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No description available.

The hardware landscape is currently changing from homogeneous multi-core systems towards heterogeneous systems with many di↵erent computing units, each with their own characteristics. This trend is a great opportunity for database systems to increase the overall performance if the heterogeneous resources can be utilized eciently. To achieve this, the main challenge is to place the right work on the right computing unit. Current approaches tackling this placement for query processing assume that data cardinalities of intermediate results can be correctly estimated. However, this assumption does not hold for complex queries. To overcome this problem, we propose an adaptive placement approach being independent of cardinality estimation of intermediate results. Our approach is incorporated in a novel adaptive placement sequence. Additionally, we implement our approach as an extensible virtualization layer, to demonstrate the broad applicability with multiple database systems. In our evaluation, we clearly show that our approach significantly improves OLAP query processing on heterogeneous hardware, while being adaptive enough to react to changing cardinalities of intermediate query results.

The Dresden Database Systems Group focuses on the advancement of data management techniques from a system level as well as information management perspective. With more than 15 PhD students the research group is involved in a variety of larger research projects ranging from activities to exploit modern hardware for scalable storage engines to advancing statistical methods for large-scale time series management. The group is visible at an international level as well as actively involved in cooperations with national and regional research partners

Sedan digitala bibliotekskataloger först introducerades i slutet av 60-talet och början av 70-talet har det funnits två skilda källor för metadata för bibliotek i Sverige. Å ena sidan Libris, utvecklad och använd av framför allt KB och forskningsbiblioteken, och å andra sidan Burk för folkbiblioteken. Nästan lika länge har det gjorts försök att skapa en gemensam, nationell katalog för alla svenska bibliotek, men trots alla ansträngningar, innefattande ett flertal direkt från regeringen, råder fortfarande det tvådelade systemet. Denna intervjustudie har till syfte att undersöka attityder hos anställda från olika delar av bibliotekssektorn i denna fråga. Även frågor om bibliotekssystem diskuteras. Det förefaller finnas stor enighet bland informanterna om att den bristande samordningen av katalogdata faktiskt är ett problem, men det råder delade meningar om vad som borde göras åt saken, och vem som borde göra det. Studien analyseras och sätts i ett sammanhang utifrån debatten om digital upphovsrätt i allmänhet och Tarleton Gillespies teorier i synnerhet. Slutsatser som dras är att samordning skulle underlättas om biblioteken använde sig av öppna data och öppen källkod, vilket skulle peka på Libris som källa för metadata och open source-bibliotekssystem som Koha. De bibliotek som har samordningsuppdrag, regionbiblioteken och KB, skulle behöva ta ett större ansvar för att samordning ska kunna komma till stånd. Om dessa förslag blev verklighet skulle leverantörerna behöva anpassa sina affärsmodeller för att kunna erbjuda data under öppna licenser. / Ever since digital library catalogues were first introduced in the late sixties and early seventies, there have been two separate metadata repositories for libraries in Sweden. On the one hand there is the Libris catalogue, developed and used mainly by the national library and the university libraries, and on the other hand there is the Burk catalogue for the local public libraries. For almost as long, attempts have been made to create a single, national catalogue for all Swedish libraries, but despite all efforts, including several government bills explicitly stating that this need to happen, the dual catalogue system prevails to this day. This interview study aims to find the opinions of people from different sectors of the library field on this matter. Views on integrated library systems are also debated. There seems to be great consensus among the interviewees that there is, in fact, a problem with lack of coordination of catalogues, but there is less agreement as to what should be done about it, and by whom. The study is analyzed and contextualized utilizing the debate on digital copyright in general and the theories of Tarleton Gillespie in particular. It is concluded that cooperation would be facilitated if libraries made use of open data and open source, which would suggest Libris as metadata repository and open source library systems such as Koha for ILS. Libraries assigned with interlibrary coordination, i.e. the regional and the national libraries, would have to take on a greater responsibility than the local libraries to implement these cooperations. Vendors serving libraries would have to adjust their business models if these proposals were to become reality to offer data under open licenses. / <p>QC 20230113</p>

No description available.

Multidatabases are being actively researched as a relatively new area in which many aspects are not yet fully understood. This area of transaction management in multidatabase systems still has many unresolved problems. The problem areas which this dissertation addresses are classification of multidatabase systems, global concurrency control, correctness criterion in a multidatabase environment, global deadlock detection, atomic commitment and crash recovery. A core group of research addressing these problems was identified and studied. The dissertation contributes to the multidatabase transaction management topic by introducing an alternative classification method for such multiple database systems; assessing existing research into transaction management schemes and based on this assessment, proposes a transaction processing model founded on the optimal properties of transaction management identified during the course of this research. / Computing / M. Sc. (Computer Science)

This thesis investigates the application of autonomic management to a distributed storage system. Effects on performance and resource consumption were measured in experiments, which were carried out in a local area test-bed. The experiments were conducted with components of one specific distributed storage system, but seek to be applicable to a wide range of such systems, in particular those exposed to varying conditions. The perceived characteristics of distributed storage systems depend on their configuration parameters and on various dynamic conditions. For a given set of conditions, one specific configuration may be better than another with respect to measures such as resource consumption and performance. Here, configuration parameter values were set dynamically and the results compared with a static configuration. It was hypothesised that under non-changing conditions this would allow the system to converge on a configuration that was more suitable than any that could be set a priori. Furthermore, the system could react to a change in conditions by adopting a more appropriate configuration. Autonomic management was applied to the peer-to-peer (P2P) and data retrieval components of ASA, a distributed storage system. The effects were measured experimentally for various workload and churn patterns. The management policies and mechanisms were implemented using a generic autonomic management framework developed during this work. The motivation for both groups of experiments was to test management policies with the objective to avoid unsatisfactory situations with respect to resource consumption and performance. Such unsatisfactory situations occur when either the P2P layer or the data retrieval mechanism is configured statically. In a statically configured P2P system two unsatisfactory situations can be identified. The first arises when the frequency with which P2P node states are verified is low and membership churn is high. The P2P node state becomes inaccurate due to a high membership churn, leading to errors during the routing process and a reduction in performance. In this situation it is desirable to increase the frequency to increase P2P state accuracy. The converse situation arises when the frequency is high and churn is low. In this situation network resources are used unnecessarily, which may also reduce performance, making it desirable to decrease the frequency. In ASA’s data retrieval mechanism similar unsatisfactory situations can be identified with respect to the degree of concurrency (DOC). The DOC controls the eagerness with which multiple redundant replicas are retrieved. An unsatisfactory situation arises when the DOC is low and there is a large variation in the times taken to retrieve replicas. In this situation it is desirable to increase the DOC, because by retrieving more replicas in parallel a result can be returned to the user sooner. The converse situation arises when the DOC is high, there is little variation in retrieval time and there is a network bottleneck close to the requesting client. In this situation it is desirable to decrease the DOC, since the low variation removes any benefit in parallel retrieval, and the bottleneck means that decreasing parallelism reduces both bandwidth consumption and elapsed time for the user. The experimental evaluations of autonomic management show promising results, and suggest several future research topics. These include optimisations of the managed mechanisms, alternative management policies, different evaluation methods, and the application of developed management mechanisms to other facets of a distributed storage system. The findings of this thesis could be exploited in building other distributed storage systems that focus on harnessing storage on user workstations, since these are particularly likely to be exposed to varying, unpredictable conditions.

<p>U radu se razmatra model sistema baziranog na Internet tehnologijama za psihometrijsku dijagnostiku.<br />Sistem je baziran na kombinaciji sistema za upravljanje sadržajem (Content Management Systems, CMS) i sistema za podr&scaron;ku grupnom radu (Computer Supported Cooperative Work, CSCW), omogućava dijagnostiku kognitivnih sposobnosti putem multimedijalnih testova, kontrolu nad tokom testiranja, skladi&scaron;tenje i analizu podataka o korisnicima i rezultata testova, kao i platformu za kolaborativni naučno istraživački rad.</p> / <p>In this thesis is analyzed model of system based on Internet technologies for psychometrics diagnostics.<br />System is based on combinations Content Management Systems, (CMS) and Computer Supported&nbsp;Cooperative Work, (CSCW). System enables: diagnostics cognitive capabilities using multimedial tests,&nbsp;control on process of diagnostics, recording data in databases, data analysis. System represent environment&nbsp;for collaborative scientific work.</p>

Le Système-de-Systèmes (SdS) devient l'un des principaux paradigmes pour l'ingénieriedes solutions de la prochaine génération, telles que les villes intelligentes, les bâtiments intelligents,les systèmes médicaux, les systèmes d'interventions d'urgence et les systèmes de défense. Parconséquent, l'intérêt apporté aux SdS, leur architecture et surtout leur sécurité est en croissancecontinue. Cependant, les caractéristiques de différenciation des SdS, telles que le comportementémergent et l'indépendance managériale et opérationnelle de ses constituants, peuvent introduiredes problèmes spécifiques qui rendent leurs modélisation, simulation et analyse de sécurité un déficritique. Dans cette thèse, nous étudions comment les approches du génie logiciel peuvent êtreétendues pour modéliser et analyser les architectures sécurisées de SdS, afin de découvrir lesattaques à fort impact (attaques en cascade) tôt à la phase d'architecture. Pour atteindre notreobjectif, nous proposons une méthode d'Ingénierie Dirigée par les Modèles (IDM), nommée Systems-of-Systems Security (SoSSec), qui comprend: (1) un langage de modélisation (SoSSecML) pour lamodélisation des architectures sécurisées des SdS, et une extension des Systèmes Multi-Agents(SMA) pour l'analyse des architectures sécurisées des SdS; (2) les outils correspondants: un éditeurgraphique, un générateur de code, une extension de la plate-forme Java Agent Development (JADE)pour la simulation des SMA, un outil personnalisé pour l'enregistrement des résultats de simulation;et (3) un processus pour guider l'utilisation de la méthode SoSSec. Pour illustrer notre approche,nous avons réalisé un cas d'étude sur un bâtiment intelligent réel, le bâtiment de l'école de santé del'Université d'Adélaïde (AHMS). / Systems-of-Systems (SoS) is becoming one of the major paradigm forengineering next generation solutions such as smart cities, smart buildings, health-care, emergencyresponse and defense. Therefore, there is a growing interest in SoS, their architecture and speciallytheir security. However, SoS differentiating characteristics, such as emergent behavior andmanagerial and operational independence of its constituents, may introduce specific issues thatmake their security modeling, simulation and analysis a critical challenge. In this thesis we investigatehow Software Engineering approaches can be extended to model and analyze secure SoS solutionsfor discovering high impact attacks (cascading attacks) at the architecture stage. In order to achieveour objective, we propose a Model Driven Engineering method, Systems-of-Systems Security(SoSSec), that comprises: (1) a modeling description language (SoSSecML) for secure SoS modelingand an extension of Multi-Agent Systems (MAS) for secure SoS architecture analysis, (2) thecorresponding tools: a graphical editor, a code generator, an extension of the Java AgentDevelopment (JADE) MAS simulation framework, a custom logging tool, (3) an utilization process toguide the use of the SoSSec method. To illustrate our approach we conducted a case study on a reallifesmart building SoS, the Adelaide University Health and Medical School (AHMS).