PeopleofSuperintelligence

Researcher

Janez Demšar

Also known as Janez Demsar

Janez Demšar is a computer scientist at the University of Ljubljana whose research covers machine learning, visualization and statistics, and who helps develop the open-source Orange data-analytics system. His 2006 paper "Statistical Comparisons of Classifiers over Multiple Data Sets" in the Journal of Machine Learning Research recommended the Wilcoxon signed ranks test and the Friedman test for comparing classifiers and introduced critical difference diagrams. In 2013, he was first author of the JMLR paper "Orange: Data Mining Toolbox in Python", and in 2022 he and Blaž Zupan received Slovenia's Puh Prize for outstanding achievements for developing Orange. The Student Council of the Faculty of Computer and Information Science gave him its best teacher award in every year from 2008 to 2024 except 2018. He is a full professor at the University of Ljubljana and works on school projects such as Pumice and DALI4US that bring AI and data exploration into classrooms.

Timeline

  1. 1999

    Learning concept hierarchies

    He coauthors "Learning by discovering concept hierarchies" with Blaž Zupan, Marko Bohanec and Ivan Bratko, published in Artificial Intelligence in 1999.

  2. 2006

    Comparing classifiers across data sets

    His paper "Statistical Comparisons of Classifiers over Multiple Data Sets" appears in the Journal of Machine Learning Research in 2006. It recommends the Wilcoxon signed ranks test for comparing two classifiers and the Friedman test with post-hoc tests for comparing more, and introduces critical difference diagrams to present the results.

  3. 2008–2024

    Best teacher at FRI

    The Student Council of the Faculty of Computer and Information Science gives him its best teacher award in every year from 2008 to 2024 except 2018. From summer 2013, he is responsible for the faculty's summer schools for elementary school students.

  4. 2012–2013

    Orange history and toolbox paper

    In 2012, he gives the last talk at a Slovene AI Society anniversary event, on the birth, history and future of Orange, a project that goes back to 1997 and Donald Michie's idea of an open machine learning toolbox. In 2013, he is first author of "Orange: Data Mining Toolbox in Python" in the Journal of Machine Learning Research, with 15 coauthors including Blaž Zupan.

  5. 2014–2017

    State award and Golden Plaque

    The Slovenian Ministry of Science, Education and Sports gives him a state award for achievements in higher education in 2014. In 2017, the University of Ljubljana awards him its Golden Plaque for Merits in the Development of the University of Ljubljana.

  6. 2022

    The Puh Prize for Orange

    He and Blaž Zupan receive Slovenia's Puh Prize for outstanding achievements in 2022 for developing the Orange data analytics and machine learning tool. The Ministry of Education, Science and Sport describes Orange as a significant contribution to the global data revolution and the democratisation of artificial intelligence.

  7. 2023–2024

    AI and data in schools

    In May 2023, he and Anja Mejač report on a Pumice challenge, part of the project "Pouk s ščepcem umetne inteligence" (Teaching with a Pinch of Artificial Intelligence): 50 teachers from 30 schools take part and almost one thousand students finish it. In 2024, he and Blaž Zupan lead hands-on workshops in Laško, Slovenia, for teachers from Ireland, Luxembourg and Slovenia in the Erasmus+ project DALI4US.

  8. As of October 2026

    Professor at Ljubljana

    He is a full professor teaching at the Faculty of Computer and Information Science and the Faculty of Education of the University of Ljubljana, and a member of its Bioinformatics Laboratory. His research focuses on machine learning, visualization and statistics, and he contributes to the development of Orange. His current projects include DALI4US on data literacy for upper primary schools (2024–2026) and a research project on explainable foundation models for human gene expression (2025–2027).

  1. The United States employs an estimated 48% of people shaping AIIncludes University of Ljubljana. We estimate where the people shaping AI work today, how universities, companies and research institutes split across countries, and how country shares have changed since the 1960s.
  2. More people shaping AI studied at Massachusetts Institute of Technology than at any other institutionIncludes University of Ljubljana. We estimate where the people shaping AI studied and where their careers led. Massachusetts Institute of Technology leads with 467 former students, including 291 recorded doctorates.
  3. The company share of AI researchers’ top papers was 31% in 2020–2024 and 8% in 1970–1974Includes University of Ljubljana. We estimate where the people shaping AI worked when their most-cited papers appeared: the company share was 31% in 2020–2024 and 8% in 1970–1974, and Google led all organizations in 2020–2024.
  4. Google had the most people shaping AI every year from 2014 to 2025Our estimates of which organizations employed the most people shaping AI each year from 1955 to 2025, tracing the shift from university labs to companies.

Colleagues

People named in this biography, and people with dated positions at the same organization in the same years.

Sources and credits

Photo: We have no published photo of Janez Demšar yet. Send us a free-licensed photo.

  1. Blaž Zupan - Wikipedia en.wikipedia.org. Checked 21 October 2026.
  2. Statistical Comparisons of Classifiers over Multiple Data Sets jmlr.org. Checked 21 October 2026.
  3. Janez Demšar - Ljubljana - FRI fri.uni-lj.si. Checked 21 October 2026.
  4. Orange Data Mining - history oldorange.biolab.si. Checked 21 October 2026.
  5. Orange: Data Mining Toolbox in Python jmlr.org. Checked 21 October 2026.
  6. Award ceremony for the highest state prizes and awards in science | GOV.SI gov.si. Checked 21 October 2026.
  7. Orange Data Mining - Pumice challenge orangedatamining.com. Checked 21 October 2026.
  8. Orange Data Mining - Developing Data Literacy in European Primary Schools with Orange orangedatamining.com. Checked 21 October 2026.