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DOI: 10.4230/OASIcs.DX.2026.3

Dissecting NetDoktor’s Online Questionnaire with Entropy, Tree Simplification & Logical Abduction

Authors: Alexander Perko, Emir Mujić, and Franz Wotawa

Published in: OASIcs, Volume 148, 37th International Conference on Principles of Diagnosis and Resilient Systems (DX 2026)

Abstract

Medical diagnosis and its accuracy are dependent on the available information. Hence, it is in the interest of both the patient and the doctor to provide the necessary information and ask the right questions in an efficient manner. The same can be said about medical questionnaires, which resemble the conversation during a doctor’s appointment. NetDoktor’s SymptomChecker is a freely accessible, expert-curated questionnaire in the German language. It can be traversed like a large decision tree, linking symptoms to diseases. However, does it find an optimal conversation path to acquire the necessary information from its users? Here, our study surfaces structural deficiencies and ways to optimise the questionnaire paths. In particular, we model the process of acquiring information and refining prognoses as an abductive reasoning problem and provide a corresponding algorithm. In our experiments, we apply simple tree transformations and optimisations, building upon Shannon’s information entropy to expose redundant subtrees and inefficient question order. Our results contribute to a better understanding of medical questionnaires and open the door for future applications of the data provided by NetDoktor. Because SymptomChecker is validated by medical professionals, it is a prime candidate to serve as a reference for benchmarking other systems. For instance, a dataset derived from SymptomChecker can be used for testing systems such as large language models in the task of medical diagnosis.

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Alexander Perko, Emir Mujić, and Franz Wotawa. Dissecting NetDoktor’s Online Questionnaire with Entropy, Tree Simplification & Logical Abduction. In 37th International Conference on Principles of Diagnosis and Resilient Systems (DX 2026). Open Access Series in Informatics (OASIcs), Volume 148, pp. 3:1-3:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{perko_et_al:OASIcs.DX.2026.3,
  author =	{Perko, Alexander and Muji\'{c}, Emir and Wotawa, Franz},
  title =	{{Dissecting NetDoktor’s Online Questionnaire with Entropy, Tree Simplification \& Logical Abduction}},
  booktitle =	{37th International Conference on Principles of Diagnosis and Resilient Systems (DX 2026)},
  pages =	{3:1--3:20},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-455-0},
  ISSN =	{2190-6807},
  year =	{2026},
  volume =	{148},
  editor =	{Pill, Ingo and Zanella, Marina and Provan, Gregory},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.DX.2026.3},
  URN =		{urn:nbn:de:0030-drops-278173},
  doi =		{10.4230/OASIcs.DX.2026.3},
  annote =	{Keywords: Medical Questionnaire, Diagnosis, Abductive Reasoning, Information Entropy}
}

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Short Paper

DOI: 10.4230/OASIcs.DX.2026.16

Counterfactual Fault Responsibility in a Dynamic Structural Causal Model of a DC Motor (Short Paper)

Authors: Emir Mujić and Franz Wotawa

Published in: OASIcs, Volume 148, 37th International Conference on Principles of Diagnosis and Resilient Systems (DX 2026)

Abstract

Model-based diagnosis can identify fault hypotheses that are compatible with observed abnormal behaviour. Still, it does not necessarily determine which fault is responsible for a particular symptom when several faults are active simultaneously. We propose a counterfactual framework for post-diagnostic fault responsibility analysis in dynamical systems. The physical process is represented as a time-indexed structural causal model, while faults are encoded as interventions on individual system mechanisms. Responsibility is evaluated by comparing the factual system trajectory with counterfactual trajectories in which candidate faults are removed while the operating conditions and control structure are kept fixed. We instantiate the framework on an electro-thermo-mechanical model of a DC motor and evaluate it in two simulated multi-fault scenarios. The results show that counterfactual fault removal can separate the contributions of different faults to individual symptoms and distinguish severity contribution from necessity for a failure event. The proposed approach therefore complements conventional diagnosis with symptom-level causal explanations of faulty system behaviour.

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Emir Mujić and Franz Wotawa. Counterfactual Fault Responsibility in a Dynamic Structural Causal Model of a DC Motor (Short Paper). In 37th International Conference on Principles of Diagnosis and Resilient Systems (DX 2026). Open Access Series in Informatics (OASIcs), Volume 148, pp. 16:1-16:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{mujic_et_al:OASIcs.DX.2026.16,
  author =	{Muji\'{c}, Emir and Wotawa, Franz},
  title =	{{Counterfactual Fault Responsibility in a Dynamic Structural Causal Model of a DC Motor}},
  booktitle =	{37th International Conference on Principles of Diagnosis and Resilient Systems (DX 2026)},
  pages =	{16:1--16:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-455-0},
  ISSN =	{2190-6807},
  year =	{2026},
  volume =	{148},
  editor =	{Pill, Ingo and Zanella, Marina and Provan, Gregory},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.DX.2026.16},
  URN =		{urn:nbn:de:0030-drops-278304},
  doi =		{10.4230/OASIcs.DX.2026.16},
  annote =	{Keywords: Counterfactual Reasoning, Fault Responsibility, Structural Causal Models, Dynamic Systems, Model-Based Diagnosis}
}

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Documents authored by Mujić, Emir

Dissecting NetDoktor’s Online Questionnaire with Entropy, Tree Simplification & Logical Abduction

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Counterfactual Fault Responsibility in a Dynamic Structural Causal Model of a DC Motor (Short Paper)

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