The Department of Computer Science at the University of Cyprus cordially invites you to the Colloquium entitled:

Diverse and Proportional Size-l Object Summaries for Keyword Search


Speaker: Dr. Georgios J. Fakas
Affiliation: Hong Kong University of Science and Technology, Hong Kong
Category: Colloquium
Location: Room 148, Faculty of Pure and Applied Sciences (FST-01), 1 University Avenue, 2109 Nicosia, Cyprus (directions)
Date: Wednesday, April 8, 2015
Time: 11:00-12:00 EET
Host: Marios Dikaiakos (

The abundance and ubiquity of big graphs (e.g., Online Social Networks such as Google+ and Facebook; bibliographic graphs such as DBLP) necessitates the effective and efficient search over them. Given a set of keywords that can identify a Data Subject (DS), a recently proposed relational keyword search paradigm produces, as a query result, a set of Object Summaries (OSs). An OS is a tree structure rooted at the DS node (i.e., a tuple containing the keywords) with surrounding nodes that summarize all data held on the graph about the DS. OS snippets, denoted as size-l OSs, have also been investigated. Size-l OSs are partial OSs containing l nodes such that the summation of their importance scores results in the maximum possible total score. However, the set of nodes that maximize the total importance score may result in an uninformative size-l OSs, as very important nodes may be repeated in it, dominating other representative information. In view of this limitation, in this paper we investigate the effective and efficient generation of two novel types of OS snippets, i.e. diverse and proportional size-l OSs, denoted as DSize-l and PSize-l OSs. Namely, apart from the importance of each node, we also consider its frequency in the OS and its repetitions in the snippets. We conduct an extensive evaluation on two real graphs (DBLP and Google+). We verify effectiveness by collecting user feedback, e.g. by asking DBLP authors (i.e. the DSs themselves) to evaluate our results. In addition, we verify the efficiency of our algorithms and evaluate the quality of the snippets that they produce.

Short Bio:
Georgios J. Fakas is a Post-Doctoral Research Fellow in the Department of Computer Science and Engineering at the Hong Kong University of Science and Technology. He also worked as a Senior Lecturer at the Manchester Metropolitan University, UK and as a Research Fellow at the University of Hong Kong, Hong Kong and at the Swiss Federal Institute of Technology - Lausanne (EPFL), Switzerland. He obtained his Ph.D. in Computation in 1998 from the Department of Computation, UMIST, Manchester, UK. His research interests include databases, keyword search and ranking.

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