Decision support system for blockchain (DLT) platform selection based on ITU recommendations: A systematic literature review approach

Blockchain technologies, also known as Distributed Ledger Technologies (DLT), are increasingly being explored in many applications, especially in the presence of (potential) dis-/mis-/un-trust among organizations and individuals. Today, there exists a plethora of DLT platforms on the market, which makes it challenging for system designers to decide what platform they should adopt and implement. Although a few DLT comparison frameworks have been proposed in the literature, they often fail in covering all performance and functional aspects, adding that they too rarely build upon standardized criteria and recommendations. Given this state of affairs, the present paper considers a recent and exhaustive set of assessment criteria recommended by the ITU (International Telecommunication Union). Those criteria (about fifty) are nonetheless mostly defined in a textual form, which may pose interpretation problems during the implementation process. To avoid this, a systematic literature review regarding each ITU criterion is conducted with a twofold objective: (i) to understand to what extent a given criterion is considered/evaluated by the literature; (ii) to come up with ‘formal’ metric definition (i.e., on a mathematical or experimental ground) based, whenever possible, on the current literature. Following this formalization stage, a decision support tool called CREDO-DLT, which stands for “multiCRiteria-basEd ranking Of Distributed Ledger Technology platforms”, is developed using AHP and TOPSIS, which is publicly made available to help decision-maker to select the most suitable DLT platform alternative (i.e., that best suits their needs and requirements). A use case scenario in the context of energy communities is proposed to show the practicality of CREDO-DLT. •Blockchain (DLT) standardization initiatives are reviewed.•To what extent ITU’s DLT assessment criteria are covered in literature is studied.•A mathematical formalizations of the ITU recommendations are proposed.•A decision support tool (CREDO-DLT) is designed for DLT platform selection.•An energy community use case is developed to show the practicality of CREDO-DLT

Promoting the use of the PRECISE score for prostate MRI during active surveillance: results from the ESOR Nicholas Gourtsoyiannis teaching fellowship

OBJECTIVES: The PRECISE criteria for serial multiparametric magnetic resonance imaging (MRI) of the prostate during active surveillance recommend the use of a dedicated scoring system (PRECISE score) to assess the likelihood of clinically significant radiological change. This pilot study assesses the effect of an interactive teaching course on prostate MRI during active surveillance in assessing radiological change in serial imaging. METHODS: Eleven radiology fellows and registrars with different experience in prostate MRI reading participated in a dedicated teaching course where they initially evaluated radiological change (based on their previous training in prostate MRI reading) independently in fifteen patients on active surveillance (baseline and follow-up scan), and then attended a lecture on the PRECISE score. The initial scans were reviewed for teaching purposes and afterwards the participants re-assessed the degree of radiological change in a new set of images (from fifteen different patients) applying the PRECISE score. Receiver operating characteristic analysis was performed. Confirmatory biopsies and PRECISE scores given in consensus by two radiologists (involved in the original draft of the PRECISE score) were the reference standard. RESULTS: There was a significant improvement in the average area under the curve (AUC) for the assessment of radiological change from baseline (AUC: 0.60 [Confidence Intervals: 0.51-0.69] to post-teaching (AUC: 0.77 [0.70-0.84]). This was an improvement of 0.17 [0.016-0.28] (p = 0.004). CONCLUSIONS: A dedicated teaching course on the use of the PRECISE score improves the accuracy in the assessment of radiological change in serial MRI of the prostate

Choroidal Blood Flow Regulation after Posture Change or Isometric Exercise in Men with Obstructive Sleep Apnea Syndrome

PURPOSE. Obstructive sleep apnea (OSA) syndrome generates hypertension, atherosclerosis, and endothelial and autonomic dysfunction, which may mutually interact with ocular vascular regulation. Exercise and posture changes can be used to manipulate blood pressure, ocular perfusion pressure (OPP), or both. It was hypothesized that choroidal vascular reactivity in response to isometric exercise and posture changes could be altered in OSA patients. METHODS. Healthy men were matched 1:1 for body mass index, sex, and age with patients with newly diagnosed OSA without cardiovascular comorbidities. All subjects underwent sleep studies and cardiovascular phenotyping (24-hour blood pressure monitoring, arterial stiffness measurements, and cardiac and carotid echography). Choroidal reactivity was assessed by laser Doppler flowmetry, which measured subfoveal choroidal blood flow. RESULTS. During exercise, blood pressure parameters increased significantly within the same range, with a similar profile over time in OSA patients and control subjects. A significant linear relationship (P ϭ 0.0003) was noted between choroidal vascular resistance and the OPP changes during exercise in OSA patients and control subjects. From the sitting to the supine position, a significant decrease in mean arterial pressure occurred in both groups (10.9%-13.4%; P Ͻ 0.001). In both populations, no significant change in choroidal blood flow or vascular resistance was found during the posture change. Choroidal blood flow responses to exercise and posture changes were unchanged after 6 to 9 months of continuous positive airway pressure treatment. CONCLUSIONS. This study strongly suggests that the regulation of choroidal blood flow, which depends on the orthosympathetic and parasympathetic systems, is unaltered in men with OSA who have no comorbidities. (ClinicalTrials.gov number, NCT00874913.) (Invest Ophthalmol Vis Sci. 2011; 52:9489 -9496

Cometary Origin of the Zodiacal Cloud and Carbonaceous Micrometeorites

The zodiacal cloud is a thick circumsolar disk of small debris particles produced by asteroid collisions and comets. Here, we present a zodiacal cloud model based on the orbital properties and lifetimes of comets and asteroids, and on the dynamical evolution of dust after ejection. The model is quantitatively constrained by IRAS observations of thermal emission, but also qualitatively consistent with other zodiacal cloud observations. We find that 85-95% of the observed mid-infrared emission is produced by particles from the Jupiter-family comets (JFCs) and $<$10% by dust from long period comets. Asteroidal dust is found to be present at $<$10%. We suggest that spontaneous disruptions of JFCs, rather than the usual cometary activity driven by sublimating volatiles, is the main mechanism that librates cometary particles into the zodiacal cloud. Our results imply that JFC particles represent $\sim$85% of the total mass influx at Earth. Since their atmospheric entry speeds are typically low ($\approx$14.5 km s$^{-1}$ mean for D=100-200 $\mu$m with $\approx$12 km s$^{-1}$ being the most common case), many JFC grains should survive frictional heating and land on the Earth's surface. This explains why most micrometeorites collected in antarctic ice have primitive carbonaceous composition. The present mass of the inner zodiacal cloud at $<$5 AU is estimated to be 1-$2\times10^{19}$ g, mainly in D=100-200 $\mu$m particles. The inner zodiacal cloud should have been $>10^4$ times brighter during the Late Heavy Bombardment (LHB) epoch $\approx$3.8 Gyr ago, when the outer planets scattered numerous comets into the inner solar system. The bright debris disks with a large 24-$\mu$m excess observed around mature stars may be an indication of massive cometary populations existing in those systems

Runtime Enforcement of (Timed) Properties with Uncontrollable Events

Cette thèse étudie l’enforcement de propriétés temporisées à l’exécution en présence d’évènements incontrôlables. Les travaux se placent dans le cadre plus général de la vérification à l’exécution qui vise à surveiller l’exécution d’un système afin de s’assurer qu’elle respecte certaines propriétés. Ces propriétés peuvent être spécifiées à l’aide de formules logiques, ou au moyen d’autres modèles formels, parfois équivalents, comme des automates. Nous nous intéressons à l’enforcement à l’exécution de propriétés spécifiées par des automates temporisés. Tout comme la vérification à l’exécution, l’enforcement à l’exécution surveille l’exécution d’un système, la différence étant qu’un mécanisme d’enforcement réalise certaines modifications sur l’exécution afin de la contraindre à satisfaire la propriété souhaitée. Nous étudions plus particulièrement l’enforcement à l’exécution lorsque certains évènements de l’exécution sont incontrôlables, c’est-à-dire qu’ils ne peuvent pas être modifiés par un mécanisme d’enforcement. Nous définissons des algorithmes de synthèse de mécanismes d’enforcement décrits de manières fonctionnelle puis opérationnelle, à partir de propriétés temporisées régulières (pouvant être représentées par des automates temporisés). Ainsi, deux mécanismes d’enforcement équivalents sont définis, le premier présentant une approche correcte sans considération d’implémentation, alors que le second utilise une approche basée sur la théorie des jeux permettant de précalculer certains comportements, ce qui permet de meilleures performances. Une implémentation utilisant ce précalcul est également présentée et évaluée. Les résultats sont encourageant quant à la faisabilité de l’enforcement à l’exécution en temps réel, avec des temps supplémentaires suffisamment courts sur de petites propriétés pour permettre une utilisation de tels systèmes.This thesis studies the runtime enforcement of timed properties when some events are uncontrollable. This work falls in the domain of runtime verification, which includes all the techniques and tools based on or related to the monitoring of system executions with respect to requirement properties. These properties can be specified using different models such as logic formulae or automata. We consider timed regular properties, that can be represented by timed automata. As for runtime verification, a runtime enforcement mechanism watches the executions of a system, but instead of just outputting a verdict, it modifies the execution so that it satisfies the property. We are interested in runtime enforcement with uncontrollable events. An uncontrollable event is an event that an enforcement mechanism can not modify. We describe the synthesis of enforcement mechanisms, in both a functional and an operational way, that enforce some desired timed regular property. We define two equivalent enforcement mechanisms, the first one being simple, without considering complexity aspects, whereas the second one has a better time complexity thanks to the use of game theory; the latter being better suited for implementation. We also detail a tool that implements the second enforcement mechanism, as well as some performance considerations. The overhead introduced by the use of our tool seems low enough to be used in some real-time application scenarios

Enforcement à l’exécution de propriétés temporisées régulières en présence d’évènements incontrôlables

This thesis studies the runtime enforcement of timed properties when some events are uncontrollable. This work falls in the domain of runtime verification, which includes all the techniques and tools based on or related to the monitoring of system executions with respect to requirement properties. These properties can be specified using different models such as logic formulae or automata. We consider timed regular properties, that can be represented by timed automata. As for runtime verification, a runtime enforcement mechanism watches the executions of a system, but instead of just outputting a verdict, it modifies the execution so that it satisfies the property. We are interested in runtime enforcement with uncontrollable events. An uncontrollable event is an event that an enforcement mechanism can not modify. We describe the synthesis of enforcement mechanisms, in both a functional and an operational way, that enforce some desired timed regular property. We define two equivalent enforcement mechanisms, the first one being simple, without considering complexity aspects, whereas the second one has a better time complexity thanks to the use of game theory; the latter being better suited for implementation. We also detail a tool that implements the second enforcement mechanism, as well as some performance considerations. The overhead introduced by the use of our tool seems low enough to be used in some real-time application scenarios.Cette thèse étudie l’enforcement de propriétés temporisées à l’exécution en présence d’évènements incontrôlables. Les travaux se placent dans le cadre plus général de la vérification à l’exécution qui vise à surveiller l’exécution d’un système afin de s’assurer qu’elle respecte certaines propriétés. Ces propriétés peuvent être spécifiées à l’aide de formules logiques, ou au moyen d’autres modèles formels, parfois équivalents, comme des automates. Nous nous intéressons à l’enforcement à l’exécution de propriétés spécifiées par des automates temporisés. Tout comme la vérification à l’exécution, l’enforcement à l’exécution surveille l’exécution d’un système, la différence étant qu’un mécanisme d’enforcement réalise certaines modifications sur l’exécution afin de la contraindre à satisfaire la propriété souhaitée. Nous étudions plus particulièrement l’enforcement à l’exécution lorsque certains évènements de l’exécution sont incontrôlables, c’est-à-dire qu’ils ne peuvent pas être modifiés par un mécanisme d’enforcement. Nous définissons des algorithmes de synthèse de mécanismes d’enforcement décrits de manières fonctionnelle puis opérationnelle, à partir de propriétés temporisées régulières (pouvant être représentées par des automates temporisés). Ainsi, deux mécanismes d’enforcement équivalents sont définis, le premier présentant une approche correcte sans considération d’implémentation, alors que le second utilise une approche basée sur la théorie des jeux permettant de précalculer certains comportements, ce qui permet de meilleures performances. Une implémentation utilisant ce précalcul est également présentée et évaluée. Les résultats sont encourageant quant à la faisabilité de l’enforcement à l’exécution en temps réel, avec des temps supplémentaires suffisamment courts sur de petites propriétés pour permettre une utilisation de tels systèmes

Runtime enforcement of timed properties using games

International audienc

Runtime Enforcement Using Büchi Games

International audienceWe leverage Büchi games for the runtime enforcement of regular properties with uncontrollable events. Runtime enforcement consists in modifying the execution of a running system to have it satisfy a given regular property, modelled by an automaton. We revisit runtime enforcement with uncontrollable events and propose a framework where we model the runtime enforcement problem as a Büchi game and synthesise sound, compliant, and optimal enforcement mechanisms as strategies. We present algorithms and a tool implementing enforcement mechanisms. We reduce the complexity of the computations performed by enforcement mechanisms at runtime by pre-computing decisions of enforcement mechanisms ahead of time

GREP: Games for the Runtime Enforcement of Properties

Part 5: Testing Timed and Distributed SystemsInternational audienceWe present GREP, a tool for the runtime enforcement of (timed) properties. GREP takes an execution sequence as input (stdin), and modifies it (stdout) as necessary to enforce the desired property, when possible. GREP can enforce any regular timed property described by a deterministic and complete Timed Automaton. The main novelties of GREP are twofold: it uses game theory to improve the synthesis of enforcement mechanisms, and it accounts for uncontrollable events, i.e. events that cannot be controlled by the enforcement mechanisms and thus have to be released immediately. We present an overview of GREP and validate its usability with a performance evaluation