Michael Bohlen – författare
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4 produkter
4 produkter
E-bok
PDF, Engelska, 2013408 kr
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State-of-the-art database systems manage and process a variety of complex objects, including strings and trees. For such objects equality comparisons are often not meaningful and must be replaced by similarity comparisons. This book describes the concepts and techniques to incorporate similarity into database systems. We start out by discussing the properties of strings and trees, and identify the edit distance as the de facto standard for comparing complex objects. Since the edit distance is computationally expensive, token-based distances have been introduced to speed up edit distance computations. The basic idea is to decompose complex objects into sets of tokens that can be compared efficiently. Token-based distances are used to compute an approximation of the edit distance and prune expensive edit distance calculations. A key observation when computing similarity joins is that many of the object pairs, for which the similarity is computed, are very different from each other. Filters exploit this property to improve the performance of similarity joins. A filter preprocesses the input data sets and produces a set of candidate pairs. The distance function is evaluated on the candidate pairs only. We describe the essential query processing techniques for filters based on lower and upper bounds. For token equality joins we describe prefix, size, positional and partitioning filters, which can be used to avoid the computation of small intersections that are not needed since the similarity would be too low.
Häftad, Engelska, 2013
374 kr
Skickas inom 10-15 vardagar
State-of-the-art database systems manage and process a variety of complex objects, including strings and trees. For such objects equality comparisons are often not meaningful and must be replaced by similarity comparisons. This book describes the concepts and techniques to incorporate similarity into database systems. We start out by discussing the properties of strings and trees, and identify the edit distance as the de facto standard for comparing complex objects. Since the edit distance is computationally expensive, token-based distances have been introduced to speed up edit distance computations. The basic idea is to decompose complex objects into sets of tokens that can be compared efficiently. Token-based distances are used to compute an approximation of the edit distance and prune expensive edit distance calculations. A key observation when computing similarity joins is that many of the object pairs, for which the similarity is computed, are very different from each other. Filters exploit this property to improve the performance of similarity joins. A filter preprocesses the input data sets and produces a set of candidate pairs. The distance function is evaluated on the candidate pairs only. We describe the essential query processing techniques for filters based on lower and upper bounds. For token equality joins we describe prefix, size, positional and partitioning filters, which can be used to avoid the computation of small intersections that are not needed since the similarity would be too low.
E-bok
PDF, Engelska, 2022457 kr
Läs direkt efter köp
State-of-the-art database systems manage and process a variety of complex objects, including strings and trees. For such objects equality comparisons are often not meaningful and must be replaced by similarity comparisons. This book describes the concepts and techniques to incorporate similarity into database systems. We start out by discussing the properties of strings and trees, and identify the edit distance as the de facto standard for comparing complex objects. Since the edit distance is computationally expensive, token-based distances have been introduced to speed up edit distance computations. The basic idea is to decompose complex objects into sets of tokens that can be compared efficiently. Token-based distances are used to compute an approximation of the edit distance and prune expensive edit distance calculations. A key observation when computing similarity joins is that many of the object pairs, for which the similarity is computed, are very different from each other. Filters exploit this property to improve the performance of similarity joins. A filter preprocesses the input data sets and produces a set of candidate pairs. The distance function is evaluated on the candidate pairs only. We describe the essential query processing techniques for filters based on lower and upper bounds. For token equality joins we describe prefix, size, positional and partitioning filters, which can be used to avoid the computation of small intersections that are not needed since the similarity would be too low.
E-bok
PDF, Engelska, 20051 459 kr
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The TCGOV 2005 international conference on e-government was held at the Free University of Bozen-Bolzano during March 2–4, 2005. The conference was initiated by the working group “Towards Electronic Democracy” (TED) of the European Science Foundation and was jointly organized by the Free University ofBozen-Bolzano,theMunicipalityofBozen-Bolzano,theTEDWorkingGroup, and the IFIP Working Group 8.5. The conference addressed a large spectrum of issues that are relevant and have to be investigated for a successful transition from the traditional form of government to a new form known as e-government. The main focus was on the following topics: – improving citizen participation and policy making (e-democracy) – government application integration – semantic Web technologies for e-government – security aspects for e-government services Two sessions were dedicated to e-democracy, an emerging area within- government that seeks to enhance democratic processes and provide increased opportunities for individuals and communities to be involved in governmental decisions.Thecontributionsofthesetwosessionscovermorefundamentalresults and insights as well as experiences from di?erent countries. Another focus was on government application integration and the use of - mantic Web technologies, which are important technical aspects on the agenda of e-government research. Di?erent architectures for the integration and orch- tration of distributed services and processes were presented along with two case studies. Three papers about Semantic Web technologies discussed the use of ontologies in e-government.