Repair-Oriented Relational Schemas for Multidimensional Databases
Prof. Leopoldo Bertossi
DEI - Sala Seminari
24 aprile 2012
Summarizability in a multidimensional (MD) database refers to the correct reusability of pre-computed aggregate queries (or views) when computing higher-level aggregations or rollups. A dimension instance has this property if and only if it is strict and homogeneous. A dimension instance may fail to satisfy either of these two semantics conditions, and has to be repaired, restoring strictness and homogeneity. In this work, we take a relational approach to the problem of repairing dimension instances. A dimension repair is obtained by translating the dimension instance into a relational instance, repairing the latter using established techniques in the relational framework, and properly inverting the process. We show that the common relational star and snowflake schemas for MD databases are not the best choice for this process. Actually, for this purpose, we propose and formalize the path relational schema, which becomes the basis for obtaining dimensional repairs. The path schema turns out to have useful properties in general, as a basis for a relational representation and implementation of MD databases and data warehouses. It is also particularly suitable for restoring MD summarizability through relational repairs. We compare the dimension repairs so obtained with existing repair approaches for MD databases.
Joint work with Mahkameh Yaghmaie and Sina Ariyan.
Leopoldo Bertossi has been Full Professor at the School of Computer Science, Carleton University (Ottawa, Canada) since 2001. He is Faculty Fellow of the IBM Center for Advanced Studies (IBM Toronto Lab). He obtained a PhD in Mathematics from the Pontifical Catholic University of Chile (PUC) in 1988.
He has been the theme leader for "Adaptive Data Quality and Data Cleaning" of the "NSERC Strategic Network for Data Management for Business Intelligence" (BIN), a project that involves more than fifteen academic researchers across Canada plus several industrial partners.
Until 2001 he was professor and departmental chair (1993-1995) at the Department of Computer Science, PUC; and also the President of the Chilean Computer Science Society (SCCC) in 1996 and 1999-2000.
He has been visiting professor at the computer science departments of the universities of Toronto (1989/90), Wisconsin-Milwaukee (1990/91), Marseille-Luminy (1997) andvisiting researcher at the Technical University Berlin
(1997/98), visiting researcher and professor at the Free University of Bolzano-Bozen (Italy). In 2006 he was a visiting researcher at the Technical University of Vienna as a Pauli Fellow of the "Wolfgang Pauli Institute (WPI) Vienna".
Prof. Bertossi's research interests include database theory, data integration, peer data management, semantic web, intelligent information systems, data quality for business intelligence, knowledge representation, logic programming, and computational logic.
Area di ricerca:
Web, multimedia e database