6533b7ddfe1ef96bd12744fd

RESEARCH PRODUCT

Semi-automatic conception and implementation of data warehouses : application to ecological data

subject

description

This thesis concerns the semi-automatic design of data warehouses and the associated OLAP cubes analyzing ecological data.The biological sciences, including ecology and agronomy, generate data that require an important collection effort: several years are often required to obtain a complete data set. Moreover, objects and phenomena studied by these sciences are complex and require many parameter recording to be understood. Finally, the collection of complex data over a long time results in an increased risk of inconsistency. Thus, these sciences generate numerous and heterogeneous data, which can be inconsistent. It is interesting to offer to scientists, who work in life sciences, information systems able to store and restore their data, particularly when those data have a significant volume. Among the existing tools, business intelligence tools, including online analytical systems (On-Line Analytical processing: OLAP), particularly caught our attention because it is data analysis process working on large historical collections (i.e. a data warehouse) to provide support to the decision making. The business intelligence offers tools that allow users to explore large volumes of data, in order to discover patterns and knowledge within the data, and possibly confirm their hypotheses.However, OLAP systems are complex information systems whose implementation requires advanced skills in business intelligence. Thus, although they have interesting features to manage and analyze multidimensional data, their complexity makes them difficult to manage by potential users, who would not be computer scientists.In the literature, several studies have examined the automatic multidimensional design, but the examples provided by theses works were traditional data. Moreover, other articles address the multidimensional modeling adapted to complex data (inconsistency, heterogeneous data, spatial objects, texts, images within a warehouse ...) but the proposed methods are rarely automatic. The aim of this thesis is to provide an automatic design method of data warehouse and OLAP cubes. This method must be able to take into account the inherent complexity of biological data. To test the prototypes, that we proposed in this thesis, we have prepared a data set concerning bird abundance along the Loire. This data set is structured as follows: (1) we have the census of 213 bird species (described with a set of qualitative factors, such as diet) in 198 points along the river for 4 census campaigns; (2) each of the 198 points is described by a set of environmental variables from different sources (land surveys, satellite images, GIS). These environmental variables address the most important issue in terms of multidimensional modeling. These data come from different sources, sometimes independent of bird census campaigns, and are inconsistent in time and space. Moreover, these data are heterogeneous: they can be qualitative factors, quantitative varaibles or spatial objects. Finally, these environmental data include a large number of attributes (158 selected variables) (...).