Keynote presentation by Timos Sellis
"Personalization in web search and data management"
Timos Sellis, Research Center "Athena" and National Technical Univ. of Athens (joint work with T. Dalamagas, G. Giannopoulos and A. Arvanitis)
We address issues on web search personalization by exploiting users' search histories to train and combine multiple ranking models for result reranking. These methods aim at grouping users' clickthrough data (queries, results lists, clicked results), based either on content or on specific features that characterize the matching between queries and results and that capture implicit user search behaviors. After obtaining clusters of similar clickthrough data, we train multiple ranking functions (using Ranking SVM model), one for each cluster. Finally, when a new query is posed, we combine ranking functions that correspond to clusters similar to the query, in order to rerank/personalize its results.
We also present how to support personalization in data management systems by providing users with mechanisms for specifying their preferences. In the past, a number of methods have been proposed for ranking tuples according to user-specified preferences. These methods include for example top-k, skyline, top-k dominating queries etc. However, neither of these methods has attempted to push preference evaluation inside the core of a database management system (DBMS). Instead, all ranking algorithms or special indexes are offered on top of a DBMS, hence they are not able to exploit any optimization provided by the query optimizer. In this talk we present a framework for supporting user preference as a fist-class construct inside a DBMS, by extending relational algebra with preference operators and by appropriately modifying query plans based on these preferences.
Prof. Timos Sellis received his diploma degree in Electrical Engineering in 1982 from the National Technical University of Athens (NTUA), Greece. In 1983 he received the M.Sc. degree from Harvard University and in 1986 the Ph.D. degree from the University of California at Berkeley, both in Computer Science. In 1986, he joined the Department of Computer Science of the University of Maryland, College Park as an Assistant Professor, and became an Associate Professor in 1992. Between 1992 and 1996 he was an Associate Professor at NTUA, where he is currently a Full Professor. Prof. Sellis is also the Director of the Institute for the Management of Information Systems (IMIS) of the "Athena" Research Center (www.imis.athena-innovation.gr). His research interests include data streams, peer-to-peer database systems, personalization, the integration of Web and databases, and spatio-temporal database systems. He has published over 190 articles in refereed journals and international conferences in the above areas and has been invited speaker in major international events. Prof. Sellis is a recipient of the prestigious Presidential Young Investigator (PYI) award given by the President of USA to the most talented new researchers (1990), and of the VLDB 1997 10 Year Paper Award for his work on spatial databases. He was the president of the National Council for Research and Technology of Greece (2001-2003) and a member of the VLDB Endowment (1996-2000). In November 2009, he was awarded the status of IEEE Fellow, for his contributions to database query optimization, and spatial data management. He has also participated and co-ordinated several national and european research projects.