research

I study data systems. I am particularly interested in social aspects of data systems, query languages, and schema languages.

I am currently investigating data systems education and data engineering challenges in the management of graph data such as social networks, knowledge graphs, biological networks, and communication networks.

selected results

• Threshold queries. Angela Bonifati, Stefania Dumbrava, George Fletcher, Jan Hidders, Matthias Hofer, Wim Martens, Filip Murlak, Joshua Shinavier, Slawek Staworko, Dominik Tomaszuk. SIGMOD Record 2023. ACM SIGMOD Research Highlight Award 2023.
• PG-Schema: Schemas for Property Graphs. Renzo Angles, Angela Bonifati, Stefania Dumbrava, George Fletcher, Alastair Green, Jan Hidders, Bei Li, Leonid Libkin, Victor Marsault, Wim Martens, Filip Murlak, Stefan Plantikow, Ognjen Savkovic, Michael Schmidt, Juan Sequeda, Slawek Staworko, Dominik Tomaszuk, Hannes Voigt, Domagoj Vrgoc, Mingxi Wu, Dusan Zivkovic. SIGMOD 2023. SIGMOD 2023 Best Research Paper Award - Industry Track.
• AvantGraph query processing engine. Wilco van Leeuwen, Thomas Mulder, Bram Van De Wall, George Fletcher, Nikolay Yakovets. VLDB 2022.
• ReLOG: A unified framework for relationship-based access control over graph databases. Stanley Clark, Nikolay Yakovets, George Fletcher, Nicola Zannone. DBSec 2022.
• Language-aware indexing for conjunctive path queries. Yuya Sasaki, George Fletcher, Makoto Onizuka. ICDE 2022.
• Identifying SQL misconceptions of novices: findings from a think-aloud study. Daphne Miedema, Efthimia Aivaloglou, George Fletcher. ICER 2021. ICER 2021 Honorable Mention Award. Discussion on Hacker News.
• SQLVis: Visual query representations for supporting SQL learners. Daphne Miedema and George Fletcher. VL/HCC 2021.
• How fair is fairness-aware representative ranking? Akrati Saxena, George Fletcher, Mykola Pechenizkiy. Data Science for Social Good 2021.
• PG-Keys: Keys for property graphs. Renzo Angles, Angela Bonifati, Stefania Dumbrava, George Fletcher, Keith W. Hare, Jan Hidders, Victor E. Lee, Bei Li, Leonid Libkin, Wim Martens, Filip Murlak, Josh Perryman, Ognjen Savkovic, Michael Schmidt, Juan Sequeda, Sławek Staworko, Dominik Tomaszuk. SIGMOD 2021.
• Combining sampling and synopses with worst-case optimal runtime and quality guarantees for graph pattern cardinality estimation. Kyoungmin Kim, Hyeonji Kim, George Fletcher, Wook-Shin Han. SIGMOD 2021.
• Leveraging temporal and topological selectivities in temporal subgraph query processing. Kaijie Zhu, George Fletcher, Nikolay Yakovets. ICDE 2021.
• GGDs: Graph generating dependencies. Larissa Shimomura, George Fletcher, Nikolay Yakovets. CIKM 2020.
• Towards planning of regular queries with memory. Thomas Mulder, Nikolay Yakovets, George Fletcher. EDBT 2020.
• Scalable temporal clique enumeration. Kaijie Zhu, George Fletcher, Nikolay Yakovets, Odysseas Papapetrou, Yuqing Wu. SSTD 2019.
• An experimental study of context-free path query evaluation methods. Jochem Kuijpers, George Fletcher, Nikolay Yakovets, Tobias Lindaaker. SSDBM 2019.
• Querying Graphs. Angela Bonifati, George Fletcher, Hannes Voigt, Nikolay Yakovets. Morgan & Claypool, 2018.
• Graph Data Management. George Fletcher, Jan Hidders, Josep Lluís Larriba-Pey (Eds.). Springer, 2018.
• G-CORE: A core for future graph query languages. Renzo Angles, Marcelo Arenas, Pablo Barceló, Peter Boncz, George Fletcher, Claudio Gutierrez, Tobias Lindaaker, Marcus Paradies, Stefan Plantikow, Juan Sequeda, Oskar van Rest, Hannes Voigt. SIGMOD 2018. open source code.
• Landmark indexing for evaluation of label-constrained reachability queries. Lucien Valstar, George Fletcher, Yuichi Yoshida. SIGMOD 2017. open source code.
• gMark: schema-driven generation of graphs and queries. Guillaume Bagan, Angela Bonifati, Radu Ciucanu, George Fletcher, Aurélien Lemay, Nicky Advokaat. IEEE Transactions on Knowledge and Data Engineering, 2017. See also our demo at VLDB 2016 and open source code.
• Structural characterizations of the navigational expressiveness of relation algebras on a tree. George Fletcher, Marc Gyssens, Jan Paredaens, Dirk Van Gucht, and Yuqing Wu. J. Comput. Syst. Sci., 2016.
• Relative expressive power of navigational querying on graphs. George Fletcher, Marc Gyssens, Dirk Leinders, Dimitri Surinx, Jan Van den Bussche, Dirk Van Gucht, Stijn Vansummeren, Yuqing Wu. Information Sciences, 2015.
• Similarity and bisimilarity notions appropriate for characterizing indistinguishability in fragments of the calculus of relations. George Fletcher, Marc Gyssens, Dirk Leinders, Jan Van den Bussche, Dirk Van Gucht, Stijn Vansummeren. J. Log. Comput., 2015.
• Efficient and scalable trie-based algorithms for computing set containment relations. Yongming Luo, George Fletcher, Jan Hidders, Paul De Bra. ICDE 2015, Seoul.
• Principles of guarded structural indexing. Francois Picalausa, George Fletcher, Jan Hidders, Stijn Vansummeren. ICDT 2014, Athens, Greece.
• On reflection in linked data management. George Fletcher. DESWeb 2014, Chicago (slides).
• External memory k-bisimulation reduction of big graphs. Yongming Luo, George Fletcher, Jan Hidders, Yuqing Wu, Paul De Bra. CIKM 2013, San Francisco.
• A structural approach to indexing triples. Francois Picalausa, Yongming Luo, George Fletcher, Jan Hidders, Stijn Vansummeren. ESWC 2012, Heraklion.
• Efficient external-memory bisimulation on DAGs. Jelle Hellings, George Fletcher, Herman Haverkort. SIGMOD 2012, Scottsdale (open source code).
• Towards a theory of search queries. George Fletcher, Jan Van den Bussche, Dirk Van Gucht, and Stijn Vansummeren. ACM Transactions on Database Systems, 2010.
• Towards a general framework for effective solutions to the data mapping problem. George Fletcher and Catherine Wyss. Journal on Data Semantics, 2009.
• Thinking about computational thinking. James J. Lu and George Fletcher. SIGCSE 2009, Chattanooga. Edited version also appeared in Communications of the ACM, 2009.
• A methodology for coupling fragments of XPath with structural indexes for XML documents. George Fletcher, Dirk Van Gucht, Yuqing Wu, Marc Gyssens, Sofía Brenes, and Jan Paredaens. Information Systems, 2009.

For more details, you can also check out my entries at DBLP and CSB.

You can find information about students and post-docs I've collaborated with on my teaching & mentoring page. If you are a student interested in a thesis topic in data-intensive systems, please feel free to get in touch.