Portail HAL des publications du LIRMM
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Abstractions of Queries in Ontology-Based Data Access
No full textInternational audienceIn ontology-based data access (OBDA), multiple data sources are integrated via mappings to an ontology. We consider an OBDA setting based on existential rules and the certain answer semantics. We address the recent issue of query abstraction, which consists of abstracting data queries by translating them to the ontology layer. Since a perfect abstraction may not exist, the notions of minimally complete and maximally sound abstractions have been introduced. We study abstractions within an extension of UCQs with a limited form of inequality and a special predicate marking database constants. While this extension does not lead to an increased complexity of the problems of interest, it is able to express minimally complete abstractions, hence perfect abstractions when they exist. We also characterize maximally sound abstractions by making a new connection with the notion of maximum recovery stemming from data exchange
Federated FAIR Semantic Artefacts Discovery and Search with OntoPortal Federation
No full textInternational audienceThe explosion in the number of ontologies and semantic artefacts has come with the importance of developing Semantic Artefact Catalogues to support diverse research communities to harvest, share and serve these artefacts as FAIR objects. However, the lack of interoperability of these catalogues hampers cross disciplinary studies and make semantic stakeholders work quite cumbersome juggling back and forth from one tool to another. In this paper, we define Semantic Artefact Catalogues interoperability and report on three approaches studied. We present the implementation of the OntoPortal Federation, i.e., the technical and collaboration processes engaged to federate multiple OntoPortal-based catalogues. We showcase how AgroPortal, EcoPortal, EarthPortal, and BiodivPortal, have been federated and now enable federated browsing and search, facilitating seamless access to distributed semantic artefacts and ontologies across their respective disciplines: agri-food, ecology, earth sciences and biodiversity. We discuss technical challenges and governance decisions and conclude by outlining future directions toward a sustainable and community-driven OntoPortal-based semantic layer for open science data infrastructures
RhizoDep: a Functional-Structural Root Model to simulate rhizodeposition
No full textRhizoDep is a functional-structural root model within the platform OpenAlea. The model has been designed to simulate rhizodeposition processes together with root growth and respiration as a function of root carbon balance within a dynamic 3D root architecture
Conformal taxonomic validation: A semi-automated validation framework for citizen science records
No full textInternational audienceCitizen science records are a valuable source of marine biodiversity data, especially where standardized sampling campaigns are limited in spatial or temporal scope. However, such records often contain biases and errors and typically require expert validation before they can reliably support scientific research. Validating large volumes of citizen science data remains an important challenge. In this paper, we present a semi-automated validation framework that combines a deep learning classifier with conformal prediction to generate sets of plausible taxonomic labels at multiple ranks, while providing rigorous control over prediction confidence. Extensive evaluation was carried out using 25,000 jellyfish records, both with and without prior validation, as well as against 800 expert-validated entries. Our results show that the method frequently produces singleton prediction sets that can be accepted automatically, offering a high-confidence and scalable solution for validating marine citizen science data
Nginx a 20 ans : gros plan sur sa sécurité
No full textNational audienceDans les articles précédents, nous avions vu les principes généraux de configuration de Nginx, et comment créer un modèle facile à instancier pour déployer des services accessibles à travers des sous-domaines. Il est temps de s’intéresser à la sécurité de votre serveur
Novel Design of Three-Channel Bilateral Teleoperation with Communication Delay Using Wave Variable Compensators
No full textInternational audienceBilateral teleoperation systems have been widely used in many fields of robotics, such as industrial manipulation, medical treatment, space exploration, and deep-sea operation. Delays in communication, known as an inevitable issues in practical implementation, especially for long-distance operations and challenging communication situations, can destroy system passivity and potentially lead to system failure. In this work, we address the time-delayed three-channel teleoperation design problem to guarantee system passivity and achieve high transparency simultaneously. To realize this, the three-channel teleoperation structure is first reformulated to form a two-channel-like architecture. Then, the wave variable technique is used to handle the communication delay and guarantee system passivity. Two novel wave variable compensators are proposed to achieve delay-minimized system transparency, and energy reservoirs are employed to monitor and regulate the energy introduced via these compensators to preserve overall system passivity. Numerical studies confirm that the proposed method significantly improves both kinematic and force tracking performance, achieving near-perfect correspondence with only a single-trip delay. Quantitative analyses using Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Dynamic Time Warping (DTW) metrics show substantial error reductions compared to conventional wave variable and direct transmission-based three-channel teleoperation approaches. Moreover, statistical validation via the Mann–Whitney U test further confirms the significance of these improvements in system performance. The proposed design guarantees passivity with any passive human operator and environment without requiring restrictive assumptions, offering a robust and generalizable solution for teleoperation tasks with communication time delay
On the Average Random Probing Model
No full textInternational audienceMasking is one of the main countermeasures against side-channel analysis since it relies on provable security. In this context, “provable” means that a security bound can be exhibited for the masked implementation through a theoretical analysis in a given threat model. The main goal in this line of research is therefore to provide the tightest security bound, in the most realistic model, in the most generic way. Yet, all of these objectives cannot be reached together. That is why the masking literature has introduced a large spectrum of threat models and reductions between them, depending on the desired trade-off with respect to these three goals. In this paper, we focus on three threat models, namely the noisy-leakage model (realistic yet hard to work with), the random probing (unrealistic yet easy to work with), and more particularly a third intermediate model called average random probing. Average random probing has been introduced by Dziembowski et al. at Eurocrypt 2015, in order to exhibit a tight reduction between noisy-leakage and random probing models, recently proven by Brian et al. at Eurocrypt 2024. This milestone has strong practical consequences, since otherwise the reduction from the noisy leakage model to the random probing model introduces a prohibitively high constant factor in the security bound, preventing security evaluators to use it in practice. However, we exhibit a gap between the average random probing definitions of Dziembowski et al. (denoted hereafter by DFS-ARP) and Brian et al. (simply denoted by ARP). Whereas any noisy leakage can be tightly reduced to DFS-ARP, we show in this paper that it cannot be tightly reduced to ARP, unless requiring extra assumptions, e.g., if the noisy leakage is deterministic. Our proof techniques do not involve more tools than the one used so far in such reductions, namely basic probability facts, and known properties of the total variation distance. As a consequence, the reduction from the noisy leakage to the random probing — without high constant factor — remains unproven. This stresses the need to clarify the practical relevance of analyzing the security of masking in the random probing model since most of the current efforts towards improving the constructions and their security proofs in the random probing model might be hindered by potentially unavoidable loss in the reduction from more realistic but currently less investigated leakage models
An autonomous surface vehicle for acoustic tracking, bathymetric and photogrammetric surveys
No full textInternational audienceAutonomous Surface Vehicles (ASVs) are becoming increasingly affordable and versatile, integrating a wide range of sensors for applications ranging from oceanographics to marine wildlife monitoring. However, the high cost and limited adaptability of commercial ASVs remain major barriers for many research applications, particularly in ecology. To address these challenges, we developed a low-cost, open-source, and reproducible ASV designed for multi-modal surveys. The ASV enables autonomous acoustic tracking of marine animals equipped with acoustic tags, achieving a mean spatial accuracy of 1 m (standard deviation of 1.8 m) over 4.5 h of continuous monitoring. Additionally, the ASV efficiently performs bathymetric surveys that meet Class 1 hydrographic survey standards, and photogrammetric surveys with a mean horizontal accuracy of 0.51 m and a vertical accuracy of 0.66 m (CE90 and LE90 metrics, respectively). The cost of the ASV varies between about US11,000, depending on sensor configurations, making is significantly more affordable than commercial alternatives. Field validations confirm the ASV’s ability to deliver high-quality, reliable data, offering an accessible and adaptable solution for ecological and environmental monitoring
Design and kinetostatic analysis of a tip-stiffness improved compliant continuum robot using anti-buckling universal joints
No full textInternational audienceCable-driven compliant continuum robots (CCRs) can reach target areas in constrained spaces due to their elastic bodies being controlled remotely. They have been widely employed to inspect, maintain, or repair industrial machines such as gas turbine engines and oil pipes. However, their performances are usually limited by the low tip stiffness and the stiffness usually decreases with the increase of cable pulling forces. This paper aims to address the above problems by presenting a tip stiffness improved CCR formed by compliant anti-buckling universal joints (ACCR). The normalized nonlinear spatial models of the one-segment CCR and three-segment CCR are proposed and comprehensively verified using commercial nonlinear finite element analysis software. Given cable forces, prescribed cable displacements, tip loads, and gravity, the motion of any points on the CCRs can be analytically obtained. The performance characteristics of the one-segment CCRs and three-segment CCRs are extensively studied under different loading conditions, including the maximum CCR deformation, tip-location accuracy, shape dexterity, and tip stiffness. The results show that the tip stiffness of the ACCR is always much higher than that of the counterpart CCR under the same loading conditions. For example, the one-segment and three-segment ACCRs both have a high in-plane tip stiffness under in-plane actuation, which can increase by 49.0% and 31.3%, respectively; and they both have a high transverse tip stiffness under spatial actuation, which can increase by 48.9% and 31.2%, respectively. It is also confirmed that the ACCRs can increase tip stiffness by increasing cable actuation. Several preliminary planar experimental tests are carried out to validate the fabrication feasibility of the prototype, the accuracy of the analytical model, and/or the above-mentioned stiffness improvement
Singularity-free trajectory tracking for steerable wheeled mobile robots
No full textOmnidirectional robots can be realized using Mecanum wheels or using a suitable arrangement of conventional steerable wheels. The latter group, known as omnidirectional steerable wheeled mobile robots (SWMRs), are known to have a lower cost with respect to the former, and to be more robust thanks to the presence of conventional wheels. Nevertheless, their modeling and control is complex, due to the presence of singularities in their representation. This paper proposes a framework for trajectory tracking of SWMRs using Nonlinear Model Predictive Control (NMPC) based on a real-time iteration scheme. The NMPC generates feasible motions for the robot, avoiding model singularities of the mobile base, together with bounds on driving and steering velocities on the wheels. Our NMPC works alongside a finite state machine, responsible for singularity avoidance during starting and stopping motion, and a state trajectory generation scheme based on dynamic feedback linearization, which makes our framework capable of tracking any trajectory. Our approach is validated on a Neobotix MPO-700 on various trajectories