Saulo Martiello Mastelini is currently pursuing the Ph.D. degree with the Institute of Mathematics and Computer Science, University of São Paulo (USP), São Carlos, Brazil. He is also a Collaborator and a former Visiting Researcher with the Laboratory of Artificial Intelligence and Decision Support (LIAAD), Institute for Systems and Computer Engineering, Technology and Science (INESC TEC)/Universidade do Porto, Porto, Portugal. He is also one of the founders and maintainers of the River library for online machine learning in Python. His research interests include decision trees, decision rules, ensemble learning, nearest neighbor search, and concept drift analysis.