Nov DOLAP 2002 McLean USA A Multidimensional and Multiversion Structure for OLAP Applications Mathurin Body 1,2, Maryvonne Miquel 2, Yvan Bédard 1,2, Anne Tchounikine 2 1 Centre de recherche en Géomatique, Univ Laval, Québec, Canada 2 Institut National des Sciences Appliquées, Lyon, France

Nov DOLAP 2002 McLean USA Purpose Handle evolutions in Multidimensional Structures Compare data into static structures Provide a new conceptual model Define evolution operators Give solutions and tools for implementation

Nov DOLAP 2002 McLean USA Multidimensional Models Date Gender CityCountry Static organization of data Fact Table Nb of Births Star or Snowflake representation Issues

Nov DOLAP 2002 McLean USA First Case Study Location dimension: D1100 D D Query: « Total number of births per year and city ? » Evo C  C  Evo C  C  Evo C1100  C2150  C1C2 D1D2D C1C2 D1D2D Exact view2. Mapped info into 2001 organization 3. Mapped info into 2002 organization Issues

Nov DOLAP 2002 McLean USA Second Case Study Location dimension: D100- D1-150 D2-50 Query: « Total number of births per year and district ? » Evo D100-? D1-150? D2-50? Evo D  Evo D140 * 150  D260 ** 50  C1 D Exact view2. First Structure3. Second Structure 2002 C1 D1D2 * D1 ~ 40 % of the births of D1 ** D2 ~ 60 % of the births of D1 Issues

Nov DOLAP 2002 McLean USA Existing Solutions (1/2) Related works Updating models (M. Blaschka, C. Hurtado, A.O. Mendelzon and A. Vaisman) +Pragmatic way +Allow temporal comparison –Corrupt data –lose data (e.g. deletion of a member) –Hiding evolutions

Nov DOLAP 2002 McLean USA Existing Solutions (2/2) Related works Tracking history models (R. Bliujute, P. Chamoni and S. Stock, J. Eder and C. Koncilia, R. Kimball, A.O. Mendelzon and A. Vaisman, T.B. Pedersen, C.S. Jensen and C.E. Dyreson ) +Temporally consistent representation +Evolutions kept –Only one representation of data (no comparison across time) –Limit of data analysis +Mapping functions (J. Eder and C. Koncilia) +Timestamps on the elements of multidimensional database (A.O. Mendelzon and A. Vaisman)

Nov DOLAP 2002 McLean USA Our Objectives For the administrators: –Integrate all kinds of evolution in a multidimensional structure –Take into account complex dimension structures For the users: –Choose between different modes of representation –End user tools for analyse Proposal

Nov DOLAP 2002 McLean USA Evolutions in multidimensional structures Proposal Dimension schema evolution Creation and deletion of a dimension Creation and deletion of a hierarchy Creation and deletion of a level Move of a level in the hierarchical schema structure Evolution members: simple operations Creation of a member Deletion of a member Transformation of a member (change of an attribute, its name or meaning…) Merging of n members into one member Splitting of one member into n members Reclassification of a member in the dimension structure Evolution on members : Exples of complex operations Decreasing: splitting and deletion Increasing: creation and merging Partial annexation: splitting and merging

Nov DOLAP 2002 McLean USA Conceptual Model: Temporal Multidimensional Schema ZaïreDem. Rep. of Congo [1990 ; 1997][1997 ; Now] Temporal Dimension: - Evolution of the hierarchical structure of the members Mapping Relationship: -keeping transition links between member versions D1 D D2 f : x  x f : x  0.4 x f : x  0.6 x f : x  x Confidence factor: -Evaluation of the confidence associated to a mapping (exact mapping) (approximated mapping) (exact mapping) (approximated mapping) - Evolution of the members of a dimension Member Version: V1 D1D2D3 [98 ; 02] [98 ; 00][01 ; 02] V2 P1 Proposal

Nov DOLAP 2002 McLean USA Conceptual Model: MultiVersion Fact Table Temporal Modes of Presentation: - Modes for the presentation of a multidimensional request MultiVersion Fact Table: -Fact Table with different temporal modes of Presentation - Automatically deduced from the temporally consistent fact table, the temporal dimensions and the mapping relationship - a valid, unchanged structure over its given valid time. Structure Version: VS.1VS.2VS.3 - Temporally consistent mode - version VS.1 - version VS.2 - version VS.3 Proposal

Nov DOLAP 2002 McLean USA Logical Model - Temporal Modes of Presentation integrated in a new dimension. Date Gender CityCountry Fact Table Nb of births Confidence factor - Confidence factors integrated as a new measure T.M.P. Implementation

Nov DOLAP 2002 McLean USA Architecture MultiVersion Data Warehouse OLAP MultiVersion CubeTemporal Data Warehouse -Extract the Structure Versions -Compute the transitive… of the Mapping relation -Mapping of data -Data Agregation -Multidimensional Indexation Implementation

Nov DOLAP 2002 McLean USA Prototype Sale numbers and production cost per product, district and month Star Schema of the temporal Data Warehouse Implementation

Nov DOLAP 2002 McLean USA Development Tools Visual Basic Interface and Proclarity Components OLAP MultiVersion Cube (SQL Server Analysis Service) Access to the data cube Data warehouse Repository (SQL Server) Access to meta data Implementation

Nov DOLAP 2002 McLean USA End User Tools for Analysis Implementation Example of Metadata: describes the evolutions of the element pointed in the grid. Grid: presents the values and their confidence factors Comparative study: Two temporal modes are represented Dimensions control: used to navigate trough the cube

Nov DOLAP 2002 McLean USA End User Tools for Navigation: find the « best version » Implementation Parameters for each type of confidence Rank of the temporal modes of presentation

Nov DOLAP 2002 McLean USA Conclusion A temporal multidimensional model for supporting evolutions on multidimensional structures USER Navigate through different modes of presentation Choose the interpretation he wants to give to his request Be guide to select its best representation Have access to metadata describing all evolutions of member versions DESIGNER AND ADMINISTRATOR Model different kinds of hierarchical dimensions Take into account all types of evolutions in the multidimensional structures Implement this model on commercial OLAP environment Extension choose a temporal mode of presentation for each dimension