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Toon Calders

  • Research Expertise:Analysis of dynamic network data Most works in network analysis concentrate on static graphs and find patterns such as the most in influential nodes in the network. Very few existing methods are able to deal with repeated interactions between nodes in a network. The main goal of the research in this topic is hence to fill this gap by developing methods to identify patterns in interactions between network nodes. We studied so-called information channels that indicate information flows. Process Mining In process mining the object of study are logs generated by business processes. Consider for instance a log generated by a leave request system, recording activities such as users logging in, opening a new request, managers approving requests, emails being sent by the system, etc. In process mining such logs are analyzed to better understand, monitor, and improve the business processes. One tasks in this context is detecting complex events. Complex events can be used to find pre-defined security problems or abnormalities. Often, however, anomalies may occur that are not foreseen in the systems. In order to be able to handle such cases, anomaly detection techniques are necessary. With the following work on model-based anomaly detection using dynamic Bayesian networks, we won the Business Process Intelligence challenge at the BPM 2018 conference: S. Pauwels and T. Calders. Detecting and Explaining Drifts in Yearly Grant Applications. In BPM Workshop Business Process Intelligence (BPI), 2018. Fairness-Aware Machine Learning In contemporary society we are continuously being profiled; banks have profiles to divide up people according to credit risk, insurance companies profile clients for accident risk, telephone companies profile users on their calling behavior, web corporations profile users according to their interests and preferences based on web activity and visitation patterns. These profiles are more and more built automatically by machine learning methods trained on historical data. Within society there are growing concerns that these machine learning methods do not have ethical or moral restrictions. Recent studies show indeed that in circumstances where historical data is biased, or when there is omitted variable bias, automatically learned methods may take decisions that could be considered discriminatory. Apart from ethical considerations, there are also legal restrictions to the use of profiling methods that blindly optimize accuracy without taking unwanted discriminatory effects into account. The recent General Data Protection Regulation (GDPR; Regulation (EU) 2016/679) explicitly mentions profiling (Art. 22 GDPR Automated individual decision-making, including profiling) as an activity in which decisions should not be based on personal data and suitable measures should be in place to safeguard the data subjects rights and freedoms and legitimate interests. Most profiling techniques, however, do not consider anti-discrimination legislation and may unintentionally produce models that are unfair and hence do not safeguard the data subjects freedoms. A further complication is that often detecting whether a model is unfair, is highly non-trivial.
  • Keywords:PATTERN MINING, Computer science (incl. applied informatics)
  • Disciplines:Data mining, Machine learning and decision making
  • Research techniques:- Formalizing research problems mathematically; - Development of algorithmic solutions; - Study of computational properties of algorithms; - Case studies: application of developed techniques in real-life contexts.
  • Users of research expertise:All sectors in which machine learning is applied, including: - default prediction in the financial sector; - risk assessment in insurance; - outlier detection from log files for security monitoring; - predictive modelling. There are existing collaborations with insurance companies (fairness in machine leanring - building fair score models), bankin sector (default prediction), scientific institutes (BIRA: analysis of spectrograms for meteor detection),...