Bidirectional order dependencies (bODs) capture order relationships between lists of attributes in a relational table. They can express that, for example, sorting books by publication date in ascending order also sort...
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Bidirectional order dependencies (bODs) capture order relationships between lists of attributes in a relational table. They can express that, for example, sorting books by publication date in ascending order also sorts them by age in descending order. The knowledge about order relationships is useful for many data management tasks, such as query optimization, data cleaning, or consistency checking. Because the bODs of a specific dataset are usually not explicitly given, they need to be discovered. The discovery of all minimal bODs (in set-based canonical form) is a task with exponential complexity in the number of attributes, though, which is why existing bOD discovery algorithms cannot process datasets of practically relevant size in a reasonable time. In this paper, we propose the distributed bOD discovery algorithm DISTOD, whose execution time scales with the available hardware. DISTOD is a scalable, robust, and elastic bOD discovery approach that combines efficient pruning techniques for bOD candidates in set-based canonical form with a novel, reactive, and distributed search strategy. Our evaluation on various datasets shows that DISTOD outperforms both single-threaded and distributed state-of-the-art bOD discovery algorithms by up to orders of magnitude;it can, in particular, process much larger datasets.
The actor paradigm supports the natural expression of concurrency. It has inspired the development of several actor-based languages, whose adoption depends, to a large extent, on the runtime characteristics (i.e., the...
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ISBN:
(纸本)9781450369824
The actor paradigm supports the natural expression of concurrency. It has inspired the development of several actor-based languages, whose adoption depends, to a large extent, on the runtime characteristics (i.e., the performance and scaling behaviour) of programs written in these languages. This paper investigates the relative runtime characteristics of Akka, CAF and Pony, based on the Savina benchmarks. We observe that the scaling of many of the Savina benchmarks does not reflect their categorization (into essentially sequential, concurrent and parallel), that many programs have similar runtime characteristics, and that their runtime behaviour may drastically change nature (e.g., go from essentially sequential to parallel) by tweaking some parameters. These observations lead to our proposal of a single benchmark program which we designed so that through tweaking of some knobs (we hope) we can simulate most of the programs of the Savina suite.
The fast growth of cloud applications highlights the requirement of appropriate security controls to restrict access to shared resources limited to authorized users. Existing authorization systems are not primarily de...
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ISBN:
(纸本)9781479950638
The fast growth of cloud applications highlights the requirement of appropriate security controls to restrict access to shared resources limited to authorized users. Existing authorization systems are not primarily designed for cloud environments and do not provide the required flexibility, adaptability, elasticity, scalability, or fine-grainedness of cloud applications. This paper outlines an ongoing effort in development of a flexible fine-grained access control system for modern cloud based applications. Modern cloud applications are distinctive in that the required authorization rules are defined by the organizations owning data and resources, before the application logic can be developed by their programmers. Although this simplifies cloud application development and provides flexibility and adaptability to potential future policy changes, it highlights the need for an adaptive flexible authorization system.
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