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Ph.D de

Ph.D
Group : Databases

Optimisation de requêtes olap et visualisation de résultats

Starts on 15/09/2007
Advisor : SPYRATOS, Nicolas

Funding : AM
Affiliation : Université Paris-Sud
Laboratory : LRI

Defended on 16/09/2011, committee :
* Mohand-Said HACID Professeur, Université Claude-Bernard Lyon 1
Rapporteur
* Dominique LAURENT Professeur, Université de Cergy-Pontoise
Rapporteur
* Michel De ROUGEMONT Professeur, Université Paris 2,
Examinateur
* François GOASDOUÉ Maitre de conférences, Université Paris-Sud 11
Examinateur
* Nicolas SPYRATOS Professeur, Université Paris-Sud 11
Directeur

Research activities :
   - Databases
   - Multidimensional databases

Abstract :
In this thesis, we explore different aspects of Data Warehousing and OLAP,
the common point of our proposals being the functional model for data
analysis. Our main objective is to use that model in studying three
different, but related aspects:

- query optimization through rewriting and cache management,
- query result visualization,
- mapping of a relational BCNF schema to a functional schema.

Query optimization and cache management is a crucial issue in query
processing in general, and in data warehousing in particular; and query
rewriting is one of the basic techniques for query optimization. We
establish derivability conditions for analytic functional queries, using a
partial pre-order over the set of queries. Then we provide a sound and
complete rewriting algorithm, as well as an optimized cache management
strategy, both based on the underlying functional model.
A second important aspect that we explore in the thesis is that of query
result visualization. We show the importance for the visualization to
reflect such essential features of the dataset as functional dependencies.
We show that the connection existing between data and visualization is
precisely the connection between their functional representations. We then
define a framework, whose objective is to establish such a connection for a
given dataset and a set of visualizations.
In addition to the analysis of the visualization process, we use the
functional data model as a guide for interactive visualization, and define
what we call a parametric visualization.
A third important aspect of our work is experimentation with the results
obtained in the thesis. In order to be able to analyze the data contained
in a Boyce-Codd Normal Form (BCNF) table, one can use the results obtained
in this thesis, provided that the schema of the table can be mapped to a
functional schema. We present such a mapping in this thesis. Once the
relational schema has been transformed into a functional schema, we can
take advantage of the query optimization and result visualization results
presented in the thesis. We have used this transformation in the
implementation of two prototypes in the context of two different projects.

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