Towards a Scalable Dynamic Spatial Database System

With the rise of GPS-enabled smartphones and other similar mobile devices, massive amounts of location data are available. However, no scalable solutions for soft real-time spatial queries on large sets of moving objects have yet emerged. In this paper we explore and measure the limits of actual algorithms and implementations regarding different application scenarios. And finally we propose a novel distributed architecture to solve the scalability issues.Comment: (2012

Passage à l'échelle pour les mondes virtuels

Virtual worlds attract millions of users and these popular applications --supported by gigantic data centers with myriads of processors-- are routinely accessed. However, surprisingly, virtual worlds are still unable to host simultaneously more than a few hundred users in the same contiguous space.The main contribution of the thesis is Kiwano, a distributed system enabling an unlimited number of avatars to simultaneously evolve and interact in a contiguous virtual space. In Kiwano we employ the Delaunay triangulation to provide each avatar with a constant number of neighbors independently of their density or distribution. The avatar-to-avatar interactions and related computations are then bounded, allowing the system to scale. The load is constantly balanced among Kiwano's nodes which adapt and take in charge sets of avatars according to their geographic proximity. The optimal number of avatars per CPU and the performances of our system have been evaluated simulating tens of thousands of avatars connecting to a Kiwano instance running across several data centers, with results well beyond the current state-of-the-art.We also propose Kwery, a distributed spatial index capable to scale dynamic objects of virtual worlds. Kwery performs efficient reverse geolocation queries on large numbers of moving objects updating their position at arbitrary high frequencies. We use a distributed spatial index on top of a self-adaptive tree structure. Each node of the system hosts and answers queries on a group of objects in a zone, which is the minimal axis-aligned rectangle. They are chosen based on their proximity and the load of the node. Spatial queries are then answered only by the nodes with meaningful zones, that is, where the node's zone intersects the query zone.Kiwano has been successfully implemented for HybridEarth, a mixed reality world, Manycraft, our scalable multiplayer Minecraft map, and discussed for OneSim, a distributed Second Life architecture. By handling avatars separately, we show interoperability between these virtual worlds.With Kiwano and Kwery we provide the first massively distributed and self-adaptive solutions for virtual worlds suitable to run in the cloud. The results, in terms of number of avatars per CPU, exceed by orders of magnitude the performances of current state-of-the-art implementations. This indicates Kiwano to be a cost effective solution for the industry. The open API for our first implementation is available at \url{http://kiwano.li}.La réalité mixe, les jeux en ligne massivement multijoueur (MMOGs), les mondes virtuels et le cyberespace sont des concepts extrêmement attractifs. Mais leur déploiement à large échelle reste difficile et il est en conséquence souvent évité.La contribution principale de la thèse réside dans le système distribué Kiwano, qui permet à un nombre illimité d'avatars de peupler et d'interagir simultanément dans un même monde contigu. Dans Kiwano nous utilisons la triangulation de Delaunay pour fournir à chaque avatar un nombre constant de voisins en moyenne, indépendamment de leur densité ou distribution géographique. Le nombre d'interactions entre les avatars et les calculs inhérents sont bornés, ce qui permet le passage à l'échelle du système.La charge est repartie sur plusieurs machines qui regroupent sur un même nœud les avatars voisins de façon contiguë dans le graphe de Delaunay. L'équilibrage de la charge se fait de manière contiguë et dynamique, en suivant la philosophie des réseaux pair-à-pair (peer-to-peer overlays). Cependant ce principe est adapté au contexte de l'informatique dématérialisée (cloud computing).Le nombre optimal d'avatars par CPU et les performances de notre système ont été évalués en simulant des dizaines de milliers d'avatars connectés à la même instance de Kiwano tournant à travers plusieurs centres de traitement de données.Nous proposons également trois applications concrètes qui utilisent Kiwano : Manycraft est une architecture distribuée capable de supporter un nombre arbitrairement grand d'utilisateurs cohabitant dans le même espace Minecraft, OneSim, qui permet à un nombre illimité d'usagers d'être ensemble dans la même région de Second Life et HybridEarth, un monde en réalité mixte où avatars et personnes physiques sont présents et interagissent dans un même espace: la Terre

Kiwano: A scalable distributed infrastructure for virtual worlds

International audienceIn today's virtual worlds, even in the massively multi-player games, the number of avatars together in a virtual place barely reaches thousands. Regarding the billions of users dwelling the web, this is astonishingly low. In this paper we iden-tify spatial indexation as the bottleneck that impedes scalability and we propose Kiwano, a distributed system to scale up to millions and more. In order to split the load, Kiwano dynamically divides the space in zones, each having a server maintaining a spatial index of all moving objects within the zone. This allows to timely compute which objects are in the neighborhood of any avatar. Thus, knowing its immediate environment, the client is able compute the local scene

OneSim: Scaling Second Life with Kiwano

International audienceKiwano is a distributed infrastructure to scale virtual worlds developed within our team. OpenSim is an open source, enhanced implementation of Second Life servers. Combining these two systems we have designed OneSim, a distributed system to allow an unlimited number of users to be together in one sim: all players run a OpenSim instance of the same region populate with their respective neighboring avatars

Manycraft: Massively Distributed Minecraft

International audienceMinecraft is a popular game with more than 20 million paying users and many more playing the free version. However, in today's multiplayer mode, only a few thousand users can play together. For a common setting, when players cannot modify the map, we have designed a distributed system to scale the number of users. The Manycraft software runs on users' machines which communicate through Kiwano infrastructure. This paper describes its architecture and implementation. Manycraft node is available for download at http://manycraft.net, so we expect players to participate and join the demonstration at the given time slot

Big Ideas paper: Policy-driven middleware for a legally-compliant Internet of Things.

Internet of Things (IoT) applications, systems and services are subject to law. We argue that for the IoT to develop lawfully, there must be technical mechanisms that allow the enforcement of speci ed policy, such that systems align with legal realities. The audit of policy enforcement must assist the apportionment of liability, demonstrate compliance with regulation, and indicate whether policy correctly captures le- gal responsibilities. As both systems and obligations evolve dynamically, this cycle must be continuously maintained. This poses a huge challenge given the global scale of the IoT vision. The IoT entails dynamically creating new ser- vices through managed and exible data exchange . Data management is complex in this dynamic environment, given the need to both control and share information, often across federated domains of administration. We see middleware playing a key role in managing the IoT. Our vision is for a middleware-enforced, uni ed policy model that applies end-to-end, throughout the IoT. This is because policy cannot be bound to things, applications, or administrative domains, since functionality is the result of composition, with dynamically formed chains of data ows. We have investigated the use of Information Flow Control (IFC) to manage and audit data ows in cloud computing; a domain where trust can be well-founded, regulations are more mature and associated responsibilities clearer. We feel that IFC has great potential in the broader IoT context. However, the sheer scale and the dynamic, federated nature of the IoT pose a number of signi cant research challenges.Engineering and Physical Sciences Research Council (Grant ID: EP/K011510 CloudSafetyNet: End-to-End Application Security in the Cloud), Microsoft (through the Microsoft Cloud Computing Research Centre

Big Ideas paper: Policy-driven middleware for a legally-compliant Internet of Things.

Internet of Things (IoT) applications, systems and services are subject to law. We argue that for the IoT to develop lawfully, there must be technical mechanisms that allow the enforcement of speci ed policy, such that systems align with legal realities. The audit of policy enforcement must assist the apportionment of liability, demonstrate compliance with regulation, and indicate whether policy correctly captures le- gal responsibilities. As both systems and obligations evolve dynamically, this cycle must be continuously maintained. This poses a huge challenge given the global scale of the IoT vision. The IoT entails dynamically creating new ser- vices through managed and exible data exchange . Data management is complex in this dynamic environment, given the need to both control and share information, often across federated domains of administration. We see middleware playing a key role in managing the IoT. Our vision is for a middleware-enforced, uni ed policy model that applies end-to-end, throughout the IoT. This is because policy cannot be bound to things, applications, or administrative domains, since functionality is the result of composition, with dynamically formed chains of data ows. We have investigated the use of Information Flow Control (IFC) to manage and audit data ows in cloud computing; a domain where trust can be well-founded, regulations are more mature and associated responsibilities clearer. We feel that IFC has great potential in the broader IoT context. However, the sheer scale and the dynamic, federated nature of the IoT pose a number of signi cant research challenges

Recent advances in biosorption of heavy metals: support tools for biosorption equilibrium, kinetics and mechanism

Heavy metals are increasingly present in industrial wastes and effluents, which can generate serious concerns for environmental quality and human health. Consequently, there is a continuous expansion of researches for new approaches and developments to guarantee environmental cleaning-up. Although there are some physico-chemical established methods for the removal of heavy metals from various environmental compartments, biosorption gains further confidence as a reliable alternative compared to classical technologies, which are expensive and sometimes unreliable. This paper aims to analyze the biosorption as a biotechnological strategy for the decontamination of aqueous effluents containing heavy metal ions, in terms of its potential for metal immobilization and uptake. The paper also focuses on the most important parameters affecting the removal of heavy metals by various categories of biosorbents both living and non-living forms of biomass and provides new alternatives for modeling and optimization of process equilibrium and kinetics. A special attention was paid to biosorption mechanism, as a factual challenge for process optimization and scale-up. The potential benefits and problems associated to metal removal by biosorption are highlighted.Roumanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-ID-PCE-2011-3-0559”, Contract 265/2011

Chromium(VI) removal from aqueous solutions by Trichoderma viride fungal biomass

The bioremoval of Cr(VI) through biosorption and bioaccumulation using dead and living biomass of Trichoderma viride was investigated in batch mode, since a few studies were found in the literature on this subject. The biosorbent is an indigenous fungal strain of Trichoderma viride, isolated from a forest soil in an area from Iasi city, Romania. Effects of pH, biomass dosage, metal concentration in the initial solutions, contact time and temperature were assessed. It was found that the optimum pH for maximum removal efficiency is acidic for dead biomass and near the neutral value for living microorganisms. The biosorption process of total Cr removal by dead T. viride biomass is endothermic. The experimental data modeling and FTIR analysis showed that the mechanism of Cr(VI) removal by T. viride is based on a redox reaction. The linearized Langmuir isotherm had the best fitting compared to the other models applied showing that sorption occurs in monolayer at 25 and 40°C. Kinetic data were evaluated by the pseudo-first order and pseudo-second order adsorption kinetic models, together with pseudo-first order and pseudo-second order reduction models. The new fungal strain of T. viride has confirmed high uptakes and removal efficiencies in Chromium(VI) bioremoval