CURRICULUM VITAE

CURRENT OCCUPATION

Professor in the Department of Computer and Information Science, Norwegian University of Science and Technology (NTNU).

EDUCATION

• Norwegian University of Science and Technology, Dr.ing. (corresponding to Ph.D. degree), 2000.
  Title of thesis: Vagabond: The Design and Analysis of a Temporal Object Database Management System
• Norwegian Institute of Technology (now the Norwegian University of Science and Technology), Siv.ing. (corresponding to M.Sc. degree), 1993.
  Title of thesis: A Study of Neurocomputers (in Norwegian)

• Full professor, Database Systems Group, NTNU, 2005-.
• Visiting researcher (12 months), Univ. of Piraeus, Greece, 2023-2024.
• Research Director, Norwegian Center for Research-based AI Innovation (NorwAI), 2020-2023.
• Visiting researcher (12 months), Univ. of Piraeus, Greece, 2018-2019.
• Visiting researcher (12 months), Athens University of Economics and Business (AUEB) and Univ. of Piraeus, Greece, 2013-2014.
• Visiting researcher (12 months), Athens University of Economics and Business (AUEB), Greece, 2008-2009.
• Visiting researcher (10 months), Athens University of Economics and Business (AUEB), Greece, 2004-2005.
• Visiting researcher (6 months), Aalborg University, Denmark, 2003.
• Visiting researcher (6 months), Athens University of Economics and Business (AUEB), Greece, 2002.
• Associate professor, Database Systems Group, NTNU, 2001-2005.
• Post-doctoral researcher (9 months) at INRIA, Rocquencourt, France, 2001.
• Associate professor, Group for Computer Architecture and Design, NTNU, 2000.
• Assistant professor, Group for Computer Architecture and Design, NTNU, 1998-2000.
• Research fellow, supported by a grant from the Research Council of Norway, NTNU,1994-98.
• System administrator in the computer department at the Royal Norwegian Air Force Academy, 1993-94.
• Research assistant, Telematics Group at the Computer Science department, Norwegian Institute of Technology, 1992.

Big Data, distributed and parallel database systems, query processing, temporal information retrieval and text mining.

EXTERNAL GRANTS

As a Principal Investigator/Coordinator/Co-PI):

• Norwegian Research Center for AI Innovation (NorwAI), 26M Euro (Centre for Research-based Innovation, funding from NTNU, Norwegian Research Council, and industry partners), 2020-2028.
• CoupledDB: High-Performance Indexing for Emerging GPU-Coupled Databases, 208K Euro (EU H2020-MSCA), 2017-2019.
• ExiBiDa: Exploring new dimensions in Big Data, funding one PhD student and one postdoc, approx. 1M Euro (Norwegian Research Council), 2015-2019.
• CloudIX: Cloud-based Indexing and Query Processing, 212K Euro (EU FP7 with partial funding from the Norwegian Research Council), 2011-2013.
• COMIDOR: Cooperative Mining of Independent Document Repositories, funding two PhD students and two postdocs, approx. 1.1M Euro (Norwegian Research Council), 2008-2013.
• DASCOSA: Database Support for Computational Science Applications,, funding one PhD student and one postdoc, approx. 400K Euro (Norwegian Research Council), 2007-2012.
• XML/Web databases, funding one postdoc, approx. 125K Euro (Norwegian Research Council), 2002-2005.

• Big Data & Machine Learning, 0.5M Euro per year (funded by DNB), 2018-2023.
• Trondheim Analytica (NTNU Digital Transformation program), 2018-2022.
• MUSED: Multi-Source Event Detection, 7M NOK (NTNU funded), 2017-2025
• LongRec: Records Management over Decades (Consortium led by DNV), approx. 2.1M Euro (partially funded by the Norwegian Research Council), 2007-2011.
• IS_A: Integrated Semantic Access in Situated Operations (PI: Jon Atle Gulla), approx. 400K Euro (Norwegian Research Council), 2007-2010.

• KEYSTONE: Semantic keyword-based search on structured data sources (member of Management Committee), ICT COST Action IC1302, 2013-2017.

Journal Papers

1. Shiva Shadrooh and Kjetil Nørvåg, SMoTeF: Smurf money laundering detection using temporal order and flow analysis, Applied intelligence, Vol. 54, June 2024.
   
   
2. Akrivi Vlackou, Christos Doulkeridis, Joćo B. Rocha-Junior, and Kjetil Nørvåg, Decisive Skyline Queries for Truly Balancing Multiple Criteria, Data and Knowledge Engineering Journal, Vol. 147, September 2023.
   
   
3. Quang-Huy Duong, Heri Ramampiaro, Kjetil Nørvåg, and Thu-Lan Dam, Density Guarantee on Finding Multiple Subgraphs and Subtensors, ACM Transactions on Knowledge Discovery from Data, Vol. 15, No. 5, pages 1-32, May 2021.
   
   
4. Thu-Lan Dam, Sean Chester, Kjetil Nørvåg, and Quang-Huy Duong, Efficient Top-k Recently-Frequent Term Querying over Spatio-Temporal Textual Streams, Information Systems, Vol. 97, March 2021.
   
   
5. Youcef Djenouri, Jerry Chun-Wei Lin, Kjetil Nørvåg, Heri Ramampiaro, Philip S. Yu, Exploring Decomposition for Solving Pattern Mining Problems, ACM Transactions on Management Information Systems, Vol. 12, No. 2, February 2021.
   
   
6. Youcef Djenouri, Asma Belhadi, Kjetil Nørvåg, Heri Ramampiaro, Florent Masseglia, and Jerry Chun-Wei Lin, Space Time Series Clustering: Algorithms, Taxonomy, and Case Study on Urban Smart Cities, Engineering Applications of Artificial Intelligence, Vol. 95, Article 103857, October 2020.
   
   
7. Özer Özdikis, Heri Ramampiaro, and Kjetil Nørvåg Locality-Adapted Kernel Densities of Term Co-occurrences for Location Prediction of Tweets, Information Processing & Management, Vol. 56, No. 4, pages 1280-1299, 2019.
   
   
8. Christoph Trattner, Tomasz Kusmierczyk, and Kjetil Nørvåg, Investigating and Predicting Online Food Recipe Upload Behavior, Information Processing & Management, Vol. 56, No. 3, pages 654-673, 2019.
   
   
9. Lan Thu Dam, Heri Ramampiaro, Kjetil Nørvåg, and Quang-Huy Duong, Towards Efficiently Mining Closed High Utility Itemsets from Incremental Databases, Knowledge-Based Systems, Vol. 165, pages 13-29, 2019.
   
   
10. Quang-Huy Duong, Heri Ramampiaro, and Kjetil Nørvåg, Applying Temporal Dependence to Detect Changes in Streaming Data, Applied intelligence, Vol. 48, No. 12, pages 4805-4823, 2018.
    
    
11. Quang-Huy Duong, Heri Ramampiaro, Kjetil Nørvåg, Philippe Fournier-Viger, and Thu-Lan Dam, High Utility Drift Detection in Quantitative Data Streams, Knowledge-Based Systems, Vol. 157, pages 34-51, 2018.
    
    
12. Quang-Huy Duong, Philippe Fournier-Viger, Heri Ramampiaro, Kjetil Nørvåg, and Thu-Lan Dam, Efficient high utility itemset mining using buffered utility-lists, Applied Intelligence, Vol. 48, No. 7, pages 1859-1877, 2018.
    
    
13. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Exploratory product search using top-k join queries, Information Systems, Vol. 64, March, pages 75-92, 2017.
    
    
14. Christos Doulkeridis and Kjetil Nørvåg, A Survey of Large-Scale Analytical Query Processing in MapReduce, VLDB Journal, Vol. 23, No. 3, pages 355-380, June 2014.
    
    
15. Kostas Stefanidis, Eirini Ntoutsi, Mihalis Petropoulos, Kjetil Nørvåg, and Hans-Peter Kriegel, A Framework for Modeling, Computing and Presenting Time-aware Recommendations, Transactions on Large-Scale Data- and Knowledge-Centered Systems, Vol. 10, pages 146-172, 2013.
    
    
16. Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Distributed Top-k Query Processing by Exploiting Skyline Summaries, Distributed and Parallel Databases, Vol. 30, No. 3, August 2012.
    
    
17. Akrivi Vlachou, Christos Doulkeridis, Yannis Kotidis, and Kjetil Nørvåg, Monochromatic and Bichromatic Reverse Top-k Queries, IEEE Transactions on Knowledge and Data Engineering, Vol. 23, No. 8, August 2011.
    
    
18. Robert Neumayer, Christos Doulkeridis, and Kjetil Nørvåg, Hybrid Approach for Estimating Document Frequencies in Unstructured P2P Networks, Information Systems, Vol. 36, No. 3, May 2011.
    
    
19. Jon Olav Hauglid, Norvald H. Ryeng, and Kjetil Nørvåg, DYFRAM: Dynamic Fragmentation and Replica Management in Distributed Database Systems, Distributed and Parallel Databases, Vol. 23, No. 2-3, December 2010.
    
    
20. Christos Doulkeridis, Akrivi Vlachou, Kjetil Nørvåg, Yannis Kotidis, and Michalis Vazirgiannis, Efficient Search based on Content Similarity over Self-Organizing P2P Networks, Journal on Peer-to-Peer Networking and Applications, Vol 3, No. 1, pages 67-79, March 2010.
    
    
21. Kjetil Nørvåg, Eirik Eide, and Odin Standal, Query Planning in the PORDaS P2P Database System, JDIM, Vol 6, No. 4, pages 307-314, August 2008.
    
    
22. Christos Doulkeridis, Vassilis Zafeiris, Kjetil Nørvåg, Michalis Vazirgiannis, and Emmanouel Giakoumakis, Context-based Caching and Routing for P2P Web Service Discovery, Distributed and Parallel Databases, Vol 21, No. 1 pages 59-84, Springer Science, February 2007.
    
    
23. Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, DESENT: Decentralized and distributed semantic overlay generation in P2P networks, IEEE Journal on Selected Areas in Communications, Vol. 25, No. 1, pages 25-34, IEEE January 2007.
    
    
24. Kjetil Nørvåg, Granularity Reduction in Temporal Document Databases. Information Systems, Vol 31, No. 2, pages 134-147, Elsevier Science, April 2006.
    
    
25. Kjetil Nørvåg, The Design, Implementation, and Performance of the V2 Temporal Document Database System, Journal of Information and Software Technology, Vol. 46, No. 9, pages 557-574, Elsevier Science, July 2004.
    
    
26. Kjetil Nørvåg, The Vagabond Approach to Logging and Recovery in Transaction-Time Temporal Object Database Systems, IEEE Transactions on Knowledge and Data Engineering, Vol. 16, No. 4, pages 504-518, IEEE, April 2004.
    
    
27. Kjetil Nørvåg, Buffer Performance Modeling In the Context of Unclustered Index Accesses with Non-Uniform Access Pattern, Information Sciences, Vol. 167, No. 1-4, pages 239-262, Elsevier Science, December 2004.
    
    
28. Kjetil Nørvåg, Supporting Temporal Text-Containment Queries in Temporal Document Databases, Data and Knowledge Engineering Journal, Vol. 49, No. 1, pages 105-125, Elsevier Science, April 2004.
    
    
29. Kjetil Nørvåg, A Study of Object Declustering Strategies in Parallel Temporal Object Database Systems, Information Sciences, Vol. 146, No. 1-4, pages 1-27, Elsevier Science, October 2002.
    
    
30. Kjetil Nørvåg, Signature Caching in Parallel Object Database Systems, Journal of Information and Software Technology, Vol. 44, No. 6, pages 331-341, Elsevier Science, April 2002.
    
    
31. Kjetil Nørvåg, Fine-Granularity Signature Caching in Object Database Systems, Data and Knowledge Engineering Journal, Vol. 38, No. 2, pages 101-119, Elsevier Science, August 2001.
    
    
32. Kjetil Nørvåg, Issues in Transaction-Time Temporal Object Database Systems, Journal of Database Management, Vol. 12, No. 4, pages 40-51, Oct-Dec 2001.
    
    

Books

33. Nattiya Kanhabua, Roi Blanco, and Kjetil Nørvåg, Temporal Information Retrieval, Foundations and Trends in Information Retrieval, Now Publishers, Vol. 9, No. 2 (2015) pages 91-208, 2015.
    
    
34. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Yannis Kotidis, Peer-to-Peer Query Processing over Multidimensional Data, Springer, 2012.
    
    

Book Chapters

35. Jon Olav Hauglid, Norvald H. Ryeng, and Kjetil Nørvåg, The DASCOSA-DB Grid Database System, Grid and Cloud Database Management (Springer), August 2011.
    
    
36. Christos Doulkeridis, Akrivi Vlachou, Kjetil Nørvåg, and Michalis Vazirgiannis, Distributed semantic overlay networks, Handbook of Peer-to-Peer Networking, Springer, January 2010.
    
    
37. Kjetil Nørvåg, Query Operators in Temporal XML Databases, in L. C. Rivero, J. H. Doorn, V. E. Ferraggine (Eds.), Encyclopedia of Database Technologies and Applications, 2005.
    
    
38. Kjetil Nørvåg and Kjell Bratbergsengen, Optimal Object Descriptor Caching in Temporal Object Database Systems, In K. Tanaka , S. Ghandeharizadeh, and Y. Kambayashi (Eds.), Information Organization and Databases, pages 235-248, Kluwer Academic Publishers, November 2000.
    
    

Edited Conference Proceedings

39. Silvia Chiusano, Tania Cerquitelli, Robert Wrembel, Kjetil Nørvåg, Barbara Catania, Genoveva Vargas-Solar, and Ester Zumpano, New Trends in Database and Information Systems - ADBIS 2022 Short Papers, Doctoral Consortium and Workshops: DOING, K-GALS, MADEISD, MegaData, SWODCH, Turin, Italy, September 5-8, 2022, Proceedings, Springer 2022.
    
    
40. Matthias Hagen, Suzan Verberne, Craig Macdonald, Christin Seifert, Krisztian Balog, Kjetil Nørvåg, Vinay Setty, Advances in Information Retrieval - 44th European Conference on IR Research, ECIR 2022, Stavanger, Norway, April 10-14, 2022, Proceedings, Springer 2022
    
    
41. Walid G. Aref, Michela Bertolotto, Panagiotis Bouros, Christian S. Jensen, Ahmed Mahmood, Kjetil Nørvåg, Dimitris Sacharidis, and Mohamed Sarwat, Proceedings of the 16th International Symposium on Spatial and Temporal Databases, SSTD 2019, Vienna, Austria, August 19-21, 2019, ACM 2019.
    
    
42. Natasha Alechina, Kjetil Nørvåg, and Wojciech Penczek, 25th International Symposium on Temporal Representation and Reasoning, TIME 2018, Warsaw, Poland, October 15-17, 2018, LIPIcs 120, Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik 2018.
    
    
43. Marite Kirikova, Kjetil Nørvåg, and George A. Papadopoulos, Advances in Databases and Information Systems - 21st European Conference, ADBIS 2017, Lecture Notes in Computer Science 10509, Springer 2017.
    
    
44. Marite Kirikova, Kjetil Nørvåg, George A. Papadopoulos, Johann Gamper, Robert Wrembel, Jerome Darmont, and Stefano Rizzi, New Trends in Databases and Information Systems - ADBIS 2017 Short Papers and Workshops, AMSD, BigNovelTI, DAS, SW4CH, DC, Communications in Computer and Information Science 767, Springer 2017.
    
    
45. Chee Yong Chan, Jiaheng Lu, Kjetil Nørvåg, and Egemen Tanin, Workshops Proceedings of the 29th IEEE International Conference on Data Engineering, ICDE 2013, Brisbane, Australia, April 8-12, 2013. IEEE Computer Society, 2013.
    
    

International Conferences

46. George S. Theodoropoulos, Kjetil Nørvåg, and Christos Doulkeridis, Efficient Semantic Similarity Search over Spatio-textual Data, Proceedings of EDBT'2024, Paestum, Italy, March 2024.
    
    
47. Hassan Abedi Firouzjaei, Dhruv Gupta, and Kjetil Nørvåg, Diversification of Top-k Geosocial Queries, Proceedings of ADBIS'2023, Barcelona, Spain, September 2023.
    
    
48. Akrivi Vlachou, Christos Doulkeridis, Joćo B. Rocha-Junior, and Kjetil Nørvåg, On Decisive Skyline Queries, Proceedings of DaWaK'2022, Vienna, Austria, August 2022.
    
    
49. Akrivi Vlachou, Christos Doulkeridis, Nikolaos Koutroumanis, Dimitrios Poulopoulos, and Kjetil Nørvåg, The SPADES Framework for Scalable Management of Spatio-textual Data, Proceedings of PCI'2020, Athens, Greece, November 2020.
    
    
50. Stella Maropaki, Sean Chester, Christos Doulkeridis, and Kjetil Nørvåg, Diversifying Top-k Point-of-Interest Queries via Collective Social Reach, Proceedings of CIKM'20, Virtual Event, Ireland, October 2020.
    
    
51. Youcef Djenouri, Kjetil Nørvåg, Heri Ramampiaro, and Jerry Chun-Wei Li, Fast and Accurate Group Outlier Detection for Trajectory Data, Proceedings of ADBIS'2020, Lyon, France, August 2020.
    
    
52. Quang-Huy Duong, Heri Ramampiaro, and Kjetil Nørvåg, Multiple Dense Subtensor Estimation with High Density Guarantee, Proceedings of ICDE'2020, Dallas, Texas, USA, April 2020.
    
    
53. Quang-Huy Duong, Heri Ramampiaro, and Kjetil Nørvåg, Sketching Streaming Histogram Elements using Multiple Weighted Factors, Proceedings of CIKM'2019, Beijing, China, November 2019.
    
    
54. Youcef Djenouri, Jerry Chun-Wei Lin, Kjetil Nørvåg, and Heri Ramampiaro, Highly Efficient Pattern Mining Based on Transaction Decomposition, Proceedings of ICDE'2019, Macau SAR, China, April 2019.
    
    
55. Özer Özdikis, Heri Ramampiaro, and Kjetil Nørvåg, Locality-adapted Kernel Densities for Tweet Localization, Proceedings of SIGIR'2018, Ann Arbor, USA, July 2018.
    
    
56. Özer Özdikis, Heri Ramampiaro, and Kjetil Nørvåg, Spatial Statistics of Term Co-occurrences for Location Prediction of Tweets, Proceedings of ECIR'2018, Grenoble, France, March 2018.
    
    
57. Tomasz Kusmierczyk and Kjetil Nørvåg, On Validation and Predictability of Digital Badges' Influence on Individual Users, Proceeedings of AAAI'2018, New Orleans, USA, February 2018.
    
    
58. Jan R. Benetka, Krisztian Balog, and Kjetil Nørvåg, Towards Building a Knowledge Base of Monetary Transactions from a News Collection, Proceedings of JCDL'2017, Toronto, Canada, June 2017.
    
    
59. Jan R. Benetka, Krisztian Balog, and Kjetil Nørvåg, Anticipating Information Needs Based on Check-in Activity, Proceedings of WSDM'2017, Cambridge, UK, February 2017.
    
    
60. Mei Saouk, Christos Doulkeridis, Akrivi Vlachou, and Kjetil Nørvåg, Efficient Processing of Top-k Joins in MapReduce, Proceedings of IEEE BigData 2016, Washington D.C.,USA, December 2016.
    
    
61. Tomasz Kusmierczyk and Kjetil Nørvåg, Online Food Recipe Title Semantics: Combining Nutrient Facts and Topics, Proceeedings of CIKM'2016, Indianapolis, USA, October 2016.
    
    
62. Tomasz Kusmierczyk, Christoph Trattner, and Kjetil Nørvåg, Understanding and Predicting Online Food Recipe Production Patterns, Proceeedings of Hypertext'2016, Halifax, Canada, July 2016.
    
    
63. Sean Chester, Orestis Gkorgkas, and Kjetil Nørvåg, Top-k Dominating Queries, in Parallel, in Memory, Proceedings of EDBT'2016, Bordeaux, France, March 2016.
    
    
64. Santiago Larrain, Christoph Trattner, Denis Parra, Eduardo Graells-Garrido, and Kjetil Nørvåg, Good Times Bad Times: A Study on Recency Effects in Collaborative Filtering for Social Tagging, Proceedings of the 9th ACM Conference on Recommender Systems (RecSys 2015), Vienna, Austria, September 2015.
    
    
65. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Maximizing Influence of Spatio-Textual Objects Based on Keyword Selection, Proceedings of SSTD'2015, Seoul, South Korea, August 2015.
    
    
66. Tomasz Kusmierczyk, Christoph Trattner, and Kjetil Nørvåg, Temporality in Online Food Recipe Consumption and Production (poster), Proceedings of WWW'2015, Firenze, Italy, May 2015.
    
    
67. Tomasz Kusmierczyk, Christoph Trattner, and Kjetil Nørvåg, Temporal Patterns in Online Food Innovation, Proceedings of TempWeb'2015 (WWW Companion Volume), Firenze, Italy, May 2015.
    
    
68. Tomasz Kusmierczyk and Kjetil Nørvåg, Mining Correlations on Massive Bursty Time Series Collections, Proceedings of DASFAA'2015, Hanoi, Vietnam, April 2015.
    
    
69. Jan Rybak, Krisztian Balog, and Kjetil Nørvåg, IR Game: How well do you know information retrieval papers?, Proceedings of GamifIR'15 (co-located with ECIR'2015), Vienna, Austria, March 2015.
    
    
70. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Finding the Most Diverse Products using Preference Queries, Proceedings of EDBT'2015, Brussels, Belgium, March 2015.
    
    
71. Dimitrios Kotsakos, Theodoros Lappas, Dimitrios Kotzias, Dimitrios Gunopulos, Nattiya Kanhabua, and Kjetil Nørvåg, A Burstiness-aware Approach for Document Dating, Proceedings of SIGIR'2014, Gold Coast, Australia, July 2014.
    
    
72. Jan Rybak, Krisztian Balog, and Kjetil Nørvåg, ExperTime: Tracking Expertise over Time (demo), Proceedings of SIGIR'2014, Gold Coast, Australia, July 2014.
    
    
73. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Efficient Processing of Exploratory Top-k Joins, Proceedings of SSDBM'2014, Aalborg, Denmark, July 2014.
    
    
74. Stian Liknes, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, APSkyline: Improved Skyline Computation for Multicore Architectures, Proceedings of DASFAA'2014, Bali, Indonesia, April 2014.
    
    
75. Jan Rybak, Krisztian Balog, and Kjetil Nørvåg, Temporal Expertise Profiling, Proceedings of ECIR'2014, Amsterdam, The Netherlands, April 2014.
    
    
76. Orestis Gkorgkas, Kostas Stefanidis, and Kjetil Nørvåg, A Framework for Grouping and Summarizing Keyword Search Results, Proceedings of ADBIS'2013, Genova, Italy, September 2013.
    
    
77. Marek Ciglan, Michal Laclavik, and Kjetil Nørvåg, On Community Detection in Real-World Networks and the Importance of Degree Assortativity, Proceedings of KDD'2013, Chicago, USA, August 2013.
    
    
78. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Discovering Influential Data Objects over Time, Proceedings of SSTD'2013, Munich, Germany, August 2013.
    
    
79. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Yannis Kotidis, Branch-and-Bound Algorithm for Reverse Top-k Queries, Proceedings of SIGMOD'2013, New York, USA, June 2013.
    
    
80. Krisztian Balog, Naimdjon Takhirov, Heri Ramampiaro, and Kjetil Nørvåg, Multi-step Classification Approaches to Cumulative Citation Recommendation, Proceedings of Open research Areas in Information Retrieval (OAIR'2013), Lisbon, Portugal, May 2013.
    
    
81. Krisztian Balog, Heri Ramampiaro, and Kjetil Nørvåg, KBAAA: A Web-based Toolkit for the Assessment and Analysis of Knowledge Base Acceleration Systems (demo paper), Proceedings of Open research Areas in Information Retrieval (OAIR'2013), Lisbon, Portugal, May 2013.
    
    
82. George Tsatsaronis, Iraklis Varlamis, Nattiya Kanhabua, and Kjetil Nørvåg, Temporal Classifiers for Predicting the Expansion of Medical Subject Headings, Proceedings of CICLing'2013, Samos, Greece, March 2013.
    
    
83. Eivind Bjørkelund, Thomas H. Burnett, and Kjetil Nørvåg, A Study of Opinion Mining and Visualization of Hotel Reviews, Proceedings of iiWAS'2012, Bali, Indonesia, December 2012.
    
    
84. George Tsatsaronis, Iraklis Varlamis, and Kjetil Nørvåg, SemaFor: Semantic Document Indexing using Semantic Forests, Proceedings of CIKM'2012, Maui, Hawaii, USA, October 2012.
    
    
85. Nattiya Kanhabua and Kjetil Nørvåg, Learning to Rank Search Results for Time-Sensitive Queries (poster), Proceedings of CIKM'2012, Maui, Hawaii, USA, October 2012.
    
    
86. Nattiya Kanhabua and Kjetil Nørvåg, Estimating Query Difficulty for News Prediction Retrieval (poster), Proceedings of CIKM'2012, Maui, Hawaii, USA, October 2012.
    
    
87. Krisztian Balog and Kjetil Nørvåg, On the Use of Semantic Knowledge Bases for Temporally-aware Entity Retrieval, Proceedings of ESAIR'2012 (co-located with CIKM'2012), Maui, Hawaii, USA, October 2012.
    
    
88. Krisztian Balog, Robert Neumayer, and Kjetil Nørvåg, Collection Ranking and Selection for Federated Entity Search, Proceedings of SPIRE'2012, Cartagena, Colombia, October 2012.
    
    
89. Irini Ntoutsi, Kostas Stefanidis, Kjetil Nørvåg, and Hans-Peter Kriegel, Fast Group Recommendations by Applying User Clustering, Proceedings of ER'2012, Firenze, Italy, October 2012.
    
    
90. Kostas Stefanidis, Nafiseh Shabib, Kjetil Nørvåg, and John Krogstie, Contextual Recommendations for Groups, Proceedings of NoCoDA 2012 (co-located with ER'2012), Firenze, Italy, October 2012.
    
    
91. Kostas Stefanidis, Irini Ntoutsi, Kjetil Nørvåg, and Hans-Peter Kriegel, A Framework for Time-aware Recommendations, Proceedings of DEXA'2012, Vienna, Austria, September 2012.
    
    
92. Robert Neumayer, Krisztian Balog and Kjetil, Nørvåg, Ranking Distributed Knowledge Repositories, Proceedings of TPDL'2012, Paphos, Cyprus, September 2012.
    
    
93. Christos Doulkeridis and Kjetil Nørvåg, On Saying "Enough Already!" in MapReduce, Proceedings of 1st International Workshop on Cloud Intelligence (Cloud-I 2012, co-located with VLDB'2012), Istanbul, Turkey, August 2012.
    
    
94. Nattiya Kanhabua, Klaus Berberich, and Kjetil Nørvåg, Learning to Select a Time-aware Ranking Model (poster), Proceedings of SIGIR'2012, Portland, Oregon, USA, August 2012.
    
    
95. Marek Ciglan, Kjetil Nørvåg and Ladislav Hluchy, The SemSets Model for Ad-hoc Semantic List Search, Proceedings of WWW'2012, Lyon, France, April 2012.
    
    
96. Christos Doulkeridis, Akrivi Vlachou, Kjetil Nørvåg, Yannis Kotidis, and Neoklis Polyzotis, Processing of Rank Joins in Highly Distributed Systems, Proceedings of ICDE'2012, Washington, DC USA, April 2012.
    
    
97. Robert Neumayer, Krisztian Balog, and Kjetil Nørvåg, On the Modeling of Entities for Ad-hoc Entity Search in the Web of Data, Proceedings of ECIR'2012, Barcelona, Spain, April 2012.
    
    
98. Robert Neumayer, Krisztian Balog, and Kjetil Nørvåg, When Simple is (more than) Good Enough: Effective Semantic Search with (almost) no Semantics (poster), Proceedings of ECIR'2012, Barcelona, Spain, April 2012.
    
    
99. Irene Ntoutsi, Kostas Stefanidis, Kjetil Nørvåg, and Hans-Peter Kriegel, gRecs: A Group Recommendation System based on User Clustering (demo paper), Proceedings of DASFAA'2012, Busan, South Korea, April 2012.
    
    
100. João Batista da Rocha Junior and Kjetil Nørvåg, Top-k Spatial Keyword Queries on Road Networks, Proceedings of EDBT'2012, Berlin, Germany, March 2012.
     
     
101. George Tsatsaronis, Matthias Reimann, Iraklis Varlamis, Orestis Gkorgkas, Kjetil Nørvåg, Efficient Community Detection Using Power Graph Analysis, Proceedings of the 9th International Workshop on Large-Scale and Distributed Systems for Information Retrieval (LSDS-IR'11, in conjunction with CIKM'2011), Glasgow, Scotland, UK, October 2011.
     
     
102. João Batista da Rocha Junior, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Efficient Processing of Top-k Spatial Preference Queries, Proceedings of the VLDB Endowment (PVLDB), Vol. 4, No. 2, September 2011.
     
     
103. George Tsatsaronis, Iraklis Varlamis, Sunna Torge, Matthias Reimann, Kjetil Nørvåg, Michael Schroeder, and Matthias Zschunke, How to Become a Group Leader? or Modelling Author Types based on Graph Mining, Proceedings of TPDL'2011, Berlin, Germany, September 2011.
     
     
104. Robert Neumayer, George Tsatsaronis, and Kjetil Nørvåg, TRUMIT: A Tool to Support Large-Scale Mining of Text Association Rules (demo paper), Proceedings of ECML PKDD'2011, Athens, Greece, September 2011.
     
     
105. João Batista da Rocha Junior, Orestis Gkorgkas, Simon Jonassen, and Kjetil Nørvåg, Efficient Processing of Top-k Spatial Keyword Queries, Proceedings of SSTD'2011, Minneapolis, USA, August 2011.
     
     
106. Nattiya Kanhabua and Kjetil Nørvåg, A Comparison of Temporal Ranking Methods (poster), Proceedings of SIGIR'2011, Beijing, China, July 2011.
     
     
107. Nattiya Kanhabua and Kjetil Nørvåg, Time-based Query Performance Predictors (poster), Proceedings of SIGIR'2011, Beijing, China, July 2011.
     
     
108. Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Monitoring Reverse Top-k Queries Over Mobile Devices, Proceedings of MobiDE'2011, Athens, Greece, June 2011.
     
     
109. Robert Neumayer and Kjetil Nørvåg, Evaluation of Feature Combination Approaches for Text Categorisation, Proceedings of ISMIS'2011, Warsaw, Poland, June 2011.
     
     
110. Norvald H. Ryeng, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Efficient Distributed Top-k Query Processing with Caching, Proceedings of DASFAA'2011, Hong Kong,China, April 2011.
     
     
111. Robert Neumayer, Rudolf Mayer, and Kjetil Nørvåg, Combination of Feature Selection Methods for Text Categorisation, Proceedings of ECIR'2011, Dublin, Ireland, April 2011.
     
     
112. Krisztian Balog, Marek Ciglan, Robert Neumayer, Wei Wei, and Kjetil Nørvåg, NTNU at SemSearch 2011, 4th International Semantic Search Workshop (SEMSEARCH'11), WWW 2011 conference, April 2011.
     
     
113. João Batista da Rocha Junior, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, Efficient Execution Plans for Distributed Skyline Query Processing, Proceedings of EDBT'2011, Uppsala, Sweden, March 2011.
     
     
114. Norvald H. Ryeng, Jon Olav Hauglid, and Kjetil Nørvåg, Site-Autonomous Distributed Semantic Caching, Proceedings of ACM SAC'2011, Taichung, Taiwan, March 2011.
     
     
115. Xiangliang Zhang, Wei Wang, Kjetil Nørvåg, and Michele Sebag, K-AP: Generating Specified K Clusters by Efficient Affinity Propagation, Proceedings of IEEE International Conference on Data Mining (ICDM'2010), Sydney, Australia, December 2010.
     
     
116. Marek Ciglan and Kjetil Nørvåg, Fast detection of size-constrained communities in large networks, Proceedings of WISE'2010, Hong Kong, China, December 2010.
     
     
117. Christos Doulkeridis, Akrivi Vlachou, Kjetil Nørvåg, Yannis Kotidis, and Michalis Vazirgiannis, On the Selectivity of Multidimensional Routing Indices, Proceedings of CIKM'2010, Toronto, Canada, October 2010.
     
     
118. Marek Ciglan and Kjetil Nørvåg, WikiPop - Personalized Event Detection System Based on Wikipedia Page View Statistics (demo paper), Proceedings of CIKM'2010, Toronto, Canada, October 2010.
     
     
119. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Yannis Kotidis, Identifying the Most Influential Data Objects with Reverse Top-k Queries, Proceedings of VLDB'2010, Singapore, September 2010.
     
     
120. Nattiya Kanhabua and Kjetil Nørvåg, Determining Time of Queries for Re-ranking Search Results, Proceedings of ECDL'2010, Glasgow, Scotland, UK, September 2010.
     
     
121. Nattiya Kanhabua and Kjetil Nørvåg, QUEST: Query Expansion using Synonyms over Time (demo paper), Proceedings of ECML PKDD'2010, Barcelona, Spain September 2010.
     
     
122. George Tsatsaronis, Iraklis Varlamis, and Kjetil Nørvåg, SemanticRank: Ranking Keywords and Sentences Using Semantic Graphs, Proceedings of COLING'2010, Beijing, China, August 2010.
     
     
123. Nattiya Kanhabua and Kjetil Nørvåg, Exploiting Time-based Synonyms in Searching Document Archives, Proceedings of JCDL'2010, Brisbane, Australia, June 2010.
     
     
124. Christian Bøhn and Kjetil Nørvåg, Extracting Named Entities and Synonyms from Wikipedia, Proceedings of the 24th IEEE International Conference on Advanced Information Networking and Applications (AINA'2010), Perth, Australia, May 2010.
     
     
125. Marek Ciglan, Etienne Rivière, and Kjetil Nørvåg, Learning to find interesting connections in Wikipedia, Proceedings of the 12th International Asia-Pacific Web Conference (APWeb'2010), Busan, Korea, April 2010.
     
     
126. Marek Ciglan and Kjetil Nørvåg, SGDB - Simple graph database optimized for activation spreading computation, Proceedings of GDM'2010 (in conjunction with DASFAA'2010), Tsukuba, Japan, April 2010.
     
     
127. Akrivi Vlachou, Christos Doulkeridis, Yannis Kotidis, and Kjetil Nørvåg, Reverse Top-k Queries, Proceedings of ICDE'2010, Los Angeles, USA, March 2010.
     
     
128. George Tsatsaronis, Iraklis Varlamis, and Kjetil Nørvåg, An Experimental Study on Unsupervised Graph-based Word Sense Disambiguation, Proceedings of CICLing'2010, Iasi, Romania, March 2010.
     
     
129. Christos Doulkeridis, Akrivi Vlachou, Kjetil Nørvåg, Yannis Kotidis, and Michalis Vazirgiannis, Multidimensional Routing Indices for Efficient Distributed Query Processing, Proceedings of CIKM'2009, Hong Kong, China, November 2009.
     
     
130. George Tsatsaronis, Iraklis Varlamis, Sofia Stamou, Kjetil Nørvåg, and Michalis Vazirgiannis, Semantic Relatedness Hits Bibliographic Data, Proceedings of 11th ACM International Workshop on Web Information and Data Management (WIDM), Hong Kong, China, November 2009.
     
     
131. Robert Neumayer, Christos Doulkeridis, and Kjetil Nørvåg, Aggregation of Document Frequencies in Unstructured P2P Networks, Proceedings of WISE'2009, Poznan, Poland, October 2009.
     
     
132. João Batista da Rocha Junior, Akrivi Vlachou, Christos Doulkeridis, and Kjetil Nørvåg, AGiDS: A Grid-based Strategy for Distributed Skyline Query Processing, Proceedings of Globe'2009, Linz, Austria, September 2009.
     
     
133. Nattiya Kanhabua and Kjetil Nørvåg, Using Temporal Language Models for Document Dating (demo paper), Proceedings of ECML PKDD'2009, Bled, Slovenia, September 2009.
     
     
134. George Tsatsaronis, Iraklis Varlamis, Michalis Vazirgiannis, and Kjetil Nørvåg, Omiotis: A Thesaurus-based Measure of Text Relatedness (demo paper), Proceedings of ECML PKDD'2009, Bled, Slovenia, September 2009.
     
     
135. Akrivi Vlachou and Kjetil Nørvåg, Bandwidth-constrained Distributed Skyline Computation, Proceedings of the 8th International ACM Workshop on Data Engineering for Wireless and Mobile Access (ACM MobiDE'2009, in conjunction with SIGMOD'2009), Providence, USA, June 2009.
     
     
136. Jon Olav Hauglid, Kjetil Nørvåg, and Norvald H. Ryeng, Efficient and Robust Database Support for Data-Intensive Applications in Dynamic Environments, Proceedings of ICDE'2009, Shanghai, China April 2009.
     
     
137. Kjetil Nørvåg and Ole Kristian Fivelstad, Semantic-Based Temporal Text-Rule Mining, Proceedings of the 10th International Conference on Intelligent Text Processing and Computational Linguistics (CICLing 2009), Mexico City, Mexico, March 2009.
     
     
138. Jon Olav Hauglid and Kjetil Nørvåg, PROQID: Partial restarts of queries in distributed databases, Proceedings of CIKM'2008, Napa Valley, USA, November 2008.
     
     
139. Norvald H. Ryeng and Kjetil Nørvåg, RIPPNET: Efficient Range Indexing in Peer-to-Peer Networks, Proceedings of ICDIM'2008, London, U.K., November 2008.
     
     
140. Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, Peer-to-Peer Similarity Search over Widely Distributed Document Collections, Proceedings of the 6th Workshop on Large-Scale Distributed Systems for Information Retrieval (LSDS-IR'08, in conjunction with CIKM'2008), Napa Valley, USA, October 2008.
     
     
141. Nattiya Kanhabua and Kjetil Nørvåg, Improving Temporal Language Models For Determining Time of Non-Timestamped Documents, Proceedings of the 12th European Conference on Research and Advanced Technology for Digital Libraries 2008 (ECDL'2008), Aarhus, Denmark, September 2008.
     
     
142. Norvald H. Ryeng and Kjetil Nørvåg, Robust Aggregation in Peer-to-Peer Database Systems, Proceedings of IDEAS'2008, Coimbra, Portugal, September 2008.
     
     
143. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, On Efficient Top-k Query Processing in Highly Distributed Environments, Proceedings of ACM SIGMOD'2008, Vancouver, Canada, June 2008.
     
     
144. Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, Schema-Assisted Peer Selection for XML Querying in Unstructured P2P Systems, Proceedings of the Seventh International ACM Workshop on Data Engineering for Wireless and Mobile Access (MobiDE'2008, in conjunction with SIGMOD'2008), Vancouver, Canada, June 2008.
     
     
145. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, Skyline-based Peer-to-Peer Top-k Query Processing, Proceedings of 24th IEEE International Conference on Data Engineering (ICDE'08), Cancun, Mexico, April 2008.
     
     
146. Kjetil Nørvåg, Eirik Eide, and Odin Hole Standal, Query Planning in P2P Database Systems, Proceedings of IEEE International Conference on Digital Information Management (ICDIM 2007), Lyon, France, October 2007.
     
     
147. Norvald H. Ryeng and Kjetil Nørvåg, Accuracy of Aggregation in Peer-to-Peer DBMSs, Proceedings of the 5th International Workshop on Databases, Information Systems and Peer-to-Peer Computing (DBISP2P 2007, in conjunction with VLDB'2007), September 2007.
     
     
148. Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, Scalable Semantic Overlay Generation for P2P-Based Digital Libraries, Proceedings of the 10th European Conference on Digital Libraries (ECDL'2006), Alicante, Spain, September 2006.
     
     
149. Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, Schema Caching for Improved XML Query Processing in P2P Systems, Proceedings of the 6th IEEE International Conference on Peer to Peer Computing, Cambridge, UK, September 2006.
     
     
150. Kjetil Nørvåg, Trond Øivind Eriksen, and Kjell-Inge Skogstad, Mining Association Rules in Temporal Document Collections, Proceedings the 16th International Symposium on Methodologies for Intelligent Systems (ISMIS'2006), Bari, Italy, September 2006.
     
     
151. Kjetil Nørvåg, DASCOSA: Database Support for Computational Science Applications, Proceedings of the 3rd International Workshop on Grid and Peer-to-Peer Computing Impacts on Large Scale Heterogeneous Distributed Database Systems (GLOBE'06), Krakow, Poland, September 2006.
     
     
152. Kjetil Nørvåg, Christos Doulkeridis, and Michalis Vazirgiannis, Taxonomy Caching: A Scalable Low-Cost Mechanism for Indexing Remote Contents in Peer-to-Peer Systems, Proceedings of IEEE International Conference on Pervasive Services 2006 (ICPS06), Lyon, France, June 2006.
     
     
153. Kjetil Nørvåg and Albert Overskeid Nybø, DyST: Dynamic and Scalable Temporal Text Indexing, Proceedings of the 13th International Symposium on Temporal Representation and Reasoning (TIME'2006), Budapest, Hungary, June 2006.
     
     
154. Kjetil Nørvåg and Albert Overskeid Nybø, Creating synthetic temporal document collections for Web Archive Benchmarking, Proceedings of the 4th Atlantic Web Intelligence Conference (AWIC'2006), Beer-Sheva, Israel, June 2006.
     
     
155. Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, The SOWES Approach to P2P Web Search using Semantic Overlays, Proceedings of the 15th World Wide Web Conference World Wide Web, Edinburgh, Scotland, UK, May 2006.
     
     
156. Michalis Vazirgiannis, Kjetil Nørvåg, and Christos Doulkeridis, Peer-to-Peer Clustering for Semantic Overlay Network Generation, Proceedings of the Sixth International Workshop on Pattern Recognition in Information Systems (PRIS-2006, co-located with ICEIS 2006), Paphos, Cyprus, May 2006.
     
     
157. Kjetil Nørvåg and Randi Øyri, News Item Extraction for Text Mining in Web Newspapers, Proceedings of International Workshop on Challenges in Web Information Retrieval and Integration (in conjunction with ICDE'2005), Tokyo, Japan, IEEE Computer Society April 2005.
     
     
158. Kjetil Nørvåg and Albert Overskeid Nybø, Improving space-efficiency in temporal text-indexing, Proceedings of the 10th International Conference on Database Systems for Advanced Applications (DASFAA 2005), Beijing, China, Springer Verlag April 2005.
     
     
159. Albrecht Schmidt and Kjetil Nørvåg, XML Database Application Development through a Stepwise Refinement Prototyping Process, Proceedings of ICEIS'2004, pages 370-375 (Vol 1), April 2004.
     
     
160. Efstratios Valavanis, Christopher Ververidis, Michalis Vazirgiannis, George C. Polyzos, and Kjetil Nørvåg, MobiShare: Sharing Context-Dependent Data & Services from Mobile Sources, Proceedings of the 2003 IEEE/WIC International Conference on Web Intelligence (WI 2003), pages 263-270, Halifax, Canada, IEEE Computer Society October 2003.
     
     
161. Kjetil Nørvåg, Space-Efficient Support for Temporal Text Indexing in a Document Archive Context, Proceedings of the 7th European Conference on Digital Libraries (ECDL'2003), pages 511-522, Trondheim, Norway, Springer Verlag August 2003.
     
     
162. Kjetil Nørvåg, V2: A Database Approach to Temporal Document Management, Proceedings of the 7th International Database Engineering and Applications Symposium (IDEAS'2003), pages 212-223, Hong Kong, China, IEEE Computer Society July 2003.
     
     
163. Kjetil Nørvåg, Marit Limstrand, and Lene Myklebust, TeXOR: Temporal XML Database on an Object-Relational Database System, Proceedings of Perspectives of System Informatics (PSI'03), Novosibirsk, Russia, July 2003. Revised version later published in post-conference proceedings by Springer Verlag (Lecture Notes in Computer Science; Vol 2890, pages 520-530).
     
     
164. Kjetil Nørvåg, The V2 Temporal Document Database System, Poster Proceedings of the Twelfth International World Wide Web Conference (WWW2003), Budapest, Hungary, May 2003.
     
     
165. Kjetil Nørvåg, Temporal XML Data Warehouses: Challenges and Solutions, Proceedings of Workshop on Knowledge Foraging for Dynamic Networking of Communities and Economies, Shiraz, Iran, October 2002.
     
     
166. Kjetil Nørvåg, Algorithms for Temporal Query Operators in XML Databases, Proceedings of XML-Based Data Management Workshop (XMLDM) (in conjunction with EDBT'2002), pages 36-47, Prague, Czech Republic, March 2002. Revised version later published in post-conference proceedings by Springer Verlag (Lecture Notes in Computer Science; Vol 2490, pages 169-183).
     
     
167. Kjetil Nørvåg, Temporal Query Operators in XML Databases, Proceedings of the 2002 ACM Symposium on Applied Computing (SAC'2002), pages 402-406, Madrid, Spain, ACM March 2002.
     
     
168. Kjetil Nørvåg, Object and Log Management in Temporal Log-Only Object Database Systems, Advances in Databases and Information Systems (Proceedings of ADBIS'2001), pages 210-224, , Lithuania. Springer Verlag (Lecture Notes in Computer Science; Vol 2151) 2001.
     
     
169. Kjetil Nørvåg, A Comparative Study of Log-Only and In-Place Update Based Temporal Object Database Systems, Proceedings of the Ninth ACM Conference on Information and Knowledge Management (ACM CIKM'2000), pages 496-503, Washington D.C., USA, ACM November 2000.
     
     
170. Kjetil Nørvåg, The Vagabond Temporal OID Index: An Index Structure for OID Indexing in Temporal Object Database Systems, Proceedings of the 2000 International Database Engineering and Applications Symposium (IDEAS), pages 158-166, Yokohama, Japan, IEEE Computer Society September 2000.
     
     
171. Kjetil Nørvåg, Design Issues in Transaction-Time Temporal Object Database Systems, Current Issues in Databases and Information Systems (Proceedings of ADBIS-DASFAA 2000), pages 371-378, Prague, Czech Republic. Springer Verlag (Lecture Notes in Computer Science; Vol 1884) 2000.
     
     
172. Kjetil Nørvåg, Main-Memory Management in Temporal Object Database Systems, Current Issues in Databases and Information Systems (Proceedings of ADBIS-DASFAA 2000), pages 362-370, Prague, Czech Republic. Springer Verlag (Lecture Notes in Computer Science; Vol 1884) 2000.
     
     
173. Kjetil Nørvåg, A Performance Evaluation of Log-Only Temporal Object Database Systems, Proceedings of the 12th International Conference on Scientific and Statistical Database Management, SSDBM 2000, Berlin, Germany, IEEE Computer Society July 2000.
     
     
174. Kjetil Nørvåg, An Approach to High-Performance Scalable Temporal Object Storage, Proceedings of the Workshop on High Performance Object Databases (HiPOD'2000), Cardiff, UK, July 2000.
     
     
175. Kjetil Nørvåg, The Persistent Cache: Improving OID Indexing in Temporal Object-Oriented Database Systems, Proceedings of the 25th International Conference on Very Large Databases (VLDB'99), pages 66-77, Edinburgh, Scotland, UK, 1999.
     
     
176. Kjetil Nørvåg, Efficient Use of Signatures in Object-Oriented Database Systems, Proceedings of Advances in Databases and Information Systems (ADBIS'99), pages 367-381, Maribor, Slovenia. Springer Verlag (Lecture Notes in Computer Science; Vol 1691) 1999.
     
     
177. Kjetil Nørvåg and Kjell Bratbergsengen, Optimizing OID Indexing Cost in Temporal Object-Oriented Database Systems, Proceedings of FODO'98, The 5th International Conference on Foundations of Data Organization, pages 137-146, Kobe, Japan, 1998.
     
     
178. Kjetil Nørvåg and Kjell Bratbergsengen, An Analytical Study of Object Identifier Indexing, Proceedings of DEXA'98, 9th International Conference on Database and Expert Systems Applications, pages 38-49, Vienna, Austria. Springer (Lecture Notes in Computer Science; Vol 1460) 1998.
     
     
179. Kjetil Nørvåg and Kjell Bratbergsengen, Write Optimized Object-Oriented Database Systems, Proceedings of the XVII International Conference of the Chilean Computer Science Society, SCCC'97, pages 164-173, Valparaiso, Chile. IEEE Computer Society 1997.
     
     
180. Kjetil Nørvåg and Kjell Bratbergsengen, Log-Only Temporal Object Storage, Proceedings of the 8th International Workshop on Database and Expert Systems Applications, DEXA'97, pages 728-733, Toulouse, France. IEEE Computer Society 1997.
     
     
181. Kjetil Nørvåg, Olav Sandstå, and Kjell Bratbergsengen, Concurrency Control in Distributed Object-Oriented Database Systems, Proceedings of ADBIS'97, pages 9-17, St.-Petersburg, Russia, 1997. Later also published in Advances in Databases and Information Systems, Electronic Workshops in Computing (eWiC), Springer-Verlag.
     
     
182. Kjell Bratbergsengen and Kjetil Nørvåg, Improved and Optimized Partitioning Techniques in Database Query Processing, Proceedings of BNCOD15, pages 69-83, London, United Kingdom. Springer Verlag (Lecture Notes in Computer Science; Vol 1271), 1997.
     
     
183. Kjetil Nørvåg and Olav Sandstå, Concurrency Control in Distributed Page-Server Systems, Proceedings of 3rd International Symposium on Programming and Systems, pages 44-56, Alger, Algerie, 1997.
     
     
184. Kjetil Nørvåg and Kjell Bratbergsengen, Aggregate and Grouping Functions in Object-Oriented Databases, Proceedings of the XVI International Conference of the Chilean Computer Science Society, SCCC'96, pages 67-76, Valdivia, Chile, 1996.
     
     
185. Kjetil Nørvåg, Neurocomputer Taxonomies, Proceedings of the World Congress on Neural Networks 1994, pages 596-600 (Vol. II), San Diego, 1994
     
     

National Conferences

186. Mei Saouk, Christos Doulkeridis, Akrivi Vlachou, and Kjetil Nørvåg, Efficient Processing of Top-k Joins in MapReduce, Proceedings of HDMS'2017, Athens, Greece, August 2017.
     
     
187. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis and Kjetil Nørvåg, Maximizing Influence of Spatio-Textual Objects Based on Keyword Selection, Proceedings of HDMS'2016, Athens, Greece, July 2016.
     
     
188. Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, Finding the Most Diverse Products using Preference Queries, Proceedings of HDMS'2015, Athens, Greece, July 2015.
     
     
189. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Yannis Kotidis, Branch-and-Bound Algorithm for Reverse Top-k Queries, Proceedings of HDMS'2014, Athens, Greece, July 2014.
     
     
190. João Batista da Rocha Junior, Akrivi Vlachou, Christos Doulkeridis and Kjetil Nørvåg, Efficient Algorithms for Top-k Spatial Preference Queries, Proceedings of HDMS'2012, Chania, Greece, June 2012.
     
     
191. Robert Neumayer, Krisztian Balog, Marek Ciglan, Wei Wei and Kjetil Nørvåg, Semantic Search for Entities in Structured Web Data: NTNU at the Yahoo Semantic Search Challenge 2011, Proceedings of Norsk Informatikkonferanse, Tromsø, Norway, November 2011.
     
     
192. Marek Ciglan and Kjetil Nørvåg, Anotacia ad-hoc dopytov pre semanticke vyhladavanie zoznamov entit, Proceedings of 6th Workshop on Intelligent and Knowledge oriented Technologies (WIKT'2011), Herlany, Slovakia, November 2011.
     
     
193. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg and Yannis Kotidis, Using Reverse Top-k Queries for Identifying the Most Influential Data Objects, Proceedings of HDMS'2011, Athens, Greece, July 2011
     
     
194. Akrivi Vlachou, Christos Doulkeridis, Yannis Kotidis and Kjetil Nørvåg Efficient Algorithms for Reverse Top-k Queries, Proceedings of HDMS'2010, Agia Napa, Cyprus, July 2010
     
     
195. Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg, and Michalis Vazirgiannis, Efficient Processing of Top-k Queries in P2P Networks, Proceedings of the 7th Hellenic Data Management Symposium (HDMS'08), Heraklion, Greece, July 2008
     
     
196. Kjetil Nørvåg, Christos Doulkeridis, and Michalis Vazirgiannis, The SOWES Approach to P2P Web Search using Semantic Overlays, Proceedings of the 5th Hellenic Data Management Symposium (HDMS'06), Thessaloniki, Greece, September 2006
     
     
197. Kjetil Nørvåg, Reducing the Cost of Perfect Match Accesses in Object Database Systems, Proceedings of Norsk Informatikkonferanse, Tromsø, Norway, November 2001.
     
     
198. Kjetil Nørvåg, The Vagabond Parallel Temporal Object-Oriented Database System: Versatile Support for Future Applications, Proceedings of Norsk Informatikkonferanse, pages 175-186, Trondheim, Norway, 1999.
     
     
199. Kjell Bratbergsengen and Kjetil Nørvåg, Optimizing Hash Partitioning in Relational Algebra, Proceedings of Norsk Informatikkonferanse 1996, Alta, Norway, November 1996.
     
     

Thesis

Unrefereed Papers and Technical Reports Containing Additional Unpublished Material

STUDENTS ADVISED

PhD Students

• Tomasz Kusmierczyk: Big data analytics (Ph.D., June 2018)
• Orestis Gkorgkas: Database content exploration and exploratory analysis of user queries (Ph.D., August 2015)
• Robert Neumayer: Semantic and Distributed Entity Search in the Web of Data (Ph.D., March 2013)
• Nattiya Kanhabua: Time-aware Approaches to Information Retrieval (Ph.D., February 2012)
• João Batista da Rocha Junior: Efficient Processing of Preference Queries in Distributed and Spatial Databases (Ph.D., January 2012)
• Norvald Ryeng: Improving Query Processing Performance in Large Distributed Database Management Systems (Ph.D., November 2011)

M.Sc. Students

• Tore Apeland Fossland: Semantic Similarity Search over Spatio-textual Data (2023)
• Lukas Nicholas Tveiten: Frameworks for Distributed Processing of Temporal Graph Queries (2023)
• Alexander Nes Fredheim: Group Betweenness Centrality on Dynamic Graphs (2022)
• Victor Jųrgensen: Predictive Modeling Using Pseudo-Social Networks Derived from Transaction Data (2022)
• Hans Kristian Sande: Predictive Modeling Using Pseudo-Social Networks Derived from Transaction Data (2022)
• Hedda Sofie Ulve: Utilizing Fine-Grained Transaction Data for Predicting the Life Event of Residential Change (2022)
• Jenny Jinyi Yu: Utilizing Fine-Grained Transaction Data for Predicting the Life Event of Residential Change (2022)
• Theodor René Carlsen : System for efficient storage and retrieval of dynamic graphs (2022)
• Eivind Kopperud: System for efficient storage and retrieval of dynamic graphs (2022)
• Peder Smith: Systems for Efficient Storage and Retrieval of Dynamic Networks (2022)
• Lise Presterud Hove: Mining Periodic Topic Trajectory Patterns in Spatiotemporal Textual Data (2021)
• Ingrid Seip Domben: Detecting Influential Events (2021)
• Marius Aleksander Kaasbøll: Exploring Exemplar Trajectory Queries (2021)
• Erik Nystø Rahka: Exploring Exemplar Trajectory Queries (2021)
• Kristian Kanck: TexTraClus - A Spatio-Textual Sub-Trajectory Clustering Framework (2020)
• Kjetil Kværnum: Incremental Update of Document Timestamping Models (2020)
• Hans Davies Sandbu: Spatiotemporal keyword search on RDF graphs (2020)
• Petter Thrane Bemelmans: Evaulation of S2R-tree (2020)
• Erlend Åmdal: Top-k Spatial Join on GPU (2020)
• Håvard Aspen Løvik: Top-k Spatial Join on GPU (2020)
• Arne Lyngstad Sund: Distributed distance-preserving graph approximations (2020)
• Didrik Pemmer Aalen: Document Dating Using Temporal Information Extracted From Wikipedia (2018)
• Eirik Rognø: Efficient spatio-interval join (2018)
• Christian Barth Roligheten: Cumulative Citation Recommendation (2018)
• Lars Martin Bævre Ek: Durability in a data-flow storage system (2018)
• Truls Rustad Fossum: Efficient Spatial Search using Memory Resident R-trees (2017)
• Øyvind Nygard: Automatic Document Timestamping (2017)
• Kristoffer Berg Gumpen: Automatic Document Timestamping (2017)
• Tord Kloster: Spatio-textual search on Spark (2017)
• Sigurd Sandve: A metadata approach to predicting Twitter user geolocation (2016)
• Stella Maropaki: A study on algorithms for maximizing the influence score of spatio-textual objects (co-supervised with Christos Doulkeridis, 2016)
• Simen Skoglund: Authorship Identification of Research Papers (August 2015)
• Sebastian Zalewski: Mining Frequent Intra- and Inter-Transaction Itemsets on Multi-Core Processors (2015)
• Hågvard Lund Eidheim: Temporal Summarization of Time Critical Events (2015)
• Vegard Harper: Density-Based Spatial Clustering with Application and Noise with Spark (2015)
• Ellen Wiig Andresen: Novelty Detection in Knowledge Base Acceleration (2013)
• Stian Liknes: Database Operations on Multi-Core Processors (2013)
• Eirik Emanuelsen: Event Detection using Wikipedia (2013)
• Martin Rudi Holaker: Event Detection using Wikipedia (2013)
• Ken Oscar Grønnbeck: Continuously adapting continuous Queries for Data Streams in Raincoat (2013)
• Steffen Rendahl Stenersen: Continuously adapting continuous Queries for Data Streams in Raincoat (2013)
• Jan Rybak: Financial Information Extraction and Visualization (2013)
• Eivind Bjørkelund: Temporal opinion mining (2012)
• Thomas Hoberg Burnett: Temporal opinion mining (2012)
• Øystein Egeland Carlsson: Keyword Search on Spatial Network Databases - Road network indexing for efficient query processing (main supervisor João Batista da Rocha Junior, 2011)
• Martin Nordseth Torgersen: System for Distributed Text Mining (2011)
• Adrian Viaño Iglesias: Graph representation of documents content and its suitability for text mining tasks (main supervisor: Marek Ciglan, 2011)
• Hanjie Shue: Opinion mining for song lyrics (main supervisor: Robert Neumayer, 2010)
• Gaojie He: Authoritative K-Means for Clustering of Web Search Results (main supervisor: Robert Neumayer, 2010)
• Konrad Giæver Beiske: Semantic Cache Investment; Adaption of Cache Investment for DASCOSA (main supervisor: Jon Olav Hauglid, 2009)
• Jan Bjørndalen: Semantic Cache Investment; Adaption of Cache Investment for DASCOSA (main supervisor: Jon Olav Hauglid, 2009)
• Øystein Løhre Garnes: Feature Selection for Text Categorization (co-supervised with Robert Neumayer, 2009)
• Magnus Galåen: Text clustering (2008)
• Svein Aga: System Reconfiguration in Large-Scale Distributed Storage Systems (2008)
• Christian Bøhn: Using Wikipedia to Find Entities in News (2008)
• Ole Kristian Fivelstad: Temporal Text Mining (2007)
• Knut Auvor Grythe: Automated tuning of MapReduce performance in Vespa Document Store (2007)
• Norvald Ryeng: Churn Resilent Aggregation in Peer-to-Peer Query Networks (2006)
• Eirik Eide: PORDaS: P2P Object-Relational Database System (2006)
• Odin Standal: PORDaS: P2P Object-Relational Database System (2006)
• Trond Øivind Eriksen: A Searcher plug-in for the Yahoo! vertical search platform Combining Ranking and Aggregation (2006)
• Anne Siri Korsen: A Searcher plug-in for the Yahoo! vertical search platform Combining Ranking and Aggregation (2006)
• Bjørn Engelberg: Storage Grid (2005)
• Erik Bråten: Temporal XML-database (2004)
• Albert Overskeid Nybø: Temporal text indexing (2004)
• Randi Øyri: Text mining in web newspapers (2004)
• Marit Limstrand: Temporal XML Database (2002)
• Lene Myklebust: Temporal XML Database (2002)
• Kåre Fosse (1998)
• Anders Alstad (1997)
• Tor Rune Skoglund (1997)
• Knut Aage Aksnes (1997)

SCIENTIFIC SERVICE

Service

• Member of Board of Directors, SSTD Endowment (Symposium on Spatial and Temporal Databases), 2020-.
• Member of Steering Committee, European Conference on Advances in Databases and Information Systems (ADBIS), 2020-.
• Program co-chair, 29th European Conference on Advances in Databases and Information Systems (ADBIS'2025), Tampere, Finland, September 2025.
• General co-chair, 44th European Conference on Information Retrieval (ECIR'22), 2022.
• Workshop co-chair, 6th European Conference on Advances in Databases and Information Systems (ADBIS'2022), Torino, Italy, September 2022.
• Program co-chair, 16th International Symposium on Spatial and Temporal Databases 2019 (SSTD 2019), Vienna, Austria, August 2019.
• Program co-chair, 25th International Symposium on Temporal Representation and Reasoning (TIME'2018), Warsaw, Poland, October 2018.
• Program co-chair, 21st European Conference on Advances in Databases and Information Systems (ADBIS'2017), Nicosia, Cyprus, September 2017.
• Workshop co-chair, 21st International Conference on Theory and Practice of Digital Libraries (TPDL'2017), Thessaloniki, Greece, September 2017.
• Editorial board, Information Processing & Management (IPM), Elsevier, 2016-.
• Doctoral Consortium co-chair, 20th International Conference on Theory and Practice of Digital Libraries (TPDL'2016), Hannover, Germany, September 2016.
• Co-chair, Workshops, 29th International Conference on Data Engineering (ICDE'2013), Brisbane, Australia, April 2013.
• Editorial board, TLDKS Transactions on Large-Scale Data and Knowledge-Centered Systems (TLDKS), Springer, 2014-2018.
• Location manager at the 31st International Conference on Very Large Data Bases (VLDB'2005), Trondheim, Norway, 2005.

Program Commitees

• 2025: WSDM'2025.
• 2024: ICDE'2024, WSDM'2024, IEEE BigData 2024, ADBIS'2024, BDMA'2023, TempWeb'2024, TPDL'2024 (Short track).
• 2023: SIGSPATIAL'2023, SSTD'2023, WSDM'2023, TheWebConf'2023, ICDE'2023 (Demo track), ECIR'2023 (Senior PC and Workshop), DAWAK'2023, TPDL'2023 (Short track), ADBIS'2023, TempWeb'2023, BMDA'2023, DOLAP'2023, DARLI-AP'2023, LocalRec'2023.
• 2022: TheWebConf'2022, ICDE'2022 (Demo track), DASFAA'2022, LocalRec'2022, ADBIS'2022, TPDL'2022 (Short/demo track), DaWak2022, TempWeb'2022, DARLI-AP'2022, DOLAP'2022.
• 2021: ICDE'2021 (Demo track), SSTD'2021, DASFAA'2021, TPDL'2021, DOLAP'2021, ECIR'2021 (Demo track), ADBIS'2021, DARLI-AP'2021, DAWAK'2021, TempWeb'2021, LocalRec'2021.
• 2020: DASFAA'2020, TIME'2020, TPDL'2020, ADBIS'2020, DOLAP'2020, TempWeb'2020, DARLI-AP'2020, GeoRich'2020, LocalRec'2020.
• 2019: ECML PKDD 2019, DASFAA'2019, TPDL'2019, ADBIS'2019, DOLAP'2019, CICLing'2019, DSMM'2019, DARLI-AP'2019, TempWeb'2019, LChange'19, LocalRec'2019.
• 2018: SIGMOD'2018, ICDE'2018, EDBT'2018, ECML-PKDD'2018, DASFAA'2018, ADBIS'2018, TPDL'2018, CICLing'2018, ExploreDB'2018, TempWeb'2018, DOLAP'2018, BDMICS'2018, DARLI-AP'2018, MATES'18, HealthRecSys'2018.
• 2017: EDBT'2017, ECML PKDD'2017, DASFAA'2017, TPDL'2017, JCDL'2017, CICLing'2017, IEEE BigDataService'2017, TempWeb'2017, KARS'2017, MSM'2017, IDC'2017, ExploreDB'2017, MATES'17, TDDL'2017, HealthRecSys'2017, i-KNOW'2017, LocalRec'2017.
• 2016: EDBT'2016, ECML PKDD'2016, SSDBM'2016, VLDB'2016 (demo track), CICLing'2016, JCDL'2016, WISE'2016, TempWeb'2016, BDPR'2016, ExploreDB'2016, IEEE BigDataService'2016, MSM'16, BDMICS'2016.
• 2015: ECML PKDD'2015, JCDL'2015, TPDL'2015, CICLing'2015, TIME'2015, WISE'2015, IEEE BigDataService 2015, ADBIS'2015, DASFAA'2015 (demo track), ExploreDB'2015, LocWeb'2015, TempWeb'2015, Globe'2015, MSM'2015, SPS'2015, SOMERIS'2015.
• 2014: ECML PKDD'2014 (main track), ECML PKDD'2014 (demo track), DL2014 (TPDL2014/JCDL2014), TIME'2014, CICLing'2014, ADBIS'2014, Globe'2014, ExploreDB'2014, TempWeb'2014, WISE'2014, LocWeb2014.
• 2013: EDBT'2013, TPDL'2013, CICLing'2013, TempWeb'2013, IDEAS'2013, GLOBE'2013, ADBIS'2013, LBS n.0., WISE'2013.
• 2012: ADBIS'2012, CICLing'2012, SRDS'2012, TempWeb'2012, TPDL'2012, Globe'2012.
• 2011: EDBT'2011, ECML PKDD'2011, CICLing'2011, TWAW'2011, TPDL'2011, Globe'2011, MIND'2011.
• 2010: ICDE'2010 (demo track), Globe'2010, ECDL'2010, LSDS-IR'2010, IWAW'10.
• 2009: SIGMOD'2009, ADBIS'2009, Globe'09, LSDS-IR'2009, IWAW'09.
• 2008: ICDIM'2008, IWAW'08, Globe'08.
• 2007: ADBIS'2007.
• 2006: WAW'06, ADBIS'2006, CSI 2006, Baltic DB&IS'2006, CSIT'2006.
• 2005: IWAW'05, ADBIS'2005, CSI 2005.
• 2004: IWAW04, ADBIS'2004.
• 2003: WebArchiving'2003. ADBIS'2003, CSI'2003.
• 2002: 2nd Annual International Workshop of the Working Group "Web and Databases" of the German Informatics Society (GI) (Held in conjunction with Net.ObjectDays 2002 (NODe '02), CSI'2002.

ACTIVITIES

• Head of the Data and Information Management group, 2009-2013.
• Deputy leader of the departmental research committee, 2009-2011.
• Member of committee for evaluation of the PhD study at IME-faculty, NTNU, 2007.
• Member of the jury of the Rosing Student Prize, 2005-2007.
• Member of board of Computational Science and Visualization Program at NTNU, 2004-2008.
• Working group leader for Computer Systems area in InfoSam2020 - The Information Society of 2020 -an exercise in planning for the future, 2004.
• Participant in storage subproject of NOTUR Competency projects on GRID, Cluster and Storage Technologies, 2004.
• Member of evaluation committee for associate professorship at the Computer Architecture and Design Group, NTNU, 2004.
• Member of the jury of the Rosing Student Prize, 2003.
• The board of the Computer Science department at NTNU, elected deputy member, 1998-99.
• The board of the Computer Science department at NTNU, elected member, 1996-98.
• Elected representative for the soldiers at the Royal Norwegian Airforce Academy, 1993-94.
• The board of the Akademisk Radioklubb (Norwegian for 'academic radio club'), vice chair, 1990-91.

LECTURING EXPERIENCE

• Big Data Architecture. Spring 2023.
• Big Data Architecture. Spring 2022.
• Big Data Architecture. Spring 2021.
• Big Data Architecture. Spring 2020.
• Data warehousing and data mining. Spring 2020.
• Big Data Architecture. Spring 2018.
• Data warehousing and data mining. Spring 2018.
• Big Data Architecture. Spring 2017.
• Data warehousing and data mining. Spring 2017.
• Big Data Architecture. Spring 2016.
• Data warehousing and data mining. Spring 2016.
• Data warehousing and data mining. Spring 2015.
• Advanced database systems. Fall 2014.
• Data warehousing and data mining. Spring 2013.
• Advanced database systems. Fall 2012.
• Advanced database systems. Spring 2012.
• Data warehousing and data mining. Spring 2012.
• Advanced database systems. Spring 2011.
• Advanced database systems. Spring 2010.
• Advanced information retrieval. Spring 2010.
• Information retrieval. Fall 2009.
• Advanced database systems, (4th year course, 30 students). Spring 2008.
• Distributed systems, (3rd/4th year course, 70 students). Spring 2007.
• Data modelling and database systems, (2rd year course, 250 students). Spring 2007.
• Operating Systems, (3rd year course, 220 students). Fall 2006.
• Data mining, (5th year course, 15 students). Fall 2006.
• Data modelling and database systems (2nd year course, 180 students). Spring 2006.
• Data mining, (5th year course, 15 students). Fall 2005.
• Database systems (2nd year course, approx. 65 students). Fall 2005.
• Data mining, (5th year course, 6 students). Fall 2004.
• Data modelling and database systems (2nd year course, 300 students). Spring 2004.
• Semistructured data (5th year course, 10 students). Fall 2003.
• Database systems (2nd year course, approx. 40 students). Fall 2003.
• Algorithms and data structures (2nd year course, approx. 100 students). Spring 2002.
• Computer architecture and operating systems (3rd year course). Lecturing the computer architecture part of the course. Fall 2001.
• Computer architecture and operating systems (3rd year course). Lecturing the computer architecture half of the course. Fall 2000.
• Computer architecture (4th year course). Spring 2000.
• Computer architecture and operating systems (3rd year course, 170 students). Lecturing the computer architecture half of the course. Fall 1999.
• Computer architecture (4th year course, 28 students). Spring 1999.
• Computer systems (3rd year course, 210 students). Fall 1998.

• Temporal infomation retrieval.
• Advanced topics in database systems.
• Web mining.

Fluent in English, written and oral. Have a very good understanding of other Scandinavian languages.

HOBBIES AND INTERESTS

Traveling (have currently visited over over 70 countries and 25 Greek islands), photography, music, literature, Latin American history and politics, Greece.