Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases

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Usually, OLAP(On Line Analytical Processing) systems provide data visualization through a multidimensionaldata model according to which a data fact is viewed as a mapping from a point in aspace of dimensions into one or more spaces of measures. Moreover, dimensions are organized inlevels which confo...

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Autor principal: Vaisman, Alejandro Ariel
Formato: Tesis Doctoral
Lenguaje:Español
Publicado: 2001
Acceso en línea:https://hdl.handle.net/20.500.12110/tesis_n3331_Vaisman
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:tesis_n3331_Vaisman2023-10-03T12:38:52Z Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases Vaisman, Alejandro Ariel Usually, OLAP(On Line Analytical Processing) systems provide data visualization through a multidimensionaldata model according to which a data fact is viewed as a mapping from a point in aspace of dimensions into one or more spaces of measures. Moreover, dimensions are organized inlevels which conform a hierarchy, providing a way of defining different levels of data aggregation, acentral issue in data analysis. In a relational implementation of OLAP(usually called ROLAP), wecan think of facts as being stored in fact tables, while each dimension is described in a dimensiontable. The industry solutions were built under the assumption that data in fact tables reflect thedynamic aspect of the data warehouse, while data in dimension tables represent static information. However, if we think of the data warehouse as a materialized view of data located in multiplesources, it is usual to find situations in which the structure of these sources changes, a new sourceis added, or an old one dropped. Any of these changes may require updates to the structure ofsome dimensions. Further, as multidimensional views are designed according to requirements fromend users, a redefinition of the initial requirements may cause a dimension update. In this thesis we argue that accounting for dimension updates is necessary in an OLAP toolin order to avoid constantly rebuilding dimensions from scratch. Thus, we first characterize theseupdates and study the view maintenance problem when they occur. We developed algorithms which,taking advantage of the nature of the dimension updates, in some cases outperform well-known viewmaintenance algorithms. We then propose an extension to the MDX language(a standard querylanguage for OLAP) and describe the implementation of TSOLAP, a multidimensional repositorywhich supports dimension updates and view maintenance, developed following the OLE DB for OLAP standard. We discuss the experimental results of tests performed over a real-life case study,a medical center in Buenos Aires. In the second part of the thesis we embed our proposal in the temporal database framework,introducing the Temporal Multidimensional Data Model, and a temporal query language for OLAPwhich we called TOLAP. TOLAP allows expressing complex OLAP queries in an elegant anddeclarative fashion. We discuss issues like syntax, semantics, safety and expressive power. We alsopresent an implementation including a graphic environment for temporal OLAP. Finally, we showhow the temporal approach can be applied to the case study mentioned above. Fil: Vaisman, Alejandro Ariel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2001 Tesis Doctoral PDF Español info:eu-repo/semantics/openAccess https://creativecommons.org/licenses/by-nc-sa/2.5/ar https://hdl.handle.net/20.500.12110/tesis_n3331_Vaisman
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language Español
orig_language_str_mv Español
description Usually, OLAP(On Line Analytical Processing) systems provide data visualization through a multidimensionaldata model according to which a data fact is viewed as a mapping from a point in aspace of dimensions into one or more spaces of measures. Moreover, dimensions are organized inlevels which conform a hierarchy, providing a way of defining different levels of data aggregation, acentral issue in data analysis. In a relational implementation of OLAP(usually called ROLAP), wecan think of facts as being stored in fact tables, while each dimension is described in a dimensiontable. The industry solutions were built under the assumption that data in fact tables reflect thedynamic aspect of the data warehouse, while data in dimension tables represent static information. However, if we think of the data warehouse as a materialized view of data located in multiplesources, it is usual to find situations in which the structure of these sources changes, a new sourceis added, or an old one dropped. Any of these changes may require updates to the structure ofsome dimensions. Further, as multidimensional views are designed according to requirements fromend users, a redefinition of the initial requirements may cause a dimension update. In this thesis we argue that accounting for dimension updates is necessary in an OLAP toolin order to avoid constantly rebuilding dimensions from scratch. Thus, we first characterize theseupdates and study the view maintenance problem when they occur. We developed algorithms which,taking advantage of the nature of the dimension updates, in some cases outperform well-known viewmaintenance algorithms. We then propose an extension to the MDX language(a standard querylanguage for OLAP) and describe the implementation of TSOLAP, a multidimensional repositorywhich supports dimension updates and view maintenance, developed following the OLE DB for OLAP standard. We discuss the experimental results of tests performed over a real-life case study,a medical center in Buenos Aires. In the second part of the thesis we embed our proposal in the temporal database framework,introducing the Temporal Multidimensional Data Model, and a temporal query language for OLAPwhich we called TOLAP. TOLAP allows expressing complex OLAP queries in an elegant anddeclarative fashion. We discuss issues like syntax, semantics, safety and expressive power. We alsopresent an implementation including a graphic environment for temporal OLAP. Finally, we showhow the temporal approach can be applied to the case study mentioned above.
format Tesis Doctoral
author Vaisman, Alejandro Ariel
spellingShingle Vaisman, Alejandro Ariel
Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases
author_facet Vaisman, Alejandro Ariel
author_sort Vaisman, Alejandro Ariel
title Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases
title_short Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases
title_full Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases
title_fullStr Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases
title_full_unstemmed Actualización y mantenimiento de vistas en bases de datos multidimensionales = Updates and view maintenance in multidimensional databases
title_sort actualización y mantenimiento de vistas en bases de datos multidimensionales = updates and view maintenance in multidimensional databases
publishDate 2001
url https://hdl.handle.net/20.500.12110/tesis_n3331_Vaisman
work_keys_str_mv AT vaismanalejandroariel actualizacionymantenimientodevistasenbasesdedatosmultidimensionalesupdatesandviewmaintenanceinmultidimensionaldatabases
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