Information Retrieval for Children: Search Behavior and Solutions Sergio Ra´ulDuarte Torres Graduation committee: Chairman and Secretary Prof. dr. P. M. G. Apers University of Twente, NL Promoters Prof. dr. P. M. G. Apers University of Twente, NL Prof. dr. T. W. C. Huibers University of Twente, NL Assistant promoter Dr. ir. D. Hiemstra University of Twente, NL Members Prof. dr. Alan Smeaton Dublin City University, Ireland Prof. dr. Arjen de Vries TU Delft / CWI, NL Prof. dr. Franciska de Jong University of Twente, NL Prof. dr. Dirk Heylen University of Twente, NL Dr. Jaime Arguello University of North Carolina at Chapel Hill, USA CTIT Ph.D. Thesis Series No. 14-295 Centre for Telematics and Information Technology University of Twente P.O. Box 217, 7500 AE Enschede, NL SIKS Dissertation Series No. 2014-03 The research reported in this thesis has been carried out under the auspices of SIKS, the Dutch Research School for Information and Knowledge Systems. ISBN 978-90-365-3618-9 ISSN 1381-3617 DOI 10.3990./1.9789036536189 Cover Design Avril Follega/Sergio Duarte Printed by Gildeprint Drukkerijen Copyright c 2014, Sergio Ra´ulDuarte Torres, Enschede, The Netherlands All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, without the prior written permission of the author. INFORMATION RETRIEVAL FOR CHILDREN: SEARCH BEHAVIOR AND SOLUTIONS DISSERTATION to obtain the degree of doctor at the University of Twente, on the authority of the rector magnificus, Prof. dr. H. Brinksma, on account of the decision of the graduation committee to be publicly defended on Friday, 14th of February, 2014 at 16.45 by Sergio Ra´ulDuarte Torres born on December 19, 1983 in Bogot´a,Colombia This dissertation is approved by: Prof. dr. P. M. G. Apers (promotor) Prof. dr. T. W. C. Huibers (promotor) Dr. ir. Djoerd Hiemstra (assistent-promotor) This thesis is dedicated to the loving memory of my beloved father. May his memory forever be a source of inspiration and blessings. Thanks for everything. Acknowledgements I have finally completed my doctoral thesis after something more than four years. It has been a long way with ups and downs, and foremost, with plenty of learning. In these pages I want to express my gratitude to the persons that sup- ported me, gave me a hand, and in general to the persons that provided me their company in this journey. All of them played and important role in the completion of this thesis and a very important role in making fun the time I spent developing this work. First at all, I want to thank my parents who did not only raise me and take care of me, but also always make their best efforts to make my dreams possible. I deeply appreciate the advices and company of my sister during the difficult moments. I am also very thankful to Avril for sharing her playful attitude and joy towards life, and of course, for designing the cover of this thesis. I would like to express my deepest gratitude and appreciation to my pro- moter Peter Apers and my co-promoter Theo Huibers, who gave me the opportunity to carry out the research presented in this thesis, and more importantly, for giving me the chance of becoming a doctor. Foremost, I want to thank my daily supervisor, Djoerd Hiemstra, for his continuous guidance, motivation, patience and vast knowledge. I am certain I would have not reached this point without his advises, and I am certain that I am better professional and person after his mentoring. Besides my supervisor, I would like to thank the other members of the committee: Dr. Alan Smeaton, Dr. Jaime Arguello, Dr. Arjen de Vries, Dr. Franciska de Jong and Dr Dirk Heylen, for their generous time and good will through the preparation and review of this thesis. I feel very honored to have such a distinguished and tough committee. I am also very grateful to all the members of the DB group. I would particularly like to thank Ida and Suse, who helped me in a myriad ways, from giving me tips about the Dutch life to let my PhD going all these months. I also really appreciate Jan's support with the IT issues. I greatly enjoyed the conversations about his trips, which were very encouraging. Many thanks to Riham who helped me to get along with the Dutch life during my first months in the Netherlands; to Rezwan for his company, especially during the first months of my staying in the UT; to Juan for all those conversations about technical and random stuff that came out every time I visited his office; to Zhemin and Mohammad for the nice conversations, and to Christoph, Mena, Brend, Victor, Iwe, Almer and Lei for their company during the daily life in the group. I own a very important debt to all the members of the PuppyIR project, from whom I did not only receive some tasks, but also plenty of feedback and enlightening moments. Particularly, I highly appreciate the construc- tive comments and warm encouragement of Arjen de Vries, Franciska de Jong, Ian Ruthven, Leif Azzopardi, Andreas Lingnau and Marie-Francine Moens. Many of those comments shape the structure of my thesis. I want to extend my appreciation to Carsten Eickhoff, Ric Glassey, Frans Van der Sluis and Tamara Polajnar for giving me the chance of cooperat- ing with them in some of the endeavors of the project and the publications that were the results of that effort. I also highly appreciate the guidance and tips provided by Hanna Jockmann-Mannak these months. I woud like to show my gratitude to Pavel, as a former member of the DB group and the PuppyIR project, for his mentoring at the beginning of my PhD, for his ideas, suggestions and most of all for his encouragement. An important part of my research was carried out at Yahoo! Labs in Barcelona. I want to thank all the members of the lab. Particularly, I am very thankful to Ricardo Baeza-Yates for facilitating my stay in the labs and I highly appreciate the discussions and feedback offered by Mounia Lalmas, first in the PuppyIR meetings and then in the labs. I owe sincere and earnest thankfulness to Ingmar, for his assistance and mentoring. I really appreciate his patience and tenacity, which helped me make the most of my time in the lab. I learned a big deal from him. I also want to thank Hugues Bouchard for making my stay in Barcelona lively and showing me all those funky places in G´otico.Thanks a lot to Marek, Luca, Eraldo, Bart, Ruth, Giorgos, Jannete and Michele for the fussball matches and for hanging out in the city. Special thanks to Erik for his company and especially for his geeky tips and jokes during our stay. I have many people to thank beyond the scope of the campus and the research world. Firstly, I want to say thank you to the Piepke community, a.k.a my housemates. I am very thankful to Robin, as a colleague and even more as a housemate, I really appreciate his advices and his friendship. I also want to thank Marga for her kindness and everlasting tolerance of all my Latin habits. I also appreciate the time as housemates with Danielle, and more recently with Hans, Diego and Vincent. In these long months there were two persons that were always there when I need them. I will be always in depth debt with Maral for keeping my sanity through all our conversations and good coffee moments. I am also very glad to have met Juan Jimenez from the very early stages of my PhD, he has been a great friend and a person I can always count on. I am also glad to be part of the Latin move of Enschede, including my year as a board member of La Voz. It was very rewarding to be part of the board along with Oscar, Teo, Diruji, John, Juan Carlos and Daniela. During my stay in Enschede I met wonderful people. I feel blessed for meeting Andrea, Andreita, Andreea and Adriana, for their friendship and dancing lessons. It was a pleasure to attend the gigs of Chilangos and Rimon, so thanks a lot to David, Oscar, Jorge, Diego and Gerard. It was great to count with Abraham, Cesar, Norma and Israel at lunchtime, especially because everybody else likes to have lunch too early. I thank Eduardo and Nayeli, for their company during my first months in En- schede and for encouraging me to play f´utbol, although it did not last long, it was great fun. I also enjoyed greatly the meetings with Vicky, Lorenzo, Jorge and Maite in all the parties and dinners. Talking about parties, I had some very nice moments in places like the Molly Malone and, of course, the Paddy's, particularly with Desmond, Juan Pablo, Nico, Ignacio, Marina, Pablo, Jenny, Arturo (both), Javier, and many of the persons I have mentioned so far. For the times I was back home, I have to thank los compas, for all the catching up, the f´utbol games, the drinking and their immense encour- agement. The company of Goyes, Barrantes, Juan Manuel, Juan Carlos, Lina, Lis, Raul and Camilo were refreshing and completely necessary to recharge my energies prior to every year in the Netherlands. Without those moments I am sure I would have taken much longer to finish this thesis. Among my compas, I am always in debt with David, who has filled me with motivation for so many years and who has been there all the time during my PhD, even in the long distance, his friendship has always been invaluable.