatial reasoning, our method allows us to obtain detailed information about the internal structure of regions. The result has practical implications, for example, in disaster management scenarios, which include identifying the safe zones in bushfire and flood regions.
An Ontology Matching Approach Based on Affinity-Preserving Random Walks
Xiang, Chuncheng (Peking University) | Chang, Baobao (Peking University) | Sui, Zhifang (Peking University)
Ontology matching is the process of finding semantic correspondences between entities from different ontologies. As an effective solution to linking different heterogeneous ontologies, ontology matching has attracted considerable attentions in recent years. In this paper, we propose a novel graph-based approach to ontology matching problem. Different from previous work, we formulate ontology matching as a random walk process on the association graph constructed from the to-be-matched ontologies. In particular, two variants of the conventional random walk process, namely, Affinity-Preserving Random Walk (APRW) and Mapping-Oriented Random Walk (MORW), have been proposed to alleviate the adverse effect of the false-mapping nodes in the association graph and to incorporate the 1-to-1 matching constraints presumed in ontology matching, respectively. Experiments on the Ontology Alignment Evaluation Initiative (OAEI) datasets show that our approach achieves a competitive performance when compared with state-of-the-art systems, even though our approach does not utilize any external resources.
Heroic versus Collaborative AI for the Arts
d' (Goldsmiths, University of London) | Inverno, Mark (Monash Univesity) | McCormack, Jon
This paper considers the kinds of AI systems we want involved in art and art practice. We explore this relationship from three perspectives: as artists interested in expanding and developing our own creative practice; as AI researchers interested in building new AI systems that contribute to the understanding and development of art and art practice; and as audience members interested in experiencing art. We examine the nature of both art practice and experiencing art to ask how AI can contribute. To do so, we review the history of work in intelligent agents which broadly speaking sits in two camps: autonomous agents (systems that can exhibit intelligent behaviour independently) in one, and multi-agent systems (systems which interact with other systems in communities of agents) in the other. In this context we consider the nature of the relationship between AI and Art and introduce two opposing concepts: that of โHeroic AIโ, to describe the situation where the software takes on the role of the lone creative hero and โCollaborative AIโ where the system supports, challenges and provokes the creative activity of humans. We then set out what we believe are the main challenges for AI research in understanding its potential relationship to art and art practice.
On the Consistency of AUC Pairwise Optimization
Gao, Wei (Nanjing University) | Zhou, Zhi-Hua (Nanjing University)
AUC (Area Under ROC Curve) has been an important critrion widely used in diversity learning tasks. To optimize AUC, many learning approaches have been developed, most working with pairwise surrogate losses. Thus, it is important to study the AUC consistency based on minimizing pairwise surrogate losses. In this paper, we introduce the generalized calibration for AUC optimization, and prove that it is a necessary condition for AUC consistency. We then provide a new sufficient condition for AUC consistency, and show its usefulness in studying the consistency of various surrogate losses, as well as the invetion of new consistent losses. Further, we derive regret bounds for exponential and logistic losses, and present regret bounds for more general surrogate losses in realizable setting. Finally, we prove regret bounds that disclose the equivalence between the pairwise exponential loss of AUC and the univariate exponential loss of accuracy.
The Power of Local Manipulation Strategies in Assignment Mechanisms
Mennle, Timo (University of Zurich) | Weiss, Michael (University of Zurich) | Philipp, Basil (University of Zurich) | Seuken, Sven (University of Zurich)
We consider three important, non-strategyproof assignment mechanisms: Probabilistic Serial and two variants of the Boston mechanism. Under each of these mechanisms, we study the agentโs manipulation problem of determining a best response, i.e., a report that maximizes the agentโs expected utility. In particular, we consider local manipulation strategies, which are simple heuristics based on local, greedy search. We make three main contributions. First, we present results from a behavioral experiment (conducted on Amazon Mechanical Turk) which demonstrate that human manipulation strategies can largely be explained by local manipulation strategies. Second, we prove that local manipulation strategies may fail to solve the manipulation problem optimally. Third, we show via large-scale simulations that despite this non-optimality, these strategies are very effective on average. Our results demonstrate that while the manipulation problem may be hard in general, even cognitively or computationally bounded (human) agents can find near-optimal solutions almost all the time via simple local search strategies.
Realizability of Three-Valued Semantics for Abstract Dialectical Frameworks
Pรผhrer, Jรถrg (Leipzig University)
We investigate fundamental properties of three-valued semantics for abstract dialectical frameworks (ADFs). In particular, we deal with realizability, i.e., the question whether there exists an ADF that has a given set of interpretations as its semantics. We provide necessary and sufficient conditions that hold for a set of three-valued interpretations whenever there is an ADF realizing it under admissible, complete, grounded, or preferred semantics. Moreover, we discuss how to construct such an ADF in case of realizability. Our results lay the ground for studying the expressiveness of ADFs under three-valued semantics. As a first application we study implications of our results on the existence of certain join operators on ADFs.
Count-Based Frequency Estimation with Bounded Memory
Bellemare, Marc G. (Google DeepMind)
Count-based estimators are a fundamental building block of a number of powerful sequential prediction algorithms, including Context Tree Weighting and Prediction by Partial Matching. Keeping exact counts, however, typically results in a high memory overhead. In particular, when dealing with large alphabets the memory requirements of count-based estimators often become prohibitive. In this paper we propose three novel ideas for approximating count-based estimators using bounded memory. Our first contribution, of independent interest, is an extension of reservoir sampling for sampling distinct symbols from a stream of unknown length, which we call K-distinct reservoir sampling. We combine this sampling scheme with a state-of-the-art count-based estimator for memoryless sources, the Sparse Adaptive Dirichlet (SAD) estimator. The resulting algorithm, the Budget SAD, naturally guarantees a limit on its memory usage. We finally demonstrate the broader use of K-distinct reservoir sampling in nonparametric estimation by using it to restrict the branching factor of the Context Tree Weighting algorithm. We demonstrate the usefulness of our algorithms with empirical results on two sequential, large-alphabet prediction problems.
Collective Biobjective Optimization Algorithm for Parallel Test Paper Generation
Nguyen, Minh Luan (Institute for Infocomm Research) | Hui, Siu Cheung (Nanyang Technological University) | Fong, Alvis C. M. (University of Glasgow)
Parallel Test Paper Generation ( k -TPG) is a biobjective distributed resource allocation problem, which aims to generate multiple similarly optimal test papers automatically according to multiple user-specified criteria.Generating high-quality parallel test papers is challenging due to its NP-hardness in maximizing the collective objective functions.In this paper, we propose a Collective Biobjective Optimization (CBO) algorithm for solving k -TPG. CBO is a multi-step greedy-based approximation algorithm, which exploits the submodular property for biobjective optimization of k -TPG.Experiment results have shown that CBO has drastically outperformed the current techniques in terms of paper quality and runtime efficiency.