Apostolos N. Papadopoulos is an Associate Professor of Computer Science at the School of Informatics of Aristotle University of Thessaloniki (AUTH). He received his five-year Diploma Degree in Computer Engineering and Informatics from the University of Patras, and his Ph.D. Degree in Informatics from the School of Informatics (AUTH). His research interests include Data Management, Data Mining, and Big Data Analytics. He has served as a track co-chair of ACM SAC DTTA (Database Technologies Techniques and Applications) Track from 2005 until now, as well as a PC member in several International Conferences related to Data Management and Data Mining. He has co-presented four tutorials in ASONAM 2015, EDBT/ICDT 2016, ICDM 2016, and ECML/PKDD 2017 on the “Core Decomposition of Networks.” The paper “SkyGraph: an algorithm for important subgraph discovery in relational graphs,” Proceedings of ECML/PKDD, Antwerp, Belgium, 2008, received the Best Knowledge Discovery Paper Award, whereas the paper“Metric-Based Top-k Dominating Queries,” Proceedings of the 17th International Conference on Extending Database Technology (EDBT), Athens, 2014, was selected as the best paper for publication in ACM Transactions on Database Systems. Based on Google Scholar, he has around 3200 citations in his research work.Eleftherios Tiakas received a B.Sc. in Mathematics (1994), a B.Sc. and an M.Sc. in Informatics (2006), and a Ph.D. in Informatics (2011), all the degrees from the Aristotle University of Thessaloniki (AUTH). During the period 2004–2017, he served as Teacher of Mathematics in Secondary Education. From 2011–2017, he served as Adjunct Lecturer with the School of Informatics of AUTH. Since 2017, he has been on the Laboratory Teaching Staff with the School of Informatics of AUTH. His areas of research interest include: Databases, Data Structures, Data Mining, Information Retrieval, Similarity Search, Social Networks, and Bioinformatics. He is the author/co-author of 30 articles published in international journals and conference proceedings, plus 2 book chapters. His publications have received over 600 citations. He participated in 11 research projects and programs funded by the European Union and Greece. Finally, he serves as a PC member and reviewer for several international journals and conferences.Theodoros Tzouramanis is an Assistant Professor in the Department of Computer Science and Biomedical Informatics of the University of Thessaly. He received a five-year Diploma Degree in Electrical and Computer Engineering and a Ph.D. in Informatics, both from the Aristotle University of Thessaloniki. Prior to his current position, he served from 2003–2019 as Lecturer and later as Assistant Professor in the Department of Information and Communication Systems Engineering of the University of the Aegean. He has also been teaching at the Hellenic Open University since 2005. His research interests focus on data management, data security, and privacy. More than50 articles of his work have appeared in refereed scientific journals, conference proceedings, and chapters in books.Nikolaos Georgiadisis a Ph.D. candidate at the School of Informatics of Aristotle University of Thessaloniki (AUTH). He has a B.Sc. in Software Engineering from the Technical University of Kavala and a M.Sc. in Information Systems from the School of Informatics of AUTH. His main research interests focus on efficient algorithmic techniques for Knowledge Discovery from Big Data. He has professional experience as a Software Engineer in the IT industry in various companies in Greece, Germany, and Switzerland for over 15 years.Yannis Manolopoulos is a Professor and Vice-rector of the Open University of Cyprus. He received a five-year Diploma Degree in Electrical Engineering and a Ph.D. in Computer Engineering, both from the Aristotle University of Thessaloniki (AUTH). He has been with the University of Toronto, the University of Maryland at College Park,the University of Cyprus, the Hellenic Open University, and AUTH, where he served as Head of the School of Informatics. He has also served as Rector of the University of Western Macedonia in Greece and Vice-Chair of the Greek Computer Society. His research interest focuses on Data Management. He has co-authored 5 monographs and 11 textbooks in Greek, as well as >300 journal and conference papers. He has received >14,700 citations from >2,200 distinct academic institutions (h-index=57). He has also received 5 best paper awards from SIGMOD, ECML/PKDD, MEDES (2), and ISSPIT conferences and has been invited as keynote speaker at 20 international events. He has served as the main co-organizer of several CORE A/B conferences: SSTD 2003, SSDBM 2004, ADBIS 2006, ICANN 2010, WISE 2013, CAISE 2014, TPDL 2017, DASFAA 2018, IDEAS 2019, WI 2019, and SOFSEM 2020. He has also acted as an evaluator for funding agencies in Austria, Canada, Cyprus, Czech Republic, Estonia, EU, Georgia, Greece,Hong-Kong, Israel, Italy, Lithuania, Poland, and Russia. Currently, he serves on the Editorial Boards of the following journals (among others): Information Systems, World Wide Web, Computer Journal, Data Science and Analytics, and Artificial Intelligence Tools.

• List of Figures.- List of Tables.- Preface.- Acknowledgments.- Introduction.- Skyline Queries.- Variations of Skyline Queries.- Top-??.- Applications of Dominance-Based Queries.- Bibliography.- Authors' Biographies.- Index.

Apostolos N. Papadopoulos is an Associate Professor of Computer Science at the School of Informatics of Aristotle University of Thessaloniki (AUTH). He received his five-year Diploma Degree in Computer Engineering and Informatics from the University of Patras, and his Ph.D. Degree in Informatics from the School of Informatics (AUTH). His research interests include Data Management, Data Mining, and Big Data Analytics. He has served as a track co-chair of ACM SAC DTTA (Database Technologies Techniques and Applications) Track from 2005 until now, as well as a PC member in several International Conferences related to Data Management and Data Mining. He has co-presented four tutorials in ASONAM 2015, EDBT/ICDT 2016, ICDM 2016, and ECML/PKDD 2017 on the “Core Decomposition of Networks.” The paper “SkyGraph: an algorithm for important subgraph discovery in relational graphs,” Proceedings of ECML/PKDD, Antwerp, Belgium, 2008, received the Best Knowledge Discovery Paper Award, whereas the paper“Metric-Based Top-k Dominating Queries,” Proceedings of the 17th International Conference on Extending Database Technology (EDBT), Athens, 2014, was selected as the best paper for publication in ACM Transactions on Database Systems. Based on Google Scholar, he has around 3200 citations in his research work.Eleftherios Tiakas received a B.Sc. in Mathematics (1994), a B.Sc. and an M.Sc. in Informatics (2006), and a Ph.D. in Informatics (2011), all the degrees from the Aristotle University of Thessaloniki (AUTH). During the period 2004–2017, he served as Teacher of Mathematics in Secondary Education. From 2011–2017, he served as Adjunct Lecturer with the School of Informatics of AUTH. Since 2017, he has been on the Laboratory Teaching Staff with the School of Informatics of AUTH. His areas of research interest include: Databases, Data Structures, Data Mining, Information Retrieval, Similarity Search, Social Networks, and Bioinformatics. He is the author/co-author of 30 articles published in international journals and conference proceedings, plus 2 book chapters. His publications have received over 600 citations. He participated in 11 research projects and programs funded by the European Union and Greece. Finally, he serves as a PC member and reviewer for several international journals and conferences.Theodoros Tzouramanis is an Assistant Professor in the Department of Computer Science and Biomedical Informatics of the University of Thessaly. He received a five-year Diploma Degree in Electrical and Computer Engineering and a Ph.D. in Informatics, both from the Aristotle University of Thessaloniki. Prior to his current position, he served from 2003–2019 as Lecturer and later as Assistant Professor in the Department of Information and Communication Systems Engineering of the University of the Aegean. He has also been teaching at the Hellenic Open University since 2005. His research interests focus on data management, data security, and privacy. More than50 articles of his work have appeared in refereed scientific journals, conference proceedings, and chapters in books.Nikolaos Georgiadisis a Ph.D. candidate at the School of Informatics of Aristotle University of Thessaloniki (AUTH). He has a B.Sc. in Software Engineering from the Technical University of Kavala and a M.Sc. in Information Systems from the School of Informatics of AUTH. His main research interests focus on efficient algorithmic techniques for Knowledge Discovery from Big Data. He has professional experience as a Software Engineer in the IT industry in various companies in Greece, Germany, and Switzerland for over 15 years.Yannis Manolopoulos is a Professor and Vice-rector of the Open University of Cyprus. He received a five-year Diploma Degree in Electrical Engineering and a Ph.D. in Computer Engineering, both from the Aristotle University of Thessaloniki (AUTH). He has been with the University of Toronto, the University of Maryland at College Park,the University of Cyprus, the Hellenic Open University, and AUTH, where he served as Head of the School of Informatics. He has also served as Rector of the University of Western Macedonia in Greece and Vice-Chair of the Greek Computer Society. His research interest focuses on Data Management. He has co-authored 5 monographs and 11 textbooks in Greek, as well as >300 journal and conference papers. He has received >14,700 citations from >2,200 distinct academic institutions (h-index=57). He has also received 5 best paper awards from SIGMOD, ECML/PKDD, MEDES (2), and ISSPIT conferences and has been invited as keynote speaker at 20 international events. He has served as the main co-organizer of several CORE A/B conferences: SSTD 2003, SSDBM 2004, ADBIS 2006, ICANN 2010, WISE 2013, CAISE 2014, TPDL 2017, DASFAA 2018, IDEAS 2019, WI 2019, and SOFSEM 2020. He has also acted as an evaluator for funding agencies in Austria, Canada, Cyprus, Czech Republic, Estonia, EU, Georgia, Greece,Hong-Kong, Israel, Italy, Lithuania, Poland, and Russia. Currently, he serves on the Editorial Boards of the following journals (among others): Information Systems, World Wide Web, Computer Journal, Data Science and Analytics, and Artificial Intelligence Tools.

• List of Figures.- List of Tables.- Preface.- Acknowledgments.- Introduction.- Skyline Queries.- Variations of Skyline Queries.- Top-??.- Applications of Dominance-Based Queries.- Bibliography.- Authors' Biographies.- Index.

Apostolos N. Papadopoulos is an Associate Professor of Computer Science at the School of Informatics of Aristotle University of Thessaloniki (AUTH). He received his five-year Diploma Degree in Computer Engineering and Informatics from the University of Patras, and his Ph.D. Degree in Informatics from the School of Informatics (AUTH). His research interests include Data Management, Data Mining, and Big Data Analytics. He has served as a track co-chair of ACM SAC DTTA (Database Technologies Techniques and Applications) Track from 2005 until now, as well as a PC member in several International Conferences related to Data Management and Data Mining. He has co-presented four tutorials in ASONAM 2015, EDBT/ICDT 2016, ICDM 2016, and ECML/PKDD 2017 on the “Core Decomposition of Networks.” The paper “SkyGraph: an algorithm for important subgraph discovery in relational graphs,” Proceedings of ECML/PKDD, Antwerp, Belgium, 2008, received the Best Knowledge Discovery Paper Award, whereas the paper“Metric-Based Top-k Dominating Queries,” Proceedings of the 17th International Conference on Extending Database Technology (EDBT), Athens, 2014, was selected as the best paper for publication in ACM Transactions on Database Systems. Based on Google Scholar, he has around 3200 citations in his research work.Eleftherios Tiakas received a B.Sc. in Mathematics (1994), a B.Sc. and an M.Sc. in Informatics (2006), and a Ph.D. in Informatics (2011), all the degrees from the Aristotle University of Thessaloniki (AUTH). During the period 2004–2017, he served as Teacher of Mathematics in Secondary Education. From 2011–2017, he served as Adjunct Lecturer with the School of Informatics of AUTH. Since 2017, he has been on the Laboratory Teaching Staff with the School of Informatics of AUTH. His areas of research interest include: Databases, Data Structures, Data Mining, Information Retrieval, Similarity Search, Social Networks, and Bioinformatics. He is the author/co-author of 30 articles published in international journals and conference proceedings, plus 2 book chapters. His publications have received over 600 citations. He participated in 11 research projects and programs funded by the European Union and Greece. Finally, he serves as a PC member and reviewer for several international journals and conferences.Theodoros Tzouramanis is an Assistant Professor in the Department of Computer Science and Biomedical Informatics of the University of Thessaly. He received a five-year Diploma Degree in Electrical and Computer Engineering and a Ph.D. in Informatics, both from the Aristotle University of Thessaloniki. Prior to his current position, he served from 2003–2019 as Lecturer and later as Assistant Professor in the Department of Information and Communication Systems Engineering of the University of the Aegean. He has also been teaching at the Hellenic Open University since 2005. His research interests focus on data management, data security, and privacy. More than50 articles of his work have appeared in refereed scientific journals, conference proceedings, and chapters in books.Nikolaos Georgiadisis a Ph.D. candidate at the School of Informatics of Aristotle University of Thessaloniki (AUTH). He has a B.Sc. in Software Engineering from the Technical University of Kavala and a M.Sc. in Information Systems from the School of Informatics of AUTH. His main research interests focus on efficient algorithmic techniques for Knowledge Discovery from Big Data. He has professional experience as a Software Engineer in the IT industry in various companies in Greece, Germany, and Switzerland for over 15 years.Yannis Manolopoulos is a Professor and Vice-rector of the Open University of Cyprus. He received a five-year Diploma Degree in Electrical Engineering and a Ph.D. in Computer Engineering, both from the Aristotle University of Thessaloniki (AUTH). He has been with the University of Toronto, the University of Maryland at College Park,the University of Cyprus, the Hellenic Open University, and AUTH, where he served as Head of the School of Informatics. He has also served as Rector of the University of Western Macedonia in Greece and Vice-Chair of the Greek Computer Society. His research interest focuses on Data Management. He has co-authored 5 monographs and 11 textbooks in Greek, as well as >300 journal and conference papers. He has received >14,700 citations from >2,200 distinct academic institutions (h-index=57). He has also received 5 best paper awards from SIGMOD, ECML/PKDD, MEDES (2), and ISSPIT conferences and has been invited as keynote speaker at 20 international events. He has served as the main co-organizer of several CORE A/B conferences: SSTD 2003, SSDBM 2004, ADBIS 2006, ICANN 2010, WISE 2013, CAISE 2014, TPDL 2017, DASFAA 2018, IDEAS 2019, WI 2019, and SOFSEM 2020. He has also acted as an evaluator for funding agencies in Austria, Canada, Cyprus, Czech Republic, Estonia, EU, Georgia, Greece,Hong-Kong, Israel, Italy, Lithuania, Poland, and Russia. Currently, he serves on the Editorial Boards of the following journals (among others): Information Systems, World Wide Web, Computer Journal, Data Science and Analytics, and Artificial Intelligence Tools.

• List of Figures.- List of Tables.- Preface.- Acknowledgments.- Introduction.- Skyline Queries.- Variations of Skyline Queries.- Top-??.- Applications of Dominance-Based Queries.- Bibliography.- Authors' Biographies.- Index.