Accepted Papers List

J5552
A Computational Model of Ostrom’s Institutional Analysis and Development Framework (Extended Abstract)
Nieves Montes, Nardine Osman, Carles Sierra
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Ostrom’s Institutional Analysis and Development (IAD) framework represents a comprehensive theoretical effort to identify and outline the variables that determine the outcome in any social interaction. Taking inspiration from it, we define the Action Situation Language (ASL), a machine-readable logical language to express the components of a multiagent interaction, with a special focus on the rules adopted by the community. The ASL is complemented by a game engine that takes an interaction description as input and automatically grounds its semantics as an Extensive-Form Game (EFG), which can be readily analysed using standard game-theoretical solution concepts. Overall, our model allows a community of agents to perform what-if analysis on a set of rules being considered for adoption, by automatically connecting rule configurations to the outcomes they incentivize.
List of keywords
Agent-based and Multi-agent Systems -> MAS: Normative systems
Agent-based and Multi-agent Systems -> MAS: Agent theories and models
Agent-based and Multi-agent Systems -> MAS: Agent-based simulation and emergence
Agent-based and Multi-agent Systems -> MAS: Coordination and cooperation
J5586
Data-Informed Knowledge and Strategies (Extended Abstract)
Junli Jiang, Pavel Naumov
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The article proposes a new approach to reasoning about knowledge and strategies in multiagent systems. It emphasizes data, not agents, as the source of strategic knowledge. The approach brings together Armstrong’s functional dependency expression from database theory, a data-informed knowledge modality based on a recent work by Baltag and van Benthem, and a newly proposed data-informed strategy modality. The main technical result is a sound and complete logical system that describes the interplay between these three logical operators.
List of keywords
Knowledge Representation and Reasoning -> KRR: Reasoning about actions
Knowledge Representation and Reasoning -> KRR: Reasoning about knowledge and belief
J5650
Q-Learning-Based Model Predictive Variable Impedance Control for Physical Human-Robot Collaboration (Extended Abstract)
Loris Roveda, Andrea Testa, Asad Ali Shahid, Francesco Braghin, Dario Piga
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Physical human-robot collaboration is increasingly required in many contexts. To implement an effective collaboration, the robot should be able to recognize the human’s intentions and guarantee safe and adaptive behavior along the intended motion directions. The robot-control strategies with such attributes are particularly demanded in the industrial field. Indeed, with this aim, this work proposes a Q-Learning-based Model Predictive Variable Impedance Control (Q-LMPVIC) to assist the operators in physical human-robot collaboration (pHRC) tasks. A Cartesian impedance control loop is designed to implement decoupled compliant robot dynamics. The impedance control parameters (i.e., setpoint and damping parameters) are then optimized online in order to maximize the performance of the pHRC. For this purpose, an ensemble of neural networks is designed to learn the modeling of the human-robot interaction dynamics while capturing the associated uncertainties. The derived modeling is then exploited by the model predictive controller (MPC), enhanced with stability guarantees by means of Lyapunov constraints. The MPC is solved by making use of a Q-Learning method that, in its online implementation, uses an actor-critic algorithm to approximate the exact solution. Indeed, the Q-learning method provides an accurate and highly efficient solution (in terms of computational time and resources). The proposed approach has been validated through experimental tests, in which a Franka EMIKA panda robot has been used as a test platform.
List of keywords
Robotics -> ROB: Human robot interaction
Robotics -> ROB: Applications
Robotics -> ROB: Behavior and control
Robotics -> ROB: Learning in robotics
J5685
Automatic Recognition of the General-Purpose Communicative Functions Defined by the ISO 24617-2 Standard for Dialog Act Annotation (Extended Abstract)
Eugénio Ribeiro, Ricardo Ribeiro, David Martins de Matos
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From the perspective of a dialog system, the identification of the intention behind the segments in a dialog is important, as it provides cues regarding the information present in the segments and how they should be interpreted. The ISO 24617-2 standard for dialog act annotation defines a hierarchically organized set of general-purpose communicative functions that correspond to different intentions that are relevant in the context of a dialog. In this paper, we explore the automatic recognition of these functions. To do so, we propose to adapt existing approaches to dialog act recognition, so that they can deal with the hierarchical classification problem. More specifically, we propose the use of an end-to-end hierarchical network with cascading outputs and maximum a posteriori path estimation to predict the communicative function at each level of the hierarchy, preserve the dependencies between the functions in the path, and decide at which level to stop. Additionally, we rely on transfer learning processes to address the data scarcity problem. Our experiments on the DialogBank show that this approach outperforms both flat and hierarchical approaches based on multiple classifiers and that each of its components plays an important role in the recognition of general-purpose communicative functions.
List of keywords
Natural Language Processing -> NLP: Text classification
Natural Language Processing -> NLP: Dialogue and interactive systems
J5688
Rethinking Formal Models of Partially Observable Multiagent Decision Making (Extended Abstract)
Vojtěch Kovařík, Martin Schmid, Neil Burch, Michael Bowling, Viliam Lisý
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Multiagent decision-making in partially observable environments is usually modelled as either an extensive-form game (EFG) in game theory or a partially observable stochastic game (POSG) in multiagent reinforcement learning (MARL). One issue with the current situation is that while most practical problems can be modelled in both formalisms, the relationship of the two models is unclear, which hinders the transfer of ideas between the two communities. A second issue is that while EFGs have recently seen significant algorithmic progress, their classical formalization is unsuitable for efficient presentation of the underlying ideas, such as those around decomposition. To solve the first issue, we introduce factored-observation stochastic games (FOSGs), a minor modification of the POSG formalism which distinguishes between private and public observation and thereby greatly simplifies decomposition. To remedy the second issue, we show that FOSGs and POSGs are naturally connected to EFGs: by "unrolling" a FOSG into its tree form, we obtain an EFG. Conversely, any perfect-recall timeable EFG corresponds to some underlying FOSG in this manner. Moreover, this relationship justifies several minor modifications to the classical EFG formalization that recently appeared as an implicit response to the model’s issues with decomposition. Finally, we illustrate the transfer of ideas between EFGs and MARL by presenting three key EFG techniques — counterfactual regret minimization, sequence form, and decomposition — in the FOSG framework.
List of keywords
Game Theory and Economic Paradigms -> GTEP: Noncooperative games
Agent-based and Multi-agent Systems -> MAS: Agent theories and models
Agent-based and Multi-agent Systems -> MAS: Multi-agent learning
J5758
Multi-Agent Advisor Q-Learning (Extended Abstract)
Sriram Ganapathi Subramanian, Matthew E. Taylor, Kate Larson, Mark Crowley
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In the last decade, there have been significant advances in multi-agent reinforcement learning (MARL) but there are still numerous challenges, such as high sample complexity and slow convergence to stable policies, that need to be overcome before wide-spread deployment is possible. However, many real-world environments already, in practice, deploy sub-optimal or heuristic approaches for generating policies. An interesting question that arises is how to best use such approaches as advisors to help improve reinforcement learning in multi-agent domains. We provide a principled framework for incorporating action recommendations from online sub-optimal advisors in multi-agent settings. We describe the problem of ADvising Multiple Intelligent Reinforcement Agents (ADMIRAL) in nonrestrictive general-sum stochastic game environments and present two novel Q-learning-based algorithms: ADMIRAL – Decision Making (ADMIRAL-DM) and ADMIRAL – Advisor Evaluation (ADMIRAL-AE), which allow us to improve learning by appropriately incorporating advice from an advisor (ADMIRAL-DM), and evaluate the effectiveness of an advisor (ADMIRAL-AE). We analyze the algorithms theoretically and provide fixed point guarantees regarding their learning in general-sum stochastic games. Furthermore, extensive experiments illustrate that these algorithms: can be used in a variety of environments, have performances that compare favourably to other related baselines, can scale to large state-action spaces, and are robust to poor advice from advisors.
List of keywords
Agent-based and Multi-agent Systems -> MAS: Multi-agent learning
Machine Learning -> ML: Deep reinforcement learning
Machine Learning -> ML: Reinforcement learning
J5919
Reinforcement Learning from Optimization Proxy for Ride-Hailing Vehicle Relocation (Extended Abstract)
Enpeng Yuan, Wenbo Chen, Pascal Van Hentenryck
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Idle vehicle relocation is crucial for addressing demand-supply imbalance that frequently arises in the ride-hailing system. Current mainstream methodologies – optimization and reinforcement learning – suffer from obvious computational drawbacks. Optimization models need to be solved in real-time and often trade off model fidelity (hence quality of solutions) for computational efficiency. Reinforcement learning is expensive to train and often struggles to achieve coordination among a large fleet. This paper designs a hybrid approach that leverages the strengths of the two while overcoming their drawbacks. Specifically, it trains an optimization proxy, i.e., a machine-learning model that approximates an optimization model, and refines the proxy with reinforcement learning. This Reinforcement Learning from Optimization Proxy (RLOP) approach is efficient to train and deploy, and achieves better results than RL or optimization alone. Numerical experiments on the New York City dataset show that the RLOP approach reduces both the relocation costs and computation time significantly compared to the optimization model, while pure reinforcement learning fails to converge due to computational complexity.
List of keywords
Machine Learning -> ML: Applications
Machine Learning -> ML: Reinforcement learning
Planning and Scheduling -> PS: Real-time planning
J5920
Get Out of the BAG! Silos in AI Ethics Education: Unsupervised Topic Modeling Analysis of Global AI Curricula (Extended Abstract)
Rana Tallal Javed, Osama Nasir, Melania Borit, Loïs Vanhée, Elias Zea, Shivam Gupta, Ricardo Vinuesa, Junaid Qadir
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This study explores the topics and trends of teaching AI ethics in higher education, using Latent Dirichlet Allocation as the analysis tool. The analyses included 166 courses from 105 universities around the world. Building on the uncovered patterns, we distil a model of current pedagogical practice, the BAG model (Build, Assess, and Govern), that combines cognitive levels, course content, and disciplines. The study critically assesses the implications of this teaching paradigm and challenges practitioners to reflect on their practices and move beyond stereotypes and biases.
List of keywords
AI Ethics, Trust, Fairness -> General
Data Mining -> General
Data Mining -> DM: Exploratory data mining
J5921
Mean-Semivariance Policy Optimization via Risk-Averse Reinforcement Learning (Extended Abstract)
Xiaoteng Ma, Shuai Ma, Li Xia, Qianchuan Zhao
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Keeping risk under control is often more crucial than maximizing expected rewards in real-world decision-making situations, such as finance, robotics, autonomous driving, etc. The most natural choice of risk measures is variance, while it penalizes the upside volatility as much as the downside part. Instead, the (downside) semivariance, which captures negative deviation of a random variable under its mean, is more suitable for risk-averse proposes. This paper aims at optimizing the mean-semivariance (MSV) criterion in reinforcement learning w.r.t. steady reward distribution. Since semivariance is time-inconsistent and does not satisfy the standard Bellman equation, the traditional dynamic programming methods are inapplicable to MSV problems directly. To tackle this challenge, we resort to Perturbation Analysis (PA) theory and establish the performance difference formula for MSV. We reveal that the MSV problem can be solved by iteratively solving a sequence of RL problems with a policy-dependent reward function. Further, we propose two on-policy algorithms based on the policy gradient theory and the trust region method. Finally, we conduct diverse experiments from simple bandit problems to continuous control tasks in MuJoCo, which demonstrate the effectiveness of our proposed methods.
List of keywords
Machine Learning -> ML: Reinforcement learning
Machine Learning -> ML: Deep reinforcement learning
Planning and Scheduling -> PS: Markov decisions processes
Uncertainty in AI -> UAI: Sequential decision making
J5922
Creative Problem Solving in Artificially Intelligent Agents: A Survey and Framework (Extended Abstract)
Evana Gizzi, Lakshmi Nair, Sonia Chernova, Jivko Sinapov
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Creative Problem Solving (CPS) is a sub-area within artificial intelligence that focuses on methods for solving off-nominal, or anomalous problems in autonomous systems. Despite many advancements in planning and learning in AI, resolving novel problems or adapting existing knowledge to a new context, especially in cases where the environment may change in unpredictable ways, remains a challenge. To stimulate further research in CPS, we contribute a definition and a framework of CPS, which we use to categorize existing AI methods in this field. We conclude our survey with open research questions, and suggested future directions.
List of keywords
Knowledge Representation and Reasoning -> KRR: Learning and reasoning
Humans and AI -> HAI: Cognitive systems
Multidisciplinary Topics and Applications -> MDA: Arts and creativity
Planning and Scheduling -> PS: Planning algorithms
Planning and Scheduling -> PS: Robot planning
Robotics -> ROB: Cognitive robotics
J5923
Ethical By Designer – How to Grow Ethical Designers of Artificial Intelligence (Extended Abstract)
Loïs Vanhée, Melania Borit
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Ethical concerns regarding Artificial Intelligence technology have fueled discussions around the ethics training received by its designers. Training designers for ethical behaviour, understood as habitual application of ethical principles in any situation, can make a significant difference in the practice of research, development, and application of AI systems. Building on interdisciplinary knowledge and practical experience from computer science, moral psychology, and pedagogy, we propose a functional way to provide this training.
List of keywords
Multidisciplinary Topics and Applications -> MDA: Education
AI Ethics, Trust, Fairness -> General
AI Ethics, Trust, Fairness -> ETF: AI and law, governance, regulation
AI Ethics, Trust, Fairness -> ETF: Ethical, legal and societal issues
AI Ethics, Trust, Fairness -> ETF: Moral decision making
AI Ethics, Trust, Fairness -> ETF: Societal Impact of AI
AI Ethics, Trust, Fairness -> ETF: Trustworthy AI
AI Ethics, Trust, Fairness -> ETF: Values
Humans and AI -> HAI: Computational sustainability and human wellbeing
J5924
A Logic-based Explanation Generation Framework for Classical and Hybrid Planning Problems (Extended Abstract)
Stylianos Loukas Vasileiou, William Yeoh, Son Tran, Ashwin Kumar, Michael Cashmore, Daniele Magazzeni
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In human-aware planning systems, a planning agent might need to explain its plan to a human user when that plan appears to be non-feasible or sub-optimal. A popular approach, called model reconciliation, has been proposed as a way to bring the model of the human user closer to the agent’s model. In this paper, we approach the model reconciliation problem from a different perspective, that of knowledge representation and reasoning, and demonstrate that our approach can be applied not only to classical planning problems but also hybrid systems planning problems with durative actions and events/processes.
List of keywords
Planning and Scheduling -> PS: Model-based reasoning
Humans and AI -> HAI: Human-AI collaboration
Knowledge Representation and Reasoning -> KRR: Diagnosis and abductive reasoning
Knowledge Representation and Reasoning -> KRR: Belief change
J5925
Interpretable Local Concept-based Explanation with Human Feedback to Predict All-cause Mortality (Extended Abstract)
Radwa El Shawi, Mouaz Al-Mallah
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Machine learning models are incorporated in different fields and disciplines, some of which require high accountability and transparency, for example, the healthcare sector. A widely used category of explanation techniques attempts to explain models’ predictions by quantifying the importance score of each input feature. However, summarizing such scores to provide human-interpretable explanations is challenging. Another category of explanation techniques focuses on learning a domain representation in terms of high-level human-understandable concepts and then utilizing them to explain predictions. These explanations are hampered by how concepts are constructed, which is not intrinsically interpretable. To this end, we propose Concept-based Local Explanations with Feedback (CLEF), a novel local model agnostic explanation framework for learning a set of high-level transparent concept definitions in high-dimensional tabular data that uses clinician-labeled concepts rather than raw features.
List of keywords
AI Ethics, Trust, Fairness -> ETF: Explainability and Interpretability
AI Ethics, Trust, Fairness -> ETF: Trustworthy AI
AI Ethics, Trust, Fairness -> ETF: Ethical, legal and societal issues
AI Ethics, Trust, Fairness -> General
J5926
Simplified Risk-aware Decision Making with Belief-dependent Rewards in Partially Observable Domains (Extended Abstract)
Andrey Zhitnikov, Vadim Indelman
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It is a long-standing objective to ease the computation burden incurred by the decision-making problem under partial observability. Identifying the sensitivity to simplification of various components of the original problem has tremendous ramifications. Yet, algorithms for decision-making under uncertainty usually lean on approximations or heuristics without quantifying their effect. Therefore, challenging scenarios could severely impair the performance of such methods. In this paper, we extend the decision-making mechanism to the whole by removing standard approximations and considering all previously suppressed stochastic sources of variability. On top of this extension, we scrutinize the distribution of the return. We begin from a return given a single candidate policy and continue to the pair of returns given a corresponding pair of candidate policies. Furthermore, we present novel stochastic bounds on the return and novel tools, Probabilistic Loss (PLoss) and its online accessible counterpart (PbLoss), to characterize the effect of a simplification.
List of keywords
Planning and Scheduling -> PS: POMDPs
Planning and Scheduling -> PS: Planning under uncertainty
Robotics -> ROB: Motion and path planning
Uncertainty in AI -> UAI: Sequential decision making
J5927
Adversarial Framework with Certified Robustness for Time-Series Domain via Statistical Features (Extended Abstract)
Taha Belkhouja, Janardhan Rao Doppa
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Time-series data arises in many real-world applications (e.g., mobile health) and deep neural networks (DNNs) have shown great success in solving them. Despite their success, little is known about their robustness to adversarial attacks. In this paper, we propose a novel adversarial framework referred to as Time-Series Attacks via STATistical Features (TSA-STAT). To address the unique challenges of time-series domain, TSA-STAT employs constraints on statistical features of the time-series data to construct adversarial examples. Optimized polynomial transformations are used to create attacks that are more effective (in terms of successfully fooling DNNs) than those based on additive perturbations. We also provide certified bounds on the norm of the statistical features for constructing adversarial examples. Our experiments on diverse real-world benchmark datasets show the effectiveness of TSA-STAT in fooling DNNs for time-series domain and in improving their robustness.
List of keywords
Machine Learning -> ML: Time series and data streams
Machine Learning -> ML: Robustness
J5928
SAMBA: A Generic Framework for Secure Federated Multi-Armed Bandits (Extended Abstract)
Radu Ciucanu, Pascal Lafourcade, Gael Marcadet, Marta Soare
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We tackle the problem of secure cumulative reward maximization in multi-armed bandits in a cross-silo federated learning setting. Under the orchestration of a central server, each data owner participating at the cumulative reward computation has the guarantee that its raw data is not seen by some other participant. We rely on cryptographic schemes and propose SAMBA, a generic framework for Secure federAted Multi-armed BAndits. We show that SAMBA returns the same cumulative reward as the non-secure versions of bandit algorithms, while satisfying formally proven security properties. We also show that the overhead due to cryptographic primitives is linear in the size of the input, which is confirmed by our implementation.
List of keywords
Multidisciplinary Topics and Applications -> MDA: Security and privacy
Machine Learning -> ML: Federated learning
Uncertainty in AI -> UAI: Sequential decision making
J5930
Motion Planning Under Uncertainty with Complex Agents and Environments via Hybrid Search (Extended Abstract)
Daniel Strawser, Brian Williams
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As autonomous systems tackle more real-world situations, mission success oftentimes cannot be guaranteed and the planner must reason about the probability of failure. Unfortunately, computing a trajectory that satisfies mission goals while constraining the probability of failure is difficult because of the need to reason about complex, multidimensional probability distributions. Recent methods have seen success using chance-constrained, model-based planning. We argue there are two main drawbacks to these approaches. First, current methods suffer from an inability to deal with expressive environment models such as 3D non-convex obstacles. Second, most planners rely on considerable simplifications when computing trajectory risk including approximating the agent’s dynamics, geometry, and uncertainty. We apply hybrid search to the risk-bound, goal-directed planning problem. The hybrid search consists of a region planner and a trajectory planner. The region planner makes discrete choices by reasoning about geometric regions that the agent should visit in order to accomplish its mission. In formulating the region planner, we propose landmark regions that help produce obstacle-free paths. The region planner passes paths through the environment to a trajectory planner; the task of the trajectory planner is to optimize trajectories that respect the agent’s dynamics and the user’s desired risk of mission failure. We discuss three approaches to modeling trajectory risk: a CDF-based approach, a sampling-based collocation method, and an algorithm named Shooting Method Monte Carlo. A variety of 2D and 3D test cases are presented in the full paper including a linear case, a Dubins car model, and an underwater autonomous vehicle. The method is shown to outperform other methods in terms of speed and utility of the solution. Additionally, the models of trajectory risk are shown to better approximate risk in simulation.
List of keywords
Planning and Scheduling -> PS: Planning under uncertainty
Planning and Scheduling -> PS: Robot planning
Robotics -> ROB: Motion and path planning
J5931
Core Challenges in Embodied Vision-Language Planning (Extended Abstract)
Jonathan Francis, Nariaki Kitamura, Felix Labelle, Xiaopeng Lu, Ingrid Navarro, Jean Oh
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Recent advances in the areas of Multimodal Machine Learning and Artificial Intelligence (AI) have led to the development of challenging tasks at the intersection of Computer Vision, Natural Language Processing, and Robotics. Whereas many approaches and previous survey pursuits have characterised one or two of these dimensions, there has not been a holistic analysis at the center of all three. Moreover, even when combinations of these topics are considered, more focus is placed on describing, e.g., current architectural methods, as opposed to also illustrating high-level challenges and opportunities for the field. In this survey paper, we discuss Embodied Vision-Language Planning (EVLP) tasks, a family of prominent embodied navigation and manipulation problems that jointly leverage computer vision and natural language for interaction in physical environments. We propose a taxonomy to unify these tasks and provide an in-depth analysis and comparison of the new and current algorithmic approaches, metrics, simulators, and datasets used for EVLP tasks. Finally, we present the core challenges that we believe new EVLP works should seek to address, and we advocate for task construction that enables model generalisability and furthers real-world deployment.
List of keywords
Robotics -> General
Natural Language Processing -> NLP: Applications
Planning and Scheduling -> PS: Applications
Robotics -> ROB: Learning in robotics
J5933
Constraint Solving Approaches to the Business-to-Business Meeting Scheduling Problem (Extended Abstract)
Miquel Bofill, Jordi Coll, Marc Garcia, Jesús Giráldez-Cru, Gilles Pesant, Josep Suy, Mateu Villaret
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The B2B Meeting Scheduling Optimization Problem (B2BSP) consists of scheduling a set of meetings between given pairs of participants to an event, minimizing idle time periods in participants’ schedules, while taking into account participants’ availability and accommodation capacity. Therefore, it constitutes a challenging combinatorial problem in many real-world B2B events. This work presents a comparative study of several approaches to solve this problem. They are based on Constraint Programming (CP), Mixed Integer Programming (MIP) and Maximum Satisfiability (MaxSAT). The CP approach relies on using global constraints and has been implemented in MiniZinc to be able to compare CP, Lazy Clause Generation and MIP as solving technologies in this setting. A pure MIP encoding is also presented. Finally, an alternative viewpoint is considered under MaxSAT, showing the best performance when considering some implied constraints. Experimental results on real world B2B instances, as well as on crafted ones, show that the MaxSAT approach is the one with the best performance for this problem, exhibiting better solving times, sometimes even orders of magnitude smaller than CP and MIP.
List of keywords
Constraint Satisfaction and Optimization -> CSO: Applications
Constraint Satisfaction and Optimization -> CSO: Constraint programming
Constraint Satisfaction and Optimization -> CSO: Modeling
J5934
Proofs and Certificates for Max-SAT (Extended Abstract)
Matthieu Py, Mohamed Sami Cherif, Djamal Habet
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In this paper, we present a tool, called MS-Builder, which generates certificates for the Max-SAT problem in the particular form of a sequence of equivalence-preserving transformations. To generate a certificate, MS-Builder iteratively calls a SAT oracle to get a SAT resolution refutation which is handled and adapted into a sound refutation for Max-SAT. In particular, the size of the computed Max-SAT refutation is linear with respect to the size of the initial refutation if it is semi-read-once, tree-like regular, tree-like or semi-tree-like. Additionally, we propose an extendable tool, called MS-Checker, able to verify the validity of any Max-SAT certificate using Max-SAT inference rules.
List of keywords
Constraint Satisfaction and Optimization -> CSO: Satisfiabilty
Constraint Satisfaction and Optimization -> CSO: Solvers and tools
J5935
Memory-Limited Model-Based Diagnosis (Extended Abstract)
Patrick Rodler
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Model-based diagnosis is a principled and broadly applicable AI-based approach to tackle debugging problems in a wide range of areas including software, knowledge bases, circuits, cars, and robots. Whenever the sound and complete computation of fault explanations in a given preference order (e.g., cardinality or probability) is required, all existing diagnosis algorithms suffer from an exponential space complexity. This can prevent their application on memory-restricted devices and for memory-intensive problem cases. As a remedy, we propose RBF-HS, a diagnostic search based on Korf’s seminal RBFS algorithm which can enumerate an arbitrary fixed number of fault explanations in best-first order within linear space bounds, without sacrificing other desirable properties. Evaluations on real-world diagnosis cases show that RBF-HS, when used to compute minimum-cardinality fault explanations, in most cases saves substantial space while requiring only reasonably more or even less time than Reiter’s HS-Tree, one of the most influential diagnostic algorithms with the same properties.
List of keywords
Knowledge Representation and Reasoning -> KRR: Diagnosis and abductive reasoning
Knowledge Representation and Reasoning -> KRR: Applications
Knowledge Representation and Reasoning -> KRR: Automated reasoning and theorem proving
Knowledge Representation and Reasoning -> KRR: Semantic Web
Search -> S: Applications
Search -> S: Combinatorial search and optimisation
Search -> S: Heuristic search
Uncertainty in AI -> UAI: Sequential decision making
J5936
Unsupervised and Few-Shot Parsing from Pretrained Language Models (Extended Abstract)
Zhiyuan Zeng, Deyi Xiong
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This paper proposes two Unsupervised constituent Parsing models (UPOA and UPIO) that calculate inside and outside association scores solely based on the self-attention weight matrix learned in a pretrained language model. The proposed unsupervised parsing models are further extended to few-shot parsing models (FPOA, FPIO) that use a few annotated trees to fine-tune the linear projection matrices in self-attention. Experiments on PTB and SPRML show that both unsupervised and few-shot parsing methods are better than or comparable to the previous methods.
List of keywords
Natural Language Processing -> NLP: Tagging, chunking, and parsing
Natural Language Processing -> General
J5937
Data-Driven Revision of Conditional Norms in Multi-Agent Systems (Extended Abstract)
Davide Dell’Anna, Natasha Alechina, Fabiano Dalpiaz, Mehdi Dastani, Brian Logan
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In multi-agent systems, norm enforcement is a mechanism for steering the behavior of individual agents in order to achieve desired system-level objectives. Due to the dynamics of multi-agent systems, however, it is hard to design norms that guarantee the achievement of the objectives in every operating context. Also, these objectives may change over time, thereby making previously defined norms ineffective. In this paper, we investigate the use of system execution data to automatically synthesise and revise conditional prohibitions with deadlines, a type of norms aimed at preventing agents from exhibiting certain patterns of behaviors. We propose DDNR (Data-Driven Norm Revision), a data-driven approach to norm revision that synthesises revised norms with respect to a data set of traces describing the behavior of the agents in the system. We evaluate DDNR using a state-of-the-art, off-the-shelf urban traffic simulator. The results show that DDNR synthesises revised norms that are significantly more accurate than the original norms in distinguishing adequate and inadequate behaviors for the achievement of the system-level objectives.
List of keywords
Agent-based and Multi-agent Systems -> MAS: Normative systems
Agent-based and Multi-agent Systems -> MAS: Agent-based simulation and emergence
Agent-based and Multi-agent Systems -> MAS: Coordination and cooperation
Agent-based and Multi-agent Systems -> MAS: Engineering methods, platforms, languages and tools
Agent-based and Multi-agent Systems -> MAS: Formal verification, validation and synthesis
Knowledge Representation and Reasoning -> KRR: Learning and reasoning
Machine Learning -> ML: Classification
J5938
Survey and Evaluation of Causal Discovery Methods for Time Series (Extended Abstract)
Charles K. Assaad, Emilie Devijver, Eric Gaussier
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We introduce in this survey the major concepts, models, and algorithms proposed so far to infer causal relations from observational time series, a task usually referred to as causal discovery in time series. To do so, after a description of the underlying concepts and modelling assumptions, we present different methods according to the family of approaches they belong to: Granger causality, constraint-based approaches, noise-based approaches, score-based approaches, logic-based approaches, topology-based approaches, and difference-based approaches. We then evaluate several representative methods to illustrate the behaviour of different families of approaches. This illustration is conducted on both artificial and real datasets, with different characteristics. The main conclusions one can draw from this survey is that causal discovery in times series is an active research field in which new methods (in every family of approaches) are regularly proposed, and that no family or method stands out in all situations. Indeed, they all rely on assumptions that may or may not be appropriate for a particular dataset.
List of keywords
Uncertainty in AI -> UAI: Causality, structural causal models and causal inference
Machine Learning -> ML: Time series and data streams
J5939
A Survey of Methods for Automated Algorithm Configuration (Extended Abstract)
Elias Schede, Jasmin Brandt, Alexander Tornede, Marcel Wever, Viktor Bengs, Eyke Hüllermeier, Kevin Tierney
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Algorithm configuration (AC) is concerned with the automated search of the most suitable parameter configuration of a parametrized algorithm. There are currently a wide variety of AC problem variants and methods proposed in the literature. Existing reviews do not take into account all derivatives of the AC problem, nor do they offer a complete classification scheme. To this end, we introduce taxonomies to describe the AC problem and features of configuration methods, respectively. Existing AC literature is classified and characterized by the provided taxonomies.
List of keywords
Search -> S: Algorithm portfolios and configuration
J5940
Incremental Event Calculus for Run-Time Reasoning (Extended Abstract)
Efthimis Tsilionis, Alexander Artikis, Georgios Paliouras
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We present a system for online, incremental composite event recognition. In streaming environments, the usual case is for data to arrive with a (variable) delay from, and to be revised by, the underlying sources. We propose RTEC_inc, an incremental version of RTEC, a composite event recognition engine with formal, declarative semantics, that has been shown to scale to several real-world data streams. RTEC deals with delayed arrival and revision of events by computing all queries from scratch. This is often inefficient since it results in redundant computations. Instead, RTEC_inc deals with delays and revisions in a more efficient way, by updating only the affected queries. We compare RTEC_inc and RTEC experimentally using real-world and synthetic datasets. The results are compatible with our complexity analysis and show that RTEC_inc outperforms RTEC in many practical cases.
List of keywords
Knowledge Representation and Reasoning -> General
Knowledge Representation and Reasoning -> KRR: Logic programming
Knowledge Representation and Reasoning -> KRR: Non-monotonic reasoning
Knowledge Representation and Reasoning -> KRR: Reasong about actions
Knowledge Representation and Reasoning -> KRR: Reasoning about knowledge and belief
J5941
Ordinal Maximin Share Approximation for Goods (Extended Abstract)
Hadi Hosseini, Andrew Searns, Erel Segal-Halevi
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In fair division of indivisible goods, l-out-of-d maximin share (MMS) is the value that an agent can guarantee by partitioning the goods into d bundles and choosing the l least preferred bundles. Most existing works aim to guarantee to all agents a constant fraction of their 1-out-of-n MMS. But this guarantee is sensitive to small perturbation in agents’ cardinal valuations. We consider a more robust approximation notion, which depends only on the agents’ ordinal rankings of bundles. We prove the existence of l-out-of-floor((l+1/2)n) MMS allocations of goods for any integer l greater than or equal to 1, and present a polynomial-time algorithm that finds a 1-out-of-ceiling(3n/2) MMS allocation when l = 1. We further develop an algorithm that provides a weaker ordinal approximation to MMS for any l > 1.
List of keywords
Game Theory and Economic Paradigms -> GTEP: Fair division
Game Theory and Economic Paradigms -> GTEP: Other
AI Ethics, Trust, Fairness -> ETF: Fairness and diversity
J5942
SAT Encodings for Pseudo-Boolean Constraints Together With At-Most-One Constraints (Extended Abstract)
Miquel Bofill, Jordi Coll, Peter Nightingale, Josep Suy, Felix Ulrich-Oltean, Mateu Villaret
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When solving a combinatorial problem using propositional satisfiability (SAT), the encoding of the constraints is of vital importance. Pseudo-Boolean (PB) constraints appear frequently in a wide variety of problems. When PB constraints occur together with at-most-one (AMO) constraints over the same variables, they can be combined into PB(AMO) constraints. In this paper we present new encodings for PB(AMO) constraints. Our experiments show that these encodings can be substantially smaller than those of PB constraints and allow many more instances to be solved within a time limit. We also observed that there is no single overall winner among the considered encodings, but efficiency of each encoding may depend on PB(AMO) characteristics such as the magnitude of coefficient values.
List of keywords
Constraint Satisfaction and Optimization -> CSO: Satisfiabilty
Constraint Satisfaction and Optimization -> CSO: Modeling
Constraint Satisfaction and Optimization -> CSO: Constraint satisfaction
J5943
On Tackling Explanation Redundancy in Decision Trees (Extended Abstract)
Yacine Izza, Alexey Ignatiev, Joao Marques-Silva
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Claims about the interpretability of decision trees can be traced back to the origins of machine learning (ML). Indeed, given some input consistent with a decision tree’s path, the explanation for the resulting prediction consists of the features in that path. Moreover, a growing number of works propose the use of decision trees, and of other so-called interpretable models, as a possible solution for deploying ML models in high-risk applications. This paper overviews recent theoretical and practical results which demonstrate that for most decision trees, tree paths exhibit so-called explanation redundancy, in that logically sound explanations can often be significantly more succinct than what the features in the path dictates. More importantly, such decision tree explanations can be computed in polynomial-time, and so can be produced with essentially no effort other than traversing the decision tree. The experimental results, obtained on a large range of publicly available decision trees, support the paper’s claims.
List of keywords
Machine Learning -> ML: Explainable/Interpretable machine learning
AI Ethics, Trust, Fairness -> ETF: Trustworthy AI
Constraint Satisfaction and Optimization -> CSO: Constraint satisfaction
Constraint Satisfaction and Optimization -> CSO: Satisfiabilty
Knowledge Representation and Reasoning -> KRR: Automated reasoning and theorem proving
Knowledge Representation and Reasoning -> KRR: Diagnosis and abductive reasoning
Machine Learning -> ML: Symbolic methods
J5944
A False Sense of Security (Extended Abstract)
Piero A. Bonatti
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The growing literature on confidentiality in knowledge representation and reasoning sometimes may cause a false sense of security, due to lack of details about the attacker, and some misconceptions about security-related concepts. This paper analyzes the vulnerabilities of some recent knowledge protection methods to increase the awareness about their actual effectiveness and their mutual differences.
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Multidisciplinary Topics and Applications -> MDA: Security and privacy
Knowledge Representation and Reasoning -> General
J5946
Learning to Design Fair and Private Voting Rules (Extended Abstract)
Farhad Mohsin, Ao Liu, Pin-Yu Chen, Francesca Rossi, Lirong Xia
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Voting is used widely to aggregate preferences to make a collective decision. In this paper, we focus on evaluating and designing voting rules that support both the privacy of the voting agents and a notion of fairness over such agents. First, we introduce a novel notion of group fairness and adopt the existing notion of local differential privacy. We then evaluate the level of group fairness in several existing voting rules, as well as the trade-offs between fairness and privacy, showing that it is not possible to always obtain maximal economic efficiency with high fairness. Then, we present both a machine learning and a constrained optimization approach to design new voting rules that are fair while maintaining a high level of economic efficiency. Finally, we empirically examine the effect of adding noise to create local differentially private voting rules and discuss the three-way trade-off between economic efficiency, fairness, and privacy.
List of keywords
Game Theory and Economic Paradigms -> GTEP: Computational social choice
AI Ethics, Trust, Fairness -> ETF: Fairness and diversity
Multidisciplinary Topics and Applications -> MDA: Security and privacy
J5948
Conjure: Automatic Generation of Constraint Models from Problem Specifications (Extended Abstract)
Özgür Akgün, Alan M. Frisch, Ian P. Gent, Christopher Jefferson, Ian Miguel, Peter Nightingale
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When solving a combinatorial problem, the formulation or model of the problem is critical to the efficiency of the solver. Automating the modelling process has long been of interest given the expertise and time required to develop an effective model of a particular problem. We describe a method to automatically produce constraint models from a problem specification written in the abstract constraint specification language Essence. Our approach is to incrementally refine the specification into a concrete model by applying a chosen refinement rule at each step. Any non-trivial specification may be refined in multiple ways, creating a diverse space of models to choose from. The handling of symmetries is a particularly important aspect of automated modelling. We show how modelling symmetries may be broken automatically as they enter a model during refinement, removing the need for an expensive symmetry detection step following model formulation. Our approach is implemented in a system called Conjure. We compare the models produced by Conjure to constraint models from the literature that are known to be effective. Our empirical results confirm that Conjure can reproduce successfully the kernels of the constraint models of 42 benchmark problems found in the literature.
List of keywords
Constraint Satisfaction and Optimization -> CSO: Constraint programming
Constraint Satisfaction and Optimization -> CSO: Modeling
J5949
Optimizing the Computation of Overriding in DLN (Extended Abstract)
Piero A. Bonatti, Iliana Petrova, Luigi Sauro
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One of the factors that hinder the adoption of nonmonotonic description logics in applications is performance. Even when monotonic and nonmonotonic inferences have the same asymptotic complexity, the implementation of nonmonotonic reasoning may be significantly slower. The family of nonmonotonic logics DLN is no exception to this behavior. We address this issue by introducing two provably correct and complete optimizations for reasoning in DLN. The first optimization is a module extractor that has the purpose of focusing reasoning on a relevant subset of the knowledge base. The second, called optimistic evaluation, aims at exploiting incremental reasoning in a better way. Extensive experimental evaluation shows that the optimized DLN reasoning is often compatible with interactive query answering, thus bringing nonmonotonic description logics closer to practical applications.
List of keywords
Knowledge Representation and Reasoning -> KRR: Non-monotonic reasoning
Knowledge Representation and Reasoning -> KRR: Description logics and ontologies
Knowledge Representation and Reasoning -> KRR: Semantic Web
J5950
Gradient-Based Mixed Planning with Symbolic and Numeric Action Parameters (Extended Abstract)
Kebing Jin, Hankz Hankui Zhuo, Zhanhao Xiao, Hai Wan, Subbarao Kambhampati
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Dealing with planning problems with both logical relations and numeric changes in real-world dynamic environments is challenging. Existing numeric planning systems for the problem often discretize numeric variables or impose convex constraints on numeric variables, which harms the performance when solving problems, especially when the problems contain obstacles and non-linear numeric effects. In this work, we propose a novel algorithm framework to solve numeric planning problems mixed with logical relations and numeric changes based on gradient descent. We cast the numeric planning with logical relations and numeric changes as an optimization problem. Specifically, we extend the syntax to allow parameters of action models to be either objects or real-valued numbers, which enhances the ability to model real-world numeric effects. Based on the extended modeling language, we propose a gradient-based framework to simultaneously optimize numeric parameters and compute appropriate actions to form candidate plans. The gradient-based framework is composed of an algorithmic heuristic module based on propositional operations to select actions and generate constraints for gradient descent, an algorithmic transition module to update states to the next ones, and a loss module to compute loss. We repeatedly minimize loss by updating numeric parameters and compute candidate plans until it converges into a valid plan for the planning problem.
List of keywords
Planning and Scheduling -> PS: Mixed discrete/continuous planning
Planning and Scheduling -> PS: Planning algorithms