Graph-Based Trust Model for Evaluating Trust Using Subjective Logic

50 pagesBefore using a digital system, it is necessary to evaluate it according to different parameters. Lately trust emerged as a momentous aspect of evaluation. Evaluating trust in a system is a complex issue that becomes more challenging when systems use distributed architectures. In a previous work, we proposed SocioTrust, a trust model that is based on probability theory to evaluate trust in a system for an activity. In SocioTrust, trust values are considered as the probability, by which a trustor believes that a trustee behaves as expected. A limita- tion of using traditional probability is that users cannot express their uncertainties about some actors of their activity. In real situations, not everyone is in possession of all the necessary information to provide a dogmatic opinion about something or someone. Subjective logic thus emerged to facilitate the expression of trust as a subjective opinion with degrees of uncertainty. In this paper, we propose SubjectiveTrust, a graph-based trust model to evaluate trust in a system for an activity using subjective logic. The distinctive features of our proposal are (i) user's un- certainties are taken into account in trust evaluation and (ii) besides taking into account the trust in the different entities the user depends on to perform an activity, it takes into consideration the architecture of the system to determine its trust level

Trust Evaluation of a System for an Activity

International audienceWhen users need to perform a digital activity, they evaluate available systems according to their functionality, ease of use, QoS, and/or economical as- pects. Recently, trust has become another key factor for such evaluation. Two main issues arise in the trust management research community. First, how to de- fine the trust in an entity, knowing that this can be a person, a digital or a physical resource. Second, how to evaluate such value of trust in a system as a whole for a particular activity. Defining and evaluating trust in systems is an open problem because there is no consensus on the used approach. In this work we propose an approach applicable to any kind of system. The distinctive feature of our pro- posal is that, besides taking into account the trust in the different entities the user depends on to perform an activity, it takes into consideration the architecture of the system to determine its trust level. Our goal is to enable users to have a per- sonal comparison between different systems for the same application needs and to choose the one satisfying their expectations. This paper introduces our approach, which is based on probability theory, and presents ongoing results

System Modeling and Trust Evaluation of Distributed Systems

International audienceNowadays, digital systems are connected through complex architectures. These systems involve persons, physical and digital resources such that we can consider that a system consists of elements from two worlds, the social world and the digital world, and their relations. Users perform activities like chatting, buying, sharing data, etc. Evaluating and choosing appropriate systems involve aspects like functionality, performance, QoS, ease of use, or price. Recently, trust appeared as another key factor for such an evaluation. In this context, we raise two issues, (i) how to formalize the entities that compose a system and their relations for a particular activity? and (ii) how to evaluate trust in a system for this activity? This work proposes answers to both questions. On the one hand, we propose SOCIOPATH, a metamodel based on first order logic, that allows to model a system considering entities of the social and digital worlds and their relations. On the other hand, we propose two approaches to evaluate trust in systems, namely, SOCIOTRUST and SUBJECTIVETRUST. The former is based on probability the- ory to evaluate users’ trust in systems for a given activity. The latter is based on subjective logic to take into account uncertainty in trust values

Trust Approach Based on User's Activities

National audienceThe complexity of distributed systems continuously increases and their usage is widened into a variety of contexts. Users do several activities through these systems like sharing data, chatting, buying online, etc. Persons, hardware and software are involved in activities so we consider a system as the representation of two worlds, the social and the digital worlds. Trust plays an important role in helping users to analyze the danger or risk they incur when doing an activity. Research on trust notions has focused on the social entities where a trustee is a person or an organization of persons. Recent research analyzes trust toward the digital world i.e., technologies. We consider that having these two building blocks is not enough for a user to decide if she can confidently do an activity in a particular system. Such decision requires to consider the system organization as a whole because it determines whom and what would be involved in a user activity and how. This article focuses on this problem and provides first ideas for solution

Trust your Social Network According to Satisfaction, Reputation and Privacy

International audienceNowadays we are witnessing a massive usage of social networking sites (Facebook, MySpace, etc.). Those systems facilitate user interaction; however, they disregard users' wellbeing because users are forced to trust the network and to use the system without any guarantees. We consider that this is unacceptable in systems where users build the success of the network. In this work, we propose to study how to improve users' trust in the system in terms of reputation, privacy and satisfaction. Despite former separate studies, we argue that these notions are strongly linked and must be analyzed in a correlated way

SOCIOPATH: In Whom You Trust?

Distributed systems are getting more and more numerous, complex and used in a wide variety of applications. New solutions and new architectures arise (e.g., clouds) that support new functionalities (e.g., social networks) and pile up several software layers. This evolution implies new non negligible dependences increasing in the number of actors involved in the system (e.g., providers and users). Some undesirable dependences could be hidden by this layer stacking, implying a reduced transparency for users and a misunderstanding of her actual autonomy. Given that any software is directly dependent of the underlying layers, if any of these layers misbehaves, the given software may be unable to provide promised services. We argue that users should be aware of the potential risks resulting from their dependences. To be able to deduce those dependences, one should know the way the system works (architecture, involved resources, providers, participants, etc.). This would help to deduce the potential trust a user could or should have toward the system. We consider this of utmost importance, as professional efficiency and personal privacy could be compromised if untrusted actors control the access to resources. This work proposes SOCIOPATH, a generic meta-model that allows to expose hidden or implied relationships among participants in the digital world, which also introduce dependences at the social level. The notions presented in this approach are basics of many fields, like security, privacy, trust, sociology, economy and so forth. SOCIOPATH can be used in the evaluation process of a system as well as in its upstream design

SocioPath: Bridging the Gap between Digital and Social Worlds

International audienceIn everyday life, people use more and more digital resources (data, application systems, Internet, etc.) for all aspects of their life like administrative procedures, financial management, private exchanges, collaborative work, etc. This leads to non-negligible dependences on the digital distributed resources that reveal strong reliance at the social level, for instance on providers, physical or moral persons, of these resources. Users are often not aware of their real autonomy regarding the management of their digital resources. Thus, currently, people underestimate social dependences generated by the system architecture they use and the resulting potential risks. We argue that it is necessary to be aware of some key aspects of system's architectures to be able to know dependences. In this paper, we proposes SOCIOPATH, a generic meta-model to derive dependences generated by system's architecture. In particular, SOCIOPATH focuses on relations, like access, control, support, ownership, and so forth, among the different entities of the system (digital resources, hardware, persons, etc.). Enriched with deduction rules and definitions, SOCIOPATH allows to reveal the dependences of a person towards each entity in the system. SOCIOPATH could then be useful in the evaluation process of a system, as a modeling tool that bridges the gap between the digital and the social worlds

Mast Cells Induce Blood Brain Barrier Damage in SCD by Causing Endoplasmic Reticulum Stress in the Endothelium

Endothelial dysfunction underlies the pathobiology of cerebrovascular disease. Mast cells are located in close proximity to the vasculature, and vasoactive mediators released upon their activation can promote endothelial activation leading to blood brain barrier (BBB) dysfunction. We examined the mechanism of mast cell-induced endothelial activation via endoplasmic reticulum (ER) stress mediated P-selectin expression in a transgenic mouse model of sickle cell disease (SCD), which shows BBB dysfunction. We used mouse brain endothelial cells (mBECs) and mast cells-derived from skin of control and sickle mice to examine the mechanisms involved. Compared to control mouse mast cell conditioned medium (MCCM), mBECs incubated with sickle mouse MCCM showed increased, structural disorganization and swelling of the ER and Golgi, aggregation of ribosomes, ER stress marker proteins, accumulation of galactose-1-phosphate uridyl transferase, mitochondrial dysfunction, reactive oxygen species (ROS) production, P-selectin expression and mBEC permeability. These effects of sickle-MCCM on mBEC were inhibited by Salubrinal, a reducer of ER stress. Histamine levels in the plasma, skin releasate and in mast cells of sickle mice were higher compared to control mice. Compared to control BBB permeability was increased in sickle mice. Treatment of mice with imatinib, Salubrinal, or P-selectin blocking antibody reduced BBB permeability in sickle mice. Mast cells induce endothelial dysfunction via ER stress-mediated P-selectin expression. Mast cell activation contributes to ER stress mediated endothelial P-selectin expression leading to increased endothelial permeability and impairment of BBB. Targeting mast cells and/or ER stress has the potential to ameliorate endothelial dysfunction in SCD and other pathobiologies

Involvement of the hemorheology in the pathophysiology of sickle cell disease

Nous avons étudié les marqueurs hémorhéologiques, hématologiques et biochimiques chez des sujets drépanocytaires homozygotes SS (HbS/HbS) et hétérozygotes composites SC (HbS/HbC) dans deux cohortes, pédiatriques et adultes, de patients drépanocytaires, et ce, à travers 7 complications récurrentes de la drépanocytose : 2 appartenant au profil hémolytique (l’ulcère de jambes et la glomérulopathie) et 5 appartenant au phénotype visqueux/vaso-occlusif (l’hypertension artérielle, le syndrome thoracique aigu (STA), la crise vaso-occlusive (CVO), la rétinopathie et l’ostéonécrose). Nous avons montré que : 1) une viscosité sanguine et une déformabilité érythrocytaire élevées sont des facteurs de risques de CVO chez les enfants homozygotes ; 2) Une viscosité sanguine élevée est associée à une hypertension artérielle systémique relative chez des adultes SS ; 3) les enfants SC présente une fonction vasculaire mieux préservée que les enfants SS pour faire face à une augmentation de la viscosité sanguine ; 4) les patients adultes SS avec une ostéonécrose présentent une déformabilité érythrocytaire plus élevée que les patients sans ostéonécrose ; 5) une viscosité sanguine élevée est associée à la présence d’une rétinopathie chez les adultes SC mais pas chez les SS ; 6) les patients adultes SS présentant une glomérulopathie ont un taux d’hémolyse élevé, une déformabilité érythrocytaire réduite et des agrégats érythrocytaires très robustes ; 7) les patients adultes SS avec des ulcères de jambes récurrents ont un taux d’hémolyse accru et une déformabilité érythrocytaire réduite. De plus, nos travaux confirment que l’-thalassémie module les propriétés de déformabilité érythrocytaire, mais montrent pour la première fois qu’elle module aussi les propriétés d’agrégation érythrocytaire, et notamment la force des agrégats érythrocytaires. En conclusion, ces travaux permettent de préciser le rôle de la rhéologie sanguine dans un certain nombre de complications de la drépanocytose et d’enrichir le modèle préexistant divisant les complications de la drépanocytose selon 2 phénotypes : hémolytique versus visqueux/vaso-occlusif. Nous montrons pour la première fois que le phénotype hémolytique est caractérisé aussi par des anomalies de la rhéologie du globule rouge : rigidité accrue et agrégats érythrocytaire robustes.Hemorheological, hemathological, and biochemical marquers of patients with sickle cell anemia (SS) and patients with sickle cell SC disease (SC) were studied in 2 cohorts: children and adults. We focused on 7 recurrent complications: 5 belonging to the viscosity/vaso-occlusion phenotype (systemic hypertension, acute chest syndrome (ACS), vaso-occlusive crisis (VOC), retinopathy and osteonecrosis) and 2 belonging to the hemolytic phenotype (leg ulcer and glomerulopathy). Our results show that 1) high viscosity is associated with increased risk for VOC in SS children; 2) blood viscosity is increased in SS adults with systemic relative hypertension; 3) SC children have preserved vascular function compared to SS children; 4) SS adults with osteonecrosis are characterized by higher red blood cell (RBC) deformability than SS adults without osteonecrosis; 5) high blood viscosity is associated with retinopathy in SC adults but not in SS adults; 6) SS adults affected by glomerulopathy have high hemolytic rate, low RBC deformability and increased RBC aggregates strenght; 7) SS adults with recurrent leg ulcers have high hemolytic rate and reduced RBC deformability. Moreover, our studies shows that alpha-thalassemia modulate RBC deformability and RBC aggregation properties. In conclusion, this work shows for the first time that the hemolytic phenotype is characterized by an abnormal RBC rheology which may play a role in several sickle cell complications

Trust your Social Network According to Satisfaction, Reputation and Privacy

International audienceNowadays we are witnessing a massive usage of social networking sites (Facebook, MySpace, etc.). Those systems facilitate user interaction; however, they disregard users' wellbeing because users are forced to trust the network and to use the system without any guarantees. We consider that this is unacceptable in systems where users build the success of the network. In this work, we propose to study how to improve users' trust in the system in terms of reputation, privacy and satisfaction. Despite former separate studies, we argue that these notions are strongly linked and must be analyzed in a correlated way