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Dr. Jelle Hellings

Assistant Professor

Department of Computing and Software

Expertise:
resilient systems (blockchains); high-performance data management; database theory; graph databases

Overview

Currently, my focus is on the development of scalable resilient systems that can manage data and processing complex transactions, while providing strong guarantees toward users in the presence of faulty behavior (e.g., hardware failures, software failures, and malicious attacks). Furthermore, I work on database theory, on semi-structured data with a main focus on graph databases (e.g., graph query languages, constraints on graph data, graph query evaluation algorithms), and on external-memory algorithms for indexing very large graph datasets.

In general, my research is centered around novel directions for high-performance large-scale data management systems. My research has a strong theoretical component (e.g., lower bound results, finite model theory, dependency theory) and a strong algorithmic component (e.g., external-memory algorithms, distributed algorithms, join algorithms).

Previously, I worked as a Postdoc Scholar in the Exploratory Systems Lab at the Computer Science Department of the University of California, Davis, where I worked on scalable resilient distributed data processing. I did my doctoral training in the Databases and Theoretical Computer Science research group at Hasselt University, where I worked on semi-structured data with a main focus on graph databases (e.g., graph query languages, constraints on graph data, graph query evaluation algorithms).

Education

Publications

Recent

Books

  1. MC 2021. Fault-tolerant distributed transactions on blockchain. Suyash Gupta, Jelle Hellings, and Mohammad Sadoghi. (2021). In: Synthesis Lectures on Data Management. Morgan & Claypool. DOI: 10.2200/S01068ED1V01Y202012DTM065.

Journal Papers

  1. JLAMP 2022. The power of Tarski's relation algebra on trees. Jelle Hellings, Yuqing Wu, Marc Gyssens, and Dirk Van Gucht. (2022). In: Journal of Logical and Algebraic Methods in Programming, 126. Elsevier. DOI: 10.1016/j.jlamp.2022.100748. (author copy, project page).
  2. VLDB 2021. ByShard: Sharding in a Byzantine environment. Jelle Hellings and Mohammad Sadoghi. (2021). In: Proceedings of the VLDB Endowment, 14(11), 2230-2243. VLDB. DOI: 10.14778/3476249.3476275. (author copy, slides, poster, project page).
  3. CJ 2020. From relation algebra to semi-join algebra: An approach to graph query optimization. Jelle Hellings, Catherine L. Pilachowski, Dirk Van Gucht, Marc Gyssens, and Yuqing Wu. (2020). In: The Computer Journal, 64(5), 789-811. Oxford University Press. DOI: 10.1093/comjnl/bxaa031. (author copy).
  4. VLDB 2020. ResilientDB: global scale resilient blockchain fabric. Suyash Gupta, Sajjad Rahnama, Jelle Hellings, and Mohammad Sadoghi. (2020). In: Proceedings of the VLDB Endowment, 13(6), 868-883. VLDB. DOI: 10.14778/3380750.3380757. (author copy, technical report, video by Suyash Gupta).
  5. IS 2020. Comparing the expressiveness of downward fragments of the relation algebra with transitive closure on trees. Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van den Bussche, Stijn Vansummeren, and George H. L. Fletcher. (2020). In: Information Systems, 89. Elsevier. DOI: 10.1016/j.is.2019.101467. (author copy, technical report, project page).
  6. AMAI 2019. First-order definable counting-only queries. Jelle Hellings, Marc Gyssens, Dirk Van Gucht, and Yuqing Wu. (2019). In: Annals of Mathematics and Artificial Intelligence, 87, 109-136. Springer. DOI: 10.1007/s10472-019-09652-8. (author copy).
  7. JCSS 2019. Calculi for symmetric queries. Marc Gyssens, Jelle Hellings, Jan Paredaens, Dirk Van Gucht, Jef Wijsen, Yuqing Wu. (2019). In: Journal of Computer and System Sciences, 105, 54-86. Elsevier. DOI: 10.1016/j.jcss.2019.04.003. (author copy).
  8. AMAI 2016. Implication and axiomatization of functional and constant constraints. Jelle Hellings, Marc Gyssens, Jan Paredaens, Yuqing Wu. (2016). In: Annals of Mathematics and Artificial Intelligence, 76(3), 251-279. Springer. DOI: 10.1007/s10472-015-9473-7. (author copy).

Conference Proceedings (peer-reviewed)

  1. FoIKS 2022a. The fault-tolerant cluster-sending problem. Jelle Hellings and Mohammad Sadoghi. (2022). In: Foundations of Information and Knowledge Systems, 168-186. Springer. DOI: 10.1007/978-3-031-11321-5_10. (author copy, slides).
  2. FoIKS 2022b. Optimizing multiset relational algebra queries using weak-equivalent rewrite rules. Jelle Hellings, Yuqing Wu, Dirk Van Gucht, and Marc Gyssens. (2022). In: Foundations of Information and Knowledge Systems, 187-205. Springer. DOI: 10.1007/978-3-031-11321-5_11. (author copy, slides).
  3. EDBT 2021. Proof-of-Execution: Reaching consensus through fault-tolerant speculation. Suyash Gupta, Sajjad Rahnama, Jelle Hellings, and Mohammad Sadoghi. (2021). In: Proceedings of the 24th International Conference on Extending Database Technology (EDBT), 301-312. OpenProceedings.org. DOI: 10.5441/002/edbt.2021.27. (author copy, video by Suyash Gupta).
  4. ICDE 2021. RCC: Resilient concurrent consensus for high-throughput secure transaction processing. Suyash Gupta, Jelle Hellings, and Mohammad Sadoghi. (2021). In: 2021 IEEE 37th International Conference on Data Engineering (ICDE), 1392-1403. IEEE. DOI: 10.1109/ICDE51399.2021.00124. (author copy, video by Suyash Gupta).
  5. TIME 2020. Stab-Forests: Dynamic Data Structures for Efficient Temporal Query Processing. Jelle Hellings and Yuqing Wu. (2020). In: 27th International Symposium on Temporal Representation and Reasoning (TIME 2020), 18:1-18:19. Schloss Dagstuhl. DOI: 10.4230/LIPIcs.TIME.2020.18. (author copy, slides, project page).
  6. LSGDA 2020. Explaining results of path queries on graphs. Jelle Hellings. (2020). In: Software Foundations for Data Interoperability and Large Scale Graph Data Analytics, 84-98. Springer. DOI: 10.1007/978-3-030-61133-0_7. (author copy, technical report, slides, project page).
  7. ICDT 2020. Coordination-free Byzantine replication with minimal communication costs. Jelle Hellings and Mohammad Sadoghi. (2020). In: 23rd International Conference on Database Theory (ICDT 2020), 17:1-17:20. Schloss Dagstuhl. DOI: 10.4230/LIPIcs.ICDT.2020.17. (author copy, slides, video).
  8. DISC 2019a. Brief announcement: The fault-tolerant cluster-sending problem. Jelle Hellings and Mohammad Sadoghi. (2019). In: 33rd International Symposium on Distributed Computing (DISC 2019), 45:1-45:3. Schloss Dagstuhl. DOI: 10.4230/LIPIcs.DISC.2019.45. (author copy, technical report, slides).
  9. DISC 2019b. Brief announcement: Revisiting consensus protocols through wait-free parallelization. Suyash Gupta, Jelle Hellings, and Mohammad Sadoghi. (2019). In: 33rd International Symposium on Distributed Computing (DISC 2019), 44:1-44:3. Schloss Dagstuhl. DOI: 10.4230/LIPIcs.DISC.2019.44. (author copy, technical report, slides).
  10. FoIKS 2018a. The power of tarski's relation algebra on trees. Jelle Hellings, Yuqing Wu, Marc Gyssens, and Dirk Van Gucht. (2018). In: Foundations of Information and Knowledge Systems, 244-264. Springer. DOI: 10.1007/978-3-319-90050-6_14. (author copy, slides, project page).
  11. FoIKS 2018b. First-order definable counting-only queries. Jelle Hellings, Marc Gyssens, Dirk Van Gucht, and Yuqing Wu. (2018). In: Foundations of Information and Knowledge Systems, 225-243. Springer. DOI: 10.1007/978-3-319-90050-6_13. (author copy, slides).
  12. DBPL 2017. From relation algebra to semi-join algebra: An approach for graph query optimization. Jelle Hellings, Catherine L. Pilachowski, Dirk Van Gucht, Marc Gyssens, and Yuqing Wu. (2017). In: Proceedings of The 16th International Symposium on Database Programming Languages, 5:1-5:10. ACM. DOI: 10.1145/3122831.3122833. (author copy, slides).
  13. DBPL 2015. Relative expressive power of downward fragments of navigational query languages on trees and chains. Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van den Bussche, Stijn Vansummeren, and George H. L. Fletcher. (2015). In: Proceedings of the 15th Symposium on Database Programming Languages, 59-68. ACM. DOI: 10.1145/2815072.2815081. (author copy, slides, project page).
  14. ICDT 2014. Conjunctive context-free path queries. Jelle Hellings. (2014). In: Proceedings of the 17th International Conference on Database Theory (ICDT), 119-130. OpenProceedings.org. DOI: 10.5441/002/icdt.2014.15. (author copy, slides).
  15. FoIKS 2014. Implication and axiomatization of functional constraints on patterns with an application to the RDF data model. Jelle Hellings, Marc Gyssens, Jan Paredaens, and Yuqing Wu. (2014). In: Foundations of Information and Knowledge Systems, 250-269. Springer. DOI: 10.1007/978-3-319-04939-7_12. (author copy, slides).
  16. ICDT 2013. Walk logic as a framework for path query languages on graph databases. Jelle Hellings, Bart Kuijpers, Jan Van den Bussche, and Xiaowang Zhang. (2013). In: Proceedings of the 16th International Conference on Database Theory, 117-128. ACM. DOI: 10.1145/2448496.2448512. (author copy, slides).
  17. SIGMOD 2012. Efficient external-memory bisimulation on DAGs. Jelle Hellings, George H.L. Fletcher, and Herman Haverkort. (2012). In: Proceedings of the 2012 ACM SIGMOD International Conference on Management of Data, 553-564. ACM. DOI: 10.1145/2213836.2213899. (author copy, slides, project page).

Tutorials, Demos, and Talks

  1. ConsensusDays 21. Efficient fault-tolerant cluster-sending: Reliable and efficient communication between Byzantine fault-tolerant clusters. Jelle Hellings and Mohammad Sadoghi. (2021). (abstract, slides).
  2. VLDB 2020 Tutorial. Building High Throughput Permissioned Blockchain Fabrics: Challenges and Opportunities. Suyash Gupta, Jelle Hellings, Sajjad Rahnama, and Mohammad Sadoghi. (2020). In: Proceedings of the VLDB Endowment, 13(12), 3441-3444. VLDB. DOI: 10.14778/3415478.3415565. (author copy, slides, video of the entire tutorial).
  3. VLDB 2020 Demo. Scalable, resilient, and configurable permissioned blockchain fabric. Sajjad Rahnama, Suyash Gupta, Thamir M. Qadah, Jelle Hellings, and Mohammad Sadoghi. (2020). In: Proceedings of the VLDB Endowment, 13(12), 2893-2896. VLDB. DOI: 10.14778/3415478.3415502. (author copy, video by Sajjad Rahnama).
  4. DEBS 2020 Tutorial. Blockchain consensus unraveled: Virtues and limitations. Suyash Gupta, Jelle Hellings, Sajjad Rahnama, and Mohammad Sadoghi. (2020). In: Proceedings of the 14th ACM International Conference on Distributed and Event-Based Systems, 218-221. ACM. DOI: 10.1145/3401025.3404099. (author copy, slides, video).
  5. Reimagine 2020. An in-depth look of BFT consensus in blockchain: Challenges and opportunities. Suyash Gupta, Jelle Hellings, Sajjad Rahnama, and Mohammad Sadoghi. (2020). (slides).
  6. FAB 2020. ResilientDB: Global scale resilient blockchain fabric. Suyash Gupta, Sajjad Rahnama, Jelle Hellings and Mohammad Sadoghi. (2020). In: The third International Symposium on Foundations and Applications of Blockchain. (abstract, video by Suyash Gupta).
  7. Middleware 2019. An in-depth look of BFT consensus in blockchain: Challenges and opportunities. Suyash Gupta, Jelle Hellings, Sajjad Rahnama, and Mohammad Sadoghi. (2019). In: Proceedings of the 20th International Middleware Conference--Tutorials, 6-10. ACM. DOI: 10.1145/3366625.3369437. (author copy, slides).
  8. HPTS 2019. Efficient transaction processing in Byzantine fault tolerant environments. Suyash Gupta, Jelle Hellings, Thamir Qadah, Sajjad Rahnama, and Mohammad Sadoghi. (2019). In: 18th International Workshop on High Performance Transaction Systems. (abstract, video by Suyash Gupta).
  9. DBDBD 2016. Graph query optimization using semi-join rewritings. Jelle Hellings. (2016). In: The Dutch-Belgian DataBase Day. (abstract, slides).
  10. WOG 2013. Path querying on graph databases. Jelle Hellings. (2013). In: WOG (Wetenschappelijke Onderzoeksgemeenschap/Scientific Research Network) Meeting. (long abstract, short abstract, slides).
  11. DBDBD 2011. Efficient external-memory bisimulation on DAGs. Jelle Hellings. (2011). In: The Dutch-Belgian DataBase Day. (abstract, slides, project page).

PhD thesis and Master thesis

  1. PhD thesis. On tarski's relation algebra: Querying trees and chains and the semi-join algebra. Jelle Hellings. (2018). Hasselt University and transnational University of Limburg. Adviser: Marc Gyssens. (author copy, thesis, slides, project page).
  2. Master thesis. Bisimulation partitioning and partition maintenance. Jelle Hellings. (2011). Eindhoven University of Technology. Adviser: George H. L. Fletcher. (author copy, thesis, final slides, mid-term slides, poster, project page).