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Jungnickel Tim - One of the best experts on this subject based on the ideXlab platform.
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On the Feasibility of Multi-Leader Replication in the Early Tiers
Technische Universitaet Berlin (Germany), 2018Co-Authors: Jungnickel TimAbstract:In traditional service architectures that follow the service statelessness principle, the state is primarily held in the Data Tier. Here, service operators utilize tailored storage solutions to guarantee the required availability; even though failures can occur at any time. This centralized approach to store and process an application’s state in the Data Tier implies that outages of the entire Tier cannot be tolerated. An alternative approach, which is in focus of this thesis, is to decentralize the processing of state information and to use more stateful components in the early Tiers. The possibility to tolerate a temporary outage of an entire Tier implies that the application’s state can be manipulated by the remaining Tiers without waiting for approval from the unavailable Tier. This setup requires multi-leader replication, where every replica can accept writes and forwards the resulting changes to the other replicas. This thesis explores the feasibility of using multi-leader replication to store and process state in a decentralized manner across multiple Tiers. To this end, two replication mechanisms, namely Conflict-free Replicated Data Types and Operational Transformation, are under particular investigation. We use and extend both mechanisms to demonstrate that the aforementioned decentralization is worth considering when designing a service architecture. The challenges that arise when following our approach go back to fundamental impossibility results in distributed systems research, i.e. the impossibility to achieve a fault-tolerant consensus mechanism in asynchronous systems and the inevitable trade-off between availability and consistency in the presence of failures. With this thesis, we contribute to close the exposed gaps of both results by providing usable alternatives for standard IT services. We exemplify the feasibility of our alternatives with a fully distributed IMAP service and a programming library that provides the necessary extension to utilize our approach in a variety of web-based applications. All contributions of this thesis are based on both theory and practice. In particular, all extensions to the existing multi-leader replication mechanisms were proven to satisfy the necessary properties. Moreover, those extensions were also implemented as prototypical applications and evaluated against the corresponding de facto standard software from the industry
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Über die Realisierbarkeit von Multi-Leader Replikation in den frühen Softwareschichten
Berlin, 2018Co-Authors: Jungnickel TimAbstract:Published in print by Universitätsverlag der TU Berlin, ISBN 978-3-7983-3001-6 (ISSN 2199-5249)In traditional service architectures that follow the service statelessness principle, the state is primarily held in the Data Tier. Here, service operators utilize tailored storage solutions to guarantee the required availability; even though failures can occur at any time. This centralized approach to store and process an application’s state in the Data Tier implies that outages of the entire Tier cannot be tolerated. An alternative approach, which is in focus of this thesis, is to decentralize the processing of state information and to use more stateful components in the early Tiers. The possibility to tolerate a temporary outage of an entire Tier implies that the application’s state can be manipulated by the remaining Tiers without waiting for approval from the unavailable Tier. This setup requires multi-leader replication, where every replica can accept writes and forwards the resulting changes to the other replicas. This thesis explores the feasibility of using multi-leader replication to store and process state in a decentralized manner across multiple Tiers. To this end, two replication mechanisms, namely Conflict-free Replicated Data Types and Operational Transformation, are under particular investigation. We use and extend both mechanisms to demonstrate that the aforementioned decentralization is worth considering when designing a service architecture. The challenges that arise when following our approach go back to fundamental impossibility results in distributed systems research, i.e. the impossibility to achieve a fault-tolerant consensus mechanism in asynchronous systems and the inevitable trade-off between availability and consistency in the presence of failures. With this thesis, we contribute to close the exposed gaps of both results by providing usable alternatives for standard IT services. We exemplify the feasibility of our alternatives with a fully distributed IMAP service and a programming library that provides the necessary extension to utilize our approach in a variety of web-based applications. All contributions of this thesis are based on both theory and practice. In particular, all extensions to the existing multi-leader replication mechanisms were proven to satisfy the necessary properties. Moreover, those extensions were also implemented as prototypical applications and evaluated against the corresponding de facto standard software from the industry.Basierend auf dem “service statelessness principle” ist es üblich, Softwaredienste so zu entwerfen, dass der Zustand des Dienstes primär in einer gekapselten Datenschicht verarbeitet wird. Innerhalb der Datenschicht werden spezielle Lösungen verwendet, um die Verfügbarkeit der Daten sicherzustellen. Dieser zentralisierte Ansatz hat zur Folge, dass ein Ausfall oder eine temporäre Nichtverfügbarkeit der gesamten Datenschicht zwangsweise zur Nichtverfügbarkeit des gesamten Dienstes führt. Ein alternativer Ansatz, welcher in dieser Arbeit erforscht wird, ist die dezentralisierte Speicherung und Verarbeitung der Daten in den darüberliegenden Softwareschichten. Um in diesem Ansatz einen Ausfall der gesamten Datenschicht zu kompensieren, ist es zwingend notwendig, dass die verbleibenden Schichten die eingehenden Anfragen ohne die Bestätigung durch die Datenschicht beantworten können. Hierfür wird eine Replikationsarchitektur benötigt, in der jedes Replikat die Anfragen direkt beantworten kann; die so genannte “multi-leader replication”. In dieser Arbeit werden diese Replikationsarchitekturen verwendet, um den Zustand und die Daten eines Dienstes zu dezentralisieren und über mehrere Schichten zu replizieren. Hierbei werden zwei Mechanismen detaillierter betrachtet: “Conflict-free Replicated Data Types” und “Operational Transformation”. Anschließend werden beide Mechanismen erweitert und hinsichtlich der Verwendbarkeit für den beschriebenen Ansatz geprüft. Als Ergebnis dieser Arbeit wird gezeigt, dass ein dezentralisierter Ansatz mit den vorgestellten Mechanismen in Betracht gezogen werden kann. Die Herausforderungen, die bei der Anwendung dieses Ansatzes entstehen, basieren auf nachweislich unlösbaren Problemen aus der Forschung von Verteilten Systemen. Dazu gehört die Unlösbarkeit von Konsensus und die unausweichliche Abwägung zwischen Verfügbarkeit und Konsistenz in einem verteilten System mit Ausfällen. Diese Arbeit trägt dazu bei, die entstehenden Lücken, welche aus diesen fundamentalen Ergebnissen resulTieren, zu schließen und die vorgeschlagenen Lösungen für reale IT Dienste anwendbar zu machen. Dieses wird anhand eines dezentralen IMAP Dienstes und einer Programmierbibliothek für Webanwendungen verdeutlicht. Alle Bestandteile dieser Doktorarbeit verbinden Theorie und Praxis. Alle vorgeschlagenen Erweiterungen für bestehende Replikationssysteme werden in formalen Modellen verifiziert und prototypisch implemenTiert. Die ImplemenTierungen werden außerdem mit vergleichbarer Standardsoftware, welche dem heutigen Stand der Technik entspricht, in praktischen Experimenten evaluiert
Rini Setianingsih - One of the best experts on this subject based on the ideXlab platform.
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STATISTICAL LITERACY OF SECONDARY SCHOOL STUDENTS IN SOLVING CONTEXTUAL PROBLEMS TAKING INTO ACCOUNT THE INITIAL STATISTICAL ABILITY
'University of Kanjuruhan Malang', 2021Co-Authors: Risqi, Erlyanna Nur, Rini SetianingsihAbstract:Statistical literacy is strongly needed in the 21st century in reading Data information, thinking critically and making decisions. The purpose of this study is to describe the statistical literacy abilities of high school students in solving contextual problems taking into account their initial statistical abilities, with the following indicators, Tier 1 (reading & explaining Data), Tier 2 (analyzing, interpreting, interpreting critically, and making conclusions), Tier 3 (presenting Data and predicting something). This research is a qualitative in nature, using statistical ability test, statistical literacy test, and interview guidelines to collect Data. The subjects of this study consist of three female students of grade XII Senior High School, with high, medium and low initial statistical ability categories. The results of this study revealed that (1) The student with high initial statistical abilities can meet the indicators of Tier 1, Tier 2, Tier 3, so that she can be categorized at level 5 to 6 (critical-mathematics critical), (2) The student with medium ability can fulfil the Tier 1 indicator not fulfil the indicators in Tier 2 and Tier 3, so that it can be categorized at level 3 to 5 (Consistent noncritical-Critical), and (3) The students with low abilities can fulfill the indicators of Tier 1 not fulfil the indicators in Tier 2 and Tier 3, so that it can be categorized at level 1 to 3 (Idiosyncratic-Consistent Noncritical). Therefore, it is important for students and teachers to know statistical literacy skills in order to increase their understanding and ability to understand information in making decisions regarding daily problems
Zhang Jinlong - One of the best experts on this subject based on the ideXlab platform.
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Research of Lanzhou City Geological Disaster Mass Observation and Mass Prevention Informationization based on WebGIS
Remote Sensing Technology and Application, 2011Co-Authors: Zhang JinlongAbstract:Mass observation and mass prevention is the main technology of geological disaster mitigation in china.Utilizing network technology,communication technology and WebGIS technology to establish Lanzhou city geological disaster mass observation and mass prevention informationization system.This system is a significant method of scientific forecasting and early warning of geological disasters and mitigating the hazard of geological disaster.It consists of uploading Data module,analyzing disaster information module,publishing disaster information module and browsing disaster information module.Adopting three-Tier distributed architecture,namely,application Tier,business Tier and Data Tier as the system framework.System model library include the spatial prediction module of geological hazards and time prediction model of geological hazards.The relational Database,SQL Server2005,is the backend Database.Complete the development of the system by.NET platform.Running results show that the system is stable and can effectively service for all levels of users of the geological disaster mass observation and mass prevention system.
Hadi Alizadeh - One of the best experts on this subject based on the ideXlab platform.
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Development of a Framework for Applying ASYCUDA System with N-Tier Application Architecture
Software Engineering and Computer Systems, 2011Co-Authors: Ahmad Pahlavan Tafti, Safoura Janosepah, Nasser Modiri, Abdolrahman Mohammadi Noudeh, Hadi AlizadehAbstract:N-Tier architecture considered as a comprehensive and integrated solution for designing, creating, developing and maintaining the large scale applications. Each application is a set of several physical and logical components. If we want an enterprise application, we should design these components as a well formed layout. N-Tier application architecture provides a model for developers to create a flexible and reusable application. By breaking up an application into Tiers, developers only have to modify or add a specific layer, rather than have to rewrite the entire application over. There should be a presentation Tier, a business or Data access Tier, and a Data Tier. [1]
Risqi, Erlyanna Nur - One of the best experts on this subject based on the ideXlab platform.
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STATISTICAL LITERACY OF SECONDARY SCHOOL STUDENTS IN SOLVING CONTEXTUAL PROBLEMS TAKING INTO ACCOUNT THE INITIAL STATISTICAL ABILITY
'University of Kanjuruhan Malang', 2021Co-Authors: Risqi, Erlyanna Nur, Rini SetianingsihAbstract:Statistical literacy is strongly needed in the 21st century in reading Data information, thinking critically and making decisions. The purpose of this study is to describe the statistical literacy abilities of high school students in solving contextual problems taking into account their initial statistical abilities, with the following indicators, Tier 1 (reading & explaining Data), Tier 2 (analyzing, interpreting, interpreting critically, and making conclusions), Tier 3 (presenting Data and predicting something). This research is a qualitative in nature, using statistical ability test, statistical literacy test, and interview guidelines to collect Data. The subjects of this study consist of three female students of grade XII Senior High School, with high, medium and low initial statistical ability categories. The results of this study revealed that (1) The student with high initial statistical abilities can meet the indicators of Tier 1, Tier 2, Tier 3, so that she can be categorized at level 5 to 6 (critical-mathematics critical), (2) The student with medium ability can fulfil the Tier 1 indicator not fulfil the indicators in Tier 2 and Tier 3, so that it can be categorized at level 3 to 5 (Consistent noncritical-Critical), and (3) The students with low abilities can fulfill the indicators of Tier 1 not fulfil the indicators in Tier 2 and Tier 3, so that it can be categorized at level 1 to 3 (Idiosyncratic-Consistent Noncritical). Therefore, it is important for students and teachers to know statistical literacy skills in order to increase their understanding and ability to understand information in making decisions regarding daily problems
