Angela Bonifati is a full professor of computer science at Universite Claude Bernard Lyon 1 and affiliated with the CNRS Liris research lab. She received her Ph.D. from Politecnico di Milano in 2002 and right after she was a postdoctoral researcher at INRIA Roquencourt. Her current research interests are on the interplay of relational and graph-shaped data paradigms, particularly on schema mapping and data exchange, query processing, and learning for these data models. She was Vice Chair of ICDE 2018 for the information extraction, data cleaning, and curation track and Vice Chair of ICDE 2011 for the semi-structured data track. She is Associate Editor of the VLDB Journal, ACM TODS, and Distributed and Parallel Databases. She is a member-at-large of the ICDT council and serving on the program committees of SIGMOD, PODS, PVLDB, ICDE, and EDBT.George Fletcher is an associate professor of computer science at Technische Universiteit Eindhoven where he is chair of the Database Group. Hedefended a Ph.D. at Indiana University Bloomington in 2007. His research interests span query language design and engineering, foundations of databases, and data integration. His current focus is on management of massive graphs such as social networks and linked open data. He was a co-organizer of the EDBT Summer School on Graph Data Management (2015) and is currently a member of the LDBC Graph Query Language Standardization Task Force. His other recent activities include co-organizing an NII Shonan seminar on Graph Database Systems (2018) and serving on the program committees of SIGMOD, VLDB, ISWC, ICDE, EDBT, and IJCAI.Hannes Voigt is a software engineer at Neo4j since June 2018, where he is part of the Query Languages, Standards, and Research team. Before that he was a post-doctoral researcher at the Dresden Database Systems Group, Technische Universitat Dresden and obtained his Ph.D. from the same university in 2014. As a researcher, he worked on various database topicssuch as declarative graph query languages, database evolution and versioning, management of schema-flexible data, and self-adapting indexes. He is member of the LDBC Graph Query Language Standardization Task Force. Other recent activities include co-editing the section on graph analytics in the Encyclopedia of Big Data Technologies, co-presenting a tutorial on graph query processing at EDBT 2017, and serving on the program committees of VLDB, ICDE, and CIKM.Nikolay Yakovets is an assistant professor of computer science at Technische Universiteit Eindhoven. He obtained his Ph.D. from Lassonde School of Engineering at York University in 2017. He worked on various database topics at IBM CAS Canada and Empress Software Canada. His current focus is on design and implementation of core database technologies, management of massive graph data, and efficient processing of queries on graphs. His recent activities include co-presenting a tutorial on graph query processing at EDBT 2017, co-organizing the 2017 edition of the Dutch-Belgian Database Day, and serving on a program committee of ICDE.

• Foreword.- Acknowledgments.- Introduction.- Data Models.- Query Languages.- Constraints.- Query Specification.- Data Structures and Indexes.- Query Processing.- Physical Operators.- Research Challenges.- Bibliography.- Authors' Biographies.

Angela Bonifati is a full professor of computer science at Universite Claude Bernard Lyon 1 and affiliated with the CNRS Liris research lab. She received her Ph.D. from Politecnico di Milano in 2002 and right after she was a postdoctoral researcher at INRIA Roquencourt. Her current research interests are on the interplay of relational and graph-shaped data paradigms, particularly on schema mapping and data exchange, query processing, and learning for these data models. She was Vice Chair of ICDE 2018 for the information extraction, data cleaning, and curation track and Vice Chair of ICDE 2011 for the semi-structured data track. She is Associate Editor of the VLDB Journal, ACM TODS, and Distributed and Parallel Databases. She is a member-at-large of the ICDT council and serving on the program committees of SIGMOD, PODS, PVLDB, ICDE, and EDBT.George Fletcher is an associate professor of computer science at Technische Universiteit Eindhoven where he is chair of the Database Group. Hedefended a Ph.D. at Indiana University Bloomington in 2007. His research interests span query language design and engineering, foundations of databases, and data integration. His current focus is on management of massive graphs such as social networks and linked open data. He was a co-organizer of the EDBT Summer School on Graph Data Management (2015) and is currently a member of the LDBC Graph Query Language Standardization Task Force. His other recent activities include co-organizing an NII Shonan seminar on Graph Database Systems (2018) and serving on the program committees of SIGMOD, VLDB, ISWC, ICDE, EDBT, and IJCAI.Hannes Voigt is a software engineer at Neo4j since June 2018, where he is part of the Query Languages, Standards, and Research team. Before that he was a post-doctoral researcher at the Dresden Database Systems Group, Technische Universitat Dresden and obtained his Ph.D. from the same university in 2014. As a researcher, he worked on various database topicssuch as declarative graph query languages, database evolution and versioning, management of schema-flexible data, and self-adapting indexes. He is member of the LDBC Graph Query Language Standardization Task Force. Other recent activities include co-editing the section on graph analytics in the Encyclopedia of Big Data Technologies, co-presenting a tutorial on graph query processing at EDBT 2017, and serving on the program committees of VLDB, ICDE, and CIKM.Nikolay Yakovets is an assistant professor of computer science at Technische Universiteit Eindhoven. He obtained his Ph.D. from Lassonde School of Engineering at York University in 2017. He worked on various database topics at IBM CAS Canada and Empress Software Canada. His current focus is on design and implementation of core database technologies, management of massive graph data, and efficient processing of queries on graphs. His recent activities include co-presenting a tutorial on graph query processing at EDBT 2017, co-organizing the 2017 edition of the Dutch-Belgian Database Day, and serving on a program committee of ICDE.

• Foreword.- Acknowledgments.- Introduction.- Data Models.- Query Languages.- Constraints.- Query Specification.- Data Structures and Indexes.- Query Processing.- Physical Operators.- Research Challenges.- Bibliography.- Authors' Biographies.

Angela Bonifati is a full professor of computer science at Universite Claude Bernard Lyon 1 and affiliated with the CNRS Liris research lab. She received her Ph.D. from Politecnico di Milano in 2002 and right after she was a postdoctoral researcher at INRIA Roquencourt. Her current research interests are on the interplay of relational and graph-shaped data paradigms, particularly on schema mapping and data exchange, query processing, and learning for these data models. She was Vice Chair of ICDE 2018 for the information extraction, data cleaning, and curation track and Vice Chair of ICDE 2011 for the semi-structured data track. She is Associate Editor of the VLDB Journal, ACM TODS, and Distributed and Parallel Databases. She is a member-at-large of the ICDT council and serving on the program committees of SIGMOD, PODS, PVLDB, ICDE, and EDBT.George Fletcher is an associate professor of computer science at Technische Universiteit Eindhoven where he is chair of the Database Group. Hedefended a Ph.D. at Indiana University Bloomington in 2007. His research interests span query language design and engineering, foundations of databases, and data integration. His current focus is on management of massive graphs such as social networks and linked open data. He was a co-organizer of the EDBT Summer School on Graph Data Management (2015) and is currently a member of the LDBC Graph Query Language Standardization Task Force. His other recent activities include co-organizing an NII Shonan seminar on Graph Database Systems (2018) and serving on the program committees of SIGMOD, VLDB, ISWC, ICDE, EDBT, and IJCAI.Hannes Voigt is a software engineer at Neo4j since June 2018, where he is part of the Query Languages, Standards, and Research team. Before that he was a post-doctoral researcher at the Dresden Database Systems Group, Technische Universitat Dresden and obtained his Ph.D. from the same university in 2014. As a researcher, he worked on various database topicssuch as declarative graph query languages, database evolution and versioning, management of schema-flexible data, and self-adapting indexes. He is member of the LDBC Graph Query Language Standardization Task Force. Other recent activities include co-editing the section on graph analytics in the Encyclopedia of Big Data Technologies, co-presenting a tutorial on graph query processing at EDBT 2017, and serving on the program committees of VLDB, ICDE, and CIKM.Nikolay Yakovets is an assistant professor of computer science at Technische Universiteit Eindhoven. He obtained his Ph.D. from Lassonde School of Engineering at York University in 2017. He worked on various database topics at IBM CAS Canada and Empress Software Canada. His current focus is on design and implementation of core database technologies, management of massive graph data, and efficient processing of queries on graphs. His recent activities include co-presenting a tutorial on graph query processing at EDBT 2017, co-organizing the 2017 edition of the Dutch-Belgian Database Day, and serving on a program committee of ICDE.

• Foreword.- Acknowledgments.- Introduction.- Data Models.- Query Languages.- Constraints.- Query Specification.- Data Structures and Indexes.- Query Processing.- Physical Operators.- Research Challenges.- Bibliography.- Authors' Biographies.