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Session17 - CSCI585 Multidimensional Databases Cyrus...

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CSCI585 C. Shahabi Multidimensional Databases Cyrus Shahabi Computer Science Department University of Southern California [email protected]
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CSCI585 C. Shahabi Outline square6 Definitions (from A.R. 20 and 21) square6 Focus Application: OLAP square6 Prefix-Sum (from A.R. 16) square6 Dynamic Data Cube (from A.R. 17) square6 Iterative Data Cube (from A.R. 18) square6 Wavelet-based approaches rhombus6 Compact Data Cube (from A.R. 19) rhombus6 ProPolyne (from A.R. 22 and 23)
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CSCI585 C. Shahabi Definitions square6 During the past decade, the multidimensional data model emerged for use when the objective is to analyze data rather than to perform online transactions. square6 In contrast to previous technologies, these databases view data as multidimensional cubes that are particularly well suited for data analysis. square6 Multidimensional data models have three important application areas within data analysis: rhombus6 Data warehouses are large repositories that integrate data from several sources in an enterprise for analysis. rhombus6 Online analytical processing (OLAP) systems provide fast answers for queries that aggregate large amounts of detail data to find overall trends. rhombus6 Data mining applications seek to discover knowledge by searching semi-automatically for previously unknown patterns and relationships in multidimensional databases.
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CSCI585 C. Shahabi Definitions… square6 Multidimensional databases view data as cubes that generalize spreadsheets to any number of dimensions. square6 In addition, cubes support hierarchies in dimensions and formulas without duplicating their definitions. square6 A collection of related cubes comprises a multidimensional database or data warehouse. square6 Dimensions are used for selecting and aggregating data at the desired level of detail. square6 A dimension is organized into a containment-like hierarchy composed of numerous levels, each representing a level of detail required by the desired analyses. square6 Each instance of the dimension, or dimension value, belongs to a particular level.
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CSCI585 C. Shahabi Definitions … square6 Facts represent the subject—the interesting pattern or event in the enterprise that must be analyzed square6 In most multidimensional data models, facts are implicitly defined by their combination of dimension values; a fact exists only if there is a nonempty cell for a particular combination of values. square6 A measure consists of two components: rhombus6 a fact’s numerical property, such as the sales price or profit rhombus6 a formul a, usually a simple aggregation function such as sum , that can combine several measure values into one. square6 In a multidimensional database, measures generally represent the properties of the fact that the user wants to optimize. Measures then take on different values for various dimension combinations.
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