M.Sc. Sascha Marton: "Learning Axis-Aligned Decision Trees with Gradient Descent"


Decision Trees (DTs) are commonly used for many machine learning tasks due to their high degree of interpretability. However, learning a DT from data is a difficult optimization problem, as it is non-convex and non-differentiable. Therefore, common approaches learn DTs using a greedy growth algorithm that minimizes the impurity locally at each internal node. Unfortunately, this greedy procedure can lead to inaccurate trees. In this talk, I present a novel approach for learning hard, axis-aligned DTs with gradient descent. The proposed method uses backpropagation with a straight-through operator on a dense DT representation, to jointly optimize all tree parameters. The approach outperforms existing methods on binary classification benchmarks and achieves competitive results for multi-class tasks.

M.Sc. Sascha Marton

Sascha Marton - scientific researcher at the University of Mannheim's Institute for Enterprise Systems (InES)


Prof. Dr. rer.nat. Reiner Hähnle: "Simulation with Active Object Languages"


Active Objects are an increasingly popular programming language paradigm, characterized by asynchronous task execution, strong data encapsulation, and explicit synchronization to minimize data races. We discuss, as a representative example, the Active Object language ABS and illustrate how it is used in different simulation scenarios. ABS has extensions for timed as well as for hybrid systems. Together with a high level of abstraction, this makes it an interesting candidate for simulation models.

Prof.Dr. rer.nat. Reiner Hähnle

Prof.Dr. rer.nat. Reiner Hähnle - leader of the research group "Software Engineering" at the TU Darmstadt


Prof. Dr. Michael Sedlmair: "Immersive and Situated Analytics: Pitfalls, Challenges, and Opportunities"


Interactive visualization has evolved into an established field and is utilized by thousands of people every day. Currently, most visualization tools are optimized for desktop usage, and some for mobile devices. However, with the enormous push of Virtual Reality and Augmented Reality (VR/AR), these display modalities are gaining increasing importance in visualization, giving rise to the emerging areas of immersive and situated analytics. In this talk, I will reflect on the experiences from our 5-year endeavor to bridge Visualization and VR/AR research. Through case studies of our attempts at VR/AR-based visualizations, we will discuss pitfalls, challenges, and the opportunities that this area offers.

Prof.Dr. Michael Sedlmair

Prof. Dr. Michael Seldmair - professor at the University of Stuttgart's Institute for Visualization and Interactive Systems, and leader of the research group for Visualization and Virtual/Augmented Reality


Jun.-Prof. Dr.-Ing. Stefan Lüdtke: "Combining Mechanistic Models and Machine Learning for Digital Twins of the Ocean"


Recently, deep learning methods have been extremely successful for domains like natural language processing or computer vision. However, such data-driven methods are still insufficient for domains where training data is scarce, like modeling and prediction of ecosystem dynamics. On the other hand, mechanistic models or simulation models are less dependent on large training data sets, but can be less flexible and accurate when the true system dynamics is not completely captured by the model. In this talk, I will give an overview of research efforts that aim to integrate these two modeling concepts. Specifically, I will present methods for utilizing simulation models for training data generation, knowledge distillation, and neuro-symbolic models. I will give some examples from our own research, including hybrid models for modeling ecosystem dynamics and sensor-based activity recognition.

Jun.-Prof.Dr.-Ing Stefan Lüdtke

Jun.-Prof.Dr.-Ing Stefan Lüdtke  - head of the chair for Marine Data Science


Prof.Dr.-Ing. Uwe Freiherr von Lukas: "Digital Twins of the Ocean"


In my presentation on Digital Twins of the Ocean, I will start with a motivation for this topic and an overview of the general concept. It is followed by illustrative examples in the four areas that jointly enable the idea of a Digital Twin: Acquisition of marine data, (federated) data management, analytics & simulation, and visualization & interaction. By this, the talk gives a summary of the research activities of the chair Maritime Graphics and the maritime departments of Fraunhofer IGD.. 

Prof. Dr.-Ing. Uwe Freiherr von Lukas

 Prof. Dr.-Ing. Uwe Freiherr von Lukas - head for Martime Graphics and site manager of Fraunhofer IGD Rostock


Prof.Dr. Oliver Staadt: "Deep Learning for Visual Computing: An Introduction to Inverse Rendering and Neural Radiance Fields"


Inverse rendering is the process of recovering the properties of a scene from images, such as its geometry, lighting, and materials. Neural radiance fields (NeRFs) are a type of deep learning model that can be used for inverse rendering. NeRFs represent a 3D scene as a continuous function that maps from 3D points to RGB colors and opacity values.

In this short talk,  I will give an introduction to inverse rendering and NeRFs. I will discuss the basic principles of inverse rendering, and how NERFs can be used to solve this problem. 

Prof. Dr. Oliver Staadt

 Prof. Dr. Oliver Staadt - head of the chair of Visual Computing


Dr. Sebastian Bader "An Introduction to Transformer Models and Neural Text Processing"


In this short presentation, I will cover the basic ideas of handling texts in neural networks, handling sequences and finally building transformer models. First, I will show how to represent and reason about textual data within neural networks, by introducing word2vec models - how to build and how to use them.  Then, I will show how to handle sequence data in recurrent architectures. Finally, I will introduce transformer models, by describing their general architecture, underlying ideas and assumptions and show how to train them.

Dr. Sebastian Bader

 Dr. Sebastian Bader ist a staff member of the chair MMIS.


Staff members of the chair MOSI and the Thünen Institute for Baltic Sea Fisheries: "A Zoo of Models"


The talk "A Zoo of Models" will give an overview of simulation studies conducted at the modeling and simulation group. The simulation studies address research questions as diverse as analyzing differences of mitochondria in healthy and less healthy cells, illuminating the interplay of osteoblasts and osteoclasts in their response to electrical stimulation, studying environmental influences on cod metabolism, or exploring possible effects of specific governmental regulations on recreational fishery. Extracts of simulation models and their provenance, including different data sources and simulation experiments, will be presented. The simulation studies will illuminate the role of different modeling approaches in answering the research questions and dealing with uncertainties in studying intra-cellular, inter-cellular, ecological, and socio-ecological systems.

Staff members of the chair MOSI and the Thünen Institute for Baltic Sea Fisheries

 MOSI: Prof.Dr. Adelinde Uhrmacher, Dr. Fiete Haack, M.Sc. Philipp Henning

Thünen Institute for Baltic Sea Fisheries: M.Sc. Kevin Haase, Dr. Maria E.Pierce


Prof. Hans-Christian Jetter, Universität zu Lübeck : "Mensch-Daten-Interaktion und Transitional Interfaces"


Transitional Interfaces stellen eine zunehmend bedeutsame und bislang wenig erforschte Klasse von Benutzungsschnittstellen für die Mensch-Daten-Interaktion dar. Diese Benutzungsschnittstellen kombinieren die traditionelle Interaktion und Visualisierung mittels PCs, großen Touchscreens oder Mobilgeräten nahtlos mit Augmented und Virtual Reality. In Transitional Interfaces können zu jedem Zeitpunkt Mitglieder eines Teams individuell zwischen unterschiedlichen Positionen (bzw. "Kontexten") auf dem Realitäts-Virtualitäts-Kontinuum wechseln, um das für die aktuelle Aufgabe persönlich am besten geeignete Bedien- und Visualisierungskonzept zu wählen. Mein Vortrag wird zunächst den Begriff der "Mensch-Daten-Interaktion" bzw. Human-Data Interaction (HDI) vorstellen und welche Schlüsselrolle die menschliche Interaktion mit Visualisierungen dabei spielt. Dann werde ich die "Transitional Interfaces" als neues Forschungsthema innerhalb der HDI einführen, das verschiedene Aspekte der vorgenannten Themen in sich vereint.

Prof. Hans-Christian Jetter, Universität zu Lübeck

Hans-Christian Jetter ist Informatiker und Professor für Interaktionsdesign und User Experience an der Universität zu Lübeck. Er widmet sich in seiner Forschungsarbeit einer idealerweise "natürlichen" Mensch-Daten-Interaktion. Diese soll es Teams ermöglichen, auf möglichst einfache und effiziente Art komplexe Daten und Modelle gemeinsam zu explorieren, zu visualisieren und zu manipulieren - zum Beispiel unter Verwendung mobiler oder großer Touchscreens sowie Augmented oder Virtual Reality.  Während und nach seiner Promotion an der Universität Konstanz im Jahre 2013 forschte Hans-Christian Jetter bei Microsoft Research Cambridge und am University College London bis er 2015 einen Ruf an die Fachhochschule Oberösterreich, Campus Hagenberg annahm. Seit August 2020 ist er neuer Professor für Interaktionsdesign und User Experience an der Universität zu Lübeck, wo er unter anderem den Schwerpunkt Interaktions- und Mediendesign in den Bachelor- und Master-Studiengängen der Medieninformatik vertritt.


New staff members at the VAC presenting their work

M.Sc. Devesh Singh

Devesh Singh recently obtained his Master’s degree in Data and Knowledge Engineering from Otto-von-Guericke University Magdeburg. He now joined the DZNE Rostock as a PhD student working on deep learning explainability under the supervision of Dr. Martin Dyrba.

 In this VAC colloquium, he will present his two past projects:

  • The Data Science for Social Good (DSSG) Short Term Fellowship with DFKI and TU Kaiserslautern was a full-time summer fellowship program which trained data scientists to work on machine learning projects with social impact. Devesh was working with data from the Paraguayan national public procurement agency (Dirección Nacional de Contrataciones Públicas (DNCP)) to detect fraudulent public procurement processes which might be an indicator of corruption and other inconsistencies. He worked on training NLP models to automatically analyze the data. The realized explainable model was four times better than the DNCP’s existing process.
  • External Master Thesis at SICK Hamburg.
    SICK is a German manufacturing company whose industrial sensor solutions are used in logistical centers and large-scale warehouses. To further advance their existing image classification models, deep-learning based generative Image-to-Image (I2I) translation methods were explored under the larger setup of synthetic data generation. Devesh worked with two I2I approaches: CycleGANs and Contrastive Unpaired Translation (CUT). The realized I2I translation model was consistent with the semantic information given in the input images as well as it was able to produce textures from the desired target domain for the generated images. 

M.Sc. Samaneh Zolfaghari

Samaneh Zolfaghari is currently doing her last year of PhD in the Mathematics and Computer Science department of the University of Cagliari, Italy. She started her PhD in the Autumn of 2019 and her research concentration is on sensor-based behavior and locomotion monitoring for healthcare applications. 

She obtained her M.S. and B.S. in Computer Engineering (Software) from Alzahra University and Shahid Rajaee University in 2016, and 2013, respectively in Iran. Her research interests are smart environments, AI and machine learning applications in health care, and human factors in pervasive computing. Currently, she’s serving as a visiting scholar at the University of Rostock working on the kitchen task assessment dataset, in order to detect challenging behaviors in cooking activities performed by people with cognitive impairments. The challenge here is to identify the actions the person is executing, and the goals he/she is following, to detect errors in behavior, and to reason about the causes of these errors.


Prof. Chris J. Myers, University of Colorado Boulder (USA) : "Design of Asynchronous Genetic Circuits"


Researchers are now able to engineer synthetic genetic circuits for a range of applications in the environmental, medical, and energy domains. Crucial to the success of these efforts is the development of methods and tools for genetic design automation (GDA). While inspiration can be drawn from experiences with electronic design automation (EDA), design with a genetic material poses several challenges. In particular, genetic circuits are composed of very noisy components making their behavior more asynchronous, analog, and stochastic in nature. This talk presents our research in the development of GDA tools that leverage our past experiences in asynchronous circuit synthesis and formal verification. These tools enable synthetic biologists to construct models, efficiently analyze and visualize them, and synthesize a genetic circuit from a library of parts. Each step of this design process utilizes standard data representation formats enabling the ready exchange of results.

Prof. Chris J. Myers, University of Colorado Boulder

Chris J. Myers received a BS in EE and Chinese history from Caltech, and MSEE and PhD degrees from Stanford. Before becoming Chair of ECEE at CU Boulder in 2020, he was a professor and associate chair in ECE at the University of Utah. Myers is the author of over 200 technical papers and the textbooks Asynchronous Circuit Design and Engineering Genetic Circuits. He is also a co-inventor on four patents. His research interests include asynchronous design, formal verification, and genetic circuit design. Myers received an NSF Fellowship in 1991, an NSF CAREER award in 1996, best paper awards at the 1999 and 2007 Symposiums on Asynchronous Circuits and Systems, and is a fellow of the IEEE. He is a leader in the development of standards for systems and synthetic biology. In particular, he has served as an editor for the SBML standard, is the chair of the steering committee for the SBOL standard and is the past chair of the COMBINE coordination board.


Prof. Alessandro Pelligrini, University of Rome Tor Vergata (Italy) : "Runtime Systems for Fun and Profit"


Runtime systems are fundamental components of modern applications that provide the necessary support for executing programs and sometimes allow for advanced introspection capabilities. In this talk, I will provide an overview of recent and current research activities on runtime systems carried out by the High Performance and Dependable Computing Systems (HPDCS) research group at the University of Rome Tor Vergata. In the Software Engineering field, we show how a symbolic/concrete runtime environment allows behavioural similarity analysis, enabling effective test program prioritization and reducing the time-to-test. In High-Performance Computing, we show how a simple programming model allows for significant speedup of Discrete-Event Simulation models by relying on asynchronous/non-blocking algorithms. Similarly, we show that it is possible to improve the performance of task-based applications by explicitly addressing the detection of priority inversions of tasks. Concerning Cyber Security, we show how to carry out transparent system-wide detection of side-channel attacks leveraging off-the-shelf hardware components called Performance Monitoring Units. We also show how runtime environments could promote Anti-Tampering frameworks to make general applications harder to reverse engineer.

Prof. Alessandro Pelligrini, University of Rome Tor Vergata

Alessandro Pelligrini is an Assistant Professor at the University of Rome Tor Vergata in the School of Engineering. He received his PhD in Computer Engineering from Sapienza, University of Rome, in 2014. His research interests are high-performance computing, compilers, operating systems, large-scale simulation, cyber security and distributed and concurrent algorithms. In 2018 he won the HiPEAC Technology Transfer Award, while in 2015 he won the prize for the best PhD thesis of the year from Sapienza, University of Rome. He has worked as a researcher in many national/international research institutes, such as CNIT, ISSNOVA, CINI, CINFAI, IRIANC, and BSC.


Dr. Emma L. Tonkin, University of Bristol (UK) : "SPHERE -- Sensor Platform for HealthcarE in a Residential Environment: The Vision and The Lessons Learned"

It is a truism in healthcare to state that the process of diagnosis is extremely important to patient care, increasing the likelihood of a positive outcome for the patient. However, diagnosis depends on information availability, which depends on the availability of sensors capable of eliciting the information the clinician needs. Direct observation by a clinician is naturally a starting point, but clinician time is limited and expensive. The use of large diagnostic tools offers powerful insight, but do not represent a panacea. Both of these can only provide a snapshot in time, in large part because many aspects of the patient’s lived experience simply do not show up in the timescale observed. As a result, there is considerable interest in the effectiveness of relatively small, cheap sensors, such as wearable accelerometers, as an additional data source to support the processes of diagnosis and evaluation of treatment.

The SPHERE project has explored the possibility of making use of multiple small, cheap sensors in the home to describe participants’ everyday life, testing systems in well over sixty homes over several years. The project used data drawn from a heterogeneous sensor network to support the detection of information such as activities of daily living, sleep and personal hygiene.

In this seminar, we look at the strengths and limitations of single- and multi-sensor approaches. We explore the challenges of heterogeneous (multi-sensor) system deployment, and the many difficulties that are involved in deployment of complex sensor networks in participant homes, from the effect of architecture on signal reception and networking to the identification of minimally-invasive methods of fixing removable sensors in place. We discuss the issues involved in recruiting participants, particularly the need to sensitively negotiate participant acceptance of privacy-invasive technologies such as silhouette cameras during the design process, and to identify and adopt privacy-enhancing mechanisms wherever appropriate.

We then discuss the challenges of the deployment process, particularly system monitoring, reliability engineering and repair, with a focus on whole-cohort management using configuration management systems and the urgent need to develop COVID-safe system engineering methods to safeguard vulnerable populations. Finally, we discuss lessons learned from analysing multi-sensor pervasive healthcare data alongside subject-expert clinicians, and suggest some recommendations from our own experience.

Dr. Emma L. Tonkin, University of Bristol


Prof. Danny Weyns, Katholieke Universiteit Leuven ( Belgium), Linnaeus University (Sweden) : "Engineering Self-Adaptive Systems with Guarantees using ActivFORMS"


Self-adaptation equips a computing system with a feedback loop that enables it dealing with uncertainties during operation, such as sudden changes in the availability of resources or fluctuating workloads. One of the key challenges of engineering self-adaptive systems is ensuring that the system complies with the adaptation goals.  To that end, we defined ActivFORMS (Active FORmal Models for Self-adaptation). ActivFORMS spans four main stages of the life cycle of a feedback loop: design, deployment, runtime adaptation, and evolution. In this talk we give an overview of ActivFORMS and zoom in on one of its distinct features: the use of statistical model checking at runtime to select adaptation options that realise the adaptation goals with a required level of accuracy and confidence. We use an IoT application for building security monitoring that is deployed in Leuven as illustrative case. 

Prof. Danny Weyns, Katholieke Universiteit Leuven, Linnaeus University

Prof. Danny Weyns is a professor at the Katholieke Universiteit Leuven, Belgium; he is also affiliated with Linnaeus University in Sweden. The research of Danny’ team is centred on the engineering of self-adaptive systems. His particular focus is on achieving trustworthiness of self-adaptive systems that operate under uncertainty. To that end, he combines runtime models that represent uncertainty as first-class citizen with verification techniques at runtime in order to provide assurances for the required adaptation goals. Validation domains include service based systems, cyber-physical systems, and the Internet of Things. 


Dr. Niki Popper, TU Wien / dwh GmbH : "Datenbasis und Simulationsmodelle - notwendige Grundlagen für bessere Entscheidungen in der COVID19 Krise"


Die Covid-19 Pandemie hat EntscheidungsträgerInnen aus Politik und Gesundheitswesen vor beispiellose Herausforderungen gestellt. Primäres Ziel war und ist dabei die Grenzen der Gesundheitssysteme nicht zu überschreiten, um eine entsprechende Versorgung der Bevölkerung gewährleisten zu können. Aber mit zunehmendem Verlauf der Pandemie spielen auch andere Outcomes eine wichtige Rolle. Durch jahrelange Expertise und Forschung, in Kooperation mit der dwh GmbH und der TU Wien, verfügt die Forschungsplattform DEXHELPP über Werkzeuge (u.a. mit GEPOC und dem ABT-Framework), mit denen sowohl die Effizienz und Wirksamkeit einzelner Maßnahmen bzw. von Maßnahmenpaketen als auch deren Auswirkungen auf die zur Verfügung stehenden Ressourcen des Gesundheitssystems berechnet werden können. Der Vortrag "Datenbasis und Simulationsmodelle - notwendige Grundlagen für bessere Entscheidungen in der COVID19 Krise" wird dabei insbesondere auf die Rolle der Daten als Input, für die Kalibrierung und Validierung von Simulationsmodellen eingehen.

Weitere Informationen

Dr. Niki Popper, TU Wien / dwh GmbH

Dr. Niki Popper ist Mitglied in der Gesamtstaatlichen Covid-Krisenkoordination (Gecko) in Österreich und Leiter des DEXHELPP-Teams. Seine Gruppe ist seit März 2020 MItglied des von der Gesundheit Österreich GmbH koordinierten COVID-19 Prognosekonsortiums in Österreich, in dem in wöchenlichem Zyklus nicht nur öffentlich zugängliche Prognosen für Fallzahlen und Spitalskapazitäten erstellt werden, sondern auch ein wichtiger Diskurs unterschiedlicher österreichischen Modellierungsgruppen stattfindet, der zur regelmäßigen Verbesserung der Modelle beiträgt. Mit der Landesklinikenholding Niederösterreich und vormals dem Gesundheitsverbund Wien arbeitet seine Gruppe mit den wichtigsten Krankenanstaltenverbunden Ostösterreichs zusammen und berät/beriet diese mit Szenarienrechnungen im Hinblick auf Normal- und Intensivbett Belegszahlen. Darüber hinaus ist das Team an einer Reihe geförderter Forschungsprojekte beteiligt, um den Wissensstand in diesem wichtigen Bereich weiter auszubauen.


M.Sc. Christine Ripken, Breakpoint One GmbH Berlin : "Immersive Analytics of Heterogeneous Biological Data Informed through Need-finding Interviews"

The amount of biological data is continuously growing, the reason why the data analysis methods have to evolve accordingly. Throughout the project AVATARS various biological data about rapeseed such as genomes, transcriptomes, metabolomes, and phenomes are generated and visualized in virtual reality. Since all biological data domains are related, AVATARS aims to support a holistic understanding of several and complex data sets with immersive analytics.

In a first step, need-finding interviews were conducted to identify core and pressing data analysis needs of twelve biologists. Based on the insights, a first prototype has been developed. A tabular representation in VR is used to align genomes of several phenotypes. The prototype supports the user to get an overview of up to 5 million data values, to access details on demand and in real-time. Initial user feedback indicates that immersive analytics is beneficial to analyze large data sets.


Prof. Marian Dörk und M.A. Mark-Jan Bludau, Fachhochschule Potsdam : "Gestaltung und Entwicklung interaktiver Datenvisualisierungen am Beispiel kultureller Sammlungen"

Das übergeordnete Ziel unserer designorientierten Visualisierungsforschung ist es, grafische Benutzeroberflächen zu entwickeln, die die ergebnisoffene Erkundung komplexer Daten - z.B. des digitalen Kulturerbes - anregen. In unserem Vortrag stellen wir Konzepte, Methoden sowie Frage- und Zielstellungen vor, die hinter unserer Arbeit stehen.

Im ersten Teil gehen wir auf theoretische und praktische Herangehensweisen unserer Forschung in Potsdam ein. Philosophische Konzepte wie der Flaneur und die Falte können dabei helfen, lange bestehende Dichotomien wie die Unterscheidung zwischen Überblick und Detail oder die Trennung von Interaktion und Repräsentation zu hinterfragen. Zu unserem Methodenkanon zählen wir insbesondere das Co-Design, in dem für ein Projekt relevante Personen direkt in den Gestaltungs- und Forschungsprozess eingebunden werden. In diesem Modus können Konzepte für prototypische Interfaces und Visualisierungen entstehen, die umfassende Bestände wie Zeichnungen, Münzen, Handbibliotheken, Kunstsammlungen und Künstlernachlässe über zoombare, filterbare oder multiperspektivische Arrangements explorieren lassen.

Insbesondere in den Geisteswissenschaften führt die Visualisierung von Daten zu einer Reihe von Herausforderungen durch Dateneigenschaften wie Unsicherheit, Mehrdeutigkeit, Lokalität und Subjektivität. Diese Eigenschaften werden durch den Einsatz von statistischen und datenanalytischen Prozessen und Visualisierungsformen mit dem Ziel von Reduktion von Gesamtkomplexität häufig nicht ausreichend repräsentiert.

Im zweiten Teil des Vortrags geht es darauf aufbauend um die Erforschung von Interaktionen, Visualisierungen und animierten Übergängen zur Bewegung zwischen unterschiedlichen Abstraktions- und Granularitätsstufen von Daten. Im Bezug darauf wird die Forschungsfrage aufgeworfen, wie interaktiv situierte Detailerhöhung durch integrierte Visualisierungstechniken reichhaltigere, kontext-erhaltende Explorationserfahrungen ermöglichen kann.

Prof. Marian Dörk und M.A. Mark-Jan Bludau

Prof. Marian Dörk ist Forschungsprofessor am Fachbereich Design und Institut für angewandte Forschung Urbane Zukunft der Fachhochschule Potsdam. Seine Forschung und Lehre fokussieren sich auf Datenvisualisierung mit besonderer Sensibilität für soziale, kulturelle und technologische Transformationsprozesse. Er ist Co-Direktor des UCLAB, einer transdisziplinären Forschungsgruppe an der Schnittstelle zwischen Informatik, Design und Geisteswissenschaften.

Mark-Jan Bludau is a research associate at the Urban Complexity Lab (UCLAB) - interdisciplinary research group at Fachhochschule Potsdam. His main field of interest lies in information visualizations with special focus on cultural heritage data, interaction techniques and bridging and transitioning between multiple abstraction states.