TY - JOUR
A1 - Xu, Rudan
A1 - Razaghi-Moghadam, Zahra
A1 - Nikoloski, Zoran
T1 - Maximization of non-idle enzymes improves the coverage of the estimated maximal in vivo enzyme catalytic rates in Escherichia coli
JF - Bioinformatics
N2 - Motivation:
Constraint-based modeling approaches allow the estimation of maximal in vivo enzyme catalytic rates that can serve as proxies for enzyme turnover numbers. Yet, genome-scale flux profiling remains a challenge in deploying these approaches to catalogue proxies for enzyme catalytic rates across organisms.
Results:
Here, we formulate a constraint-based approach, termed NIDLE-flux, to estimate fluxes at a genome-scale level by using the principle of efficient usage of expressed enzymes. Using proteomics data from Escherichia coli, we show that the fluxes estimated by NIDLE-flux and the existing approaches are in excellent qualitative agreement (Pearson correlation > 0.9). We also find that the maximal in vivo catalytic rates estimated by NIDLE-flux exhibits a Pearson correlation of 0.74 with in vitro enzyme turnover numbers. However, NIDLE-flux results in a 1.4-fold increase in the size of the estimated maximal in vivo catalytic rates in comparison to the contenders. Integration of the maximum in vivo catalytic rates with publically available proteomics and metabolomics data provide a better match to fluxes estimated by NIDLE-flux. Therefore, NIDLE-flux facilitates more effective usage of proteomics data to estimate proxies for kcatomes.
Y1 - 2021
U6 - https://doi.org/10.1093/bioinformatics/btab575
SN - 1367-4803
SN - 1460-2059
VL - 37
IS - 21
SP - 3848
EP - 3855
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - THES
A1 - Wolf, Johannes
T1 - Analysis and visualization of transport infrastructure based on large-scale geospatial mobile mapping data
T1 - Analyse und Visualisierung von Verkehrsinfrastruktur basierend auf großen Mobile-Mapping-Datensätzen
N2 - 3D point clouds are a universal and discrete digital representation of three-dimensional objects and environments. For geospatial applications, 3D point clouds have become a fundamental type of raw data acquired and generated using various methods and techniques. In particular, 3D point clouds serve as raw data for creating digital twins of the built environment.
This thesis concentrates on the research and development of concepts, methods, and techniques for preprocessing, semantically enriching, analyzing, and visualizing 3D point clouds for applications around transport infrastructure. It introduces a collection of preprocessing techniques that aim to harmonize raw 3D point cloud data, such as point density reduction and scan profile detection. Metrics such as, e.g., local density, verticality, and planarity are calculated for later use. One of the key contributions tackles the problem of analyzing and deriving semantic information in 3D point clouds. Three different approaches are investigated: a geometric analysis, a machine learning approach operating on synthetically generated 2D images, and a machine learning approach operating on 3D point clouds without intermediate representation.
In the first application case, 2D image classification is applied and evaluated for mobile mapping data focusing on road networks to derive road marking vector data. The second application case investigates how 3D point clouds can be merged with ground-penetrating radar data for a combined visualization and to automatically identify atypical areas in the data. For example, the approach detects pavement regions with developing potholes. The third application case explores the combination of a 3D environment based on 3D point clouds with panoramic imagery to improve visual representation and the detection of 3D objects such as traffic signs.
The presented methods were implemented and tested based on software frameworks for 3D point clouds and 3D visualization. In particular, modules for metric computation, classification procedures, and visualization techniques were integrated into a modular pipeline-based C++ research framework for geospatial data processing, extended by Python machine learning scripts. All visualization and analysis techniques scale to large real-world datasets such as road networks of entire cities or railroad networks.
The thesis shows that some use cases allow taking advantage of established image vision methods to analyze images rendered from mobile mapping data efficiently. The two presented semantic classification methods working directly on 3D point clouds are use case independent and show similar overall accuracy when compared to each other. While the geometry-based method requires less computation time, the machine learning-based method supports arbitrary semantic classes but requires training the network with ground truth data. Both methods can be used in combination to gradually build this ground truth with manual corrections via a respective annotation tool.
This thesis contributes results for IT system engineering of applications, systems, and services that require spatial digital twins of transport infrastructure such as road networks and railroad networks based on 3D point clouds as raw data. It demonstrates the feasibility of fully automated data flows that map captured 3D point clouds to semantically classified models. This provides a key component for seamlessly integrated spatial digital twins in IT solutions that require up-to-date, object-based, and semantically enriched information about the built environment.
N2 - 3D-Punktwolken sind eine universelle und diskrete digitale Darstellung von dreidimensionalen Objekten und Umgebungen. Für raumbezogene Anwendungen sind 3D-Punktwolken zu einer grundlegenden Form von Rohdaten geworden, die mit verschiedenen Methoden und Techniken erfasst und erzeugt werden. Insbesondere dienen 3D-Punktwolken als Rohdaten für die Erstellung digitaler Zwillinge der bebauten Umwelt.
Diese Arbeit konzentriert sich auf die Erforschung und Entwicklung von Konzepten, Methoden und Techniken zur Vorverarbeitung, semantischen Anreicherung, Analyse und Visualisierung von 3D-Punktwolken für Anwendungen im Bereich der Verkehrsinfrastruktur. Es wird eine Sammlung von Vorverarbeitungstechniken vorgestellt, die auf die Harmonisierung von 3D-Punktwolken-Rohdaten abzielen, so z.B. die Reduzierung der Punktdichte und die Erkennung von Scanprofilen. Metriken wie bspw. die lokale Dichte, Vertikalität und Planarität werden zur späteren Verwendung berechnet. Einer der Hauptbeiträge befasst sich mit dem Problem der Analyse und Ableitung semantischer Informationen in 3D-Punktwolken. Es werden drei verschiedene Ansätze untersucht: Eine geometrische Analyse sowie zwei maschinelle Lernansätze, die auf synthetisch erzeugten 2D-Bildern, bzw. auf 3D-Punktwolken ohne Zwischenrepräsentation arbeiten.
Im ersten Anwendungsfall wird die 2D-Bildklassifikation für Mobile-Mapping-Daten mit Fokus auf Straßennetze angewendet und evaluiert, um Vektordaten für Straßenmarkierungen abzuleiten. Im zweiten Anwendungsfall wird untersucht, wie 3D-Punktwolken mit Bodenradardaten für eine kombinierte Visualisierung und automatische Identifikation atypischer Bereiche in den Daten zusammengeführt werden können. Der Ansatz erkennt zum Beispiel Fahrbahnbereiche mit entstehenden Schlaglöchern. Der dritte Anwendungsfall untersucht die Kombination einer 3D-Umgebung auf Basis von 3D-Punktwolken mit Panoramabildern, um die visuelle Darstellung und die Erkennung von 3D-Objekten wie Verkehrszeichen zu verbessern.
Die vorgestellten Methoden wurden auf Basis von Software-Frameworks für 3D-Punktwolken und 3D-Visualisierung implementiert und getestet. Insbesondere wurden Module für Metrikberechnungen, Klassifikationsverfahren und Visualisierungstechniken in ein modulares, pipelinebasiertes C++-Forschungsframework für die Geodatenverarbeitung integriert, das durch Python-Skripte für maschinelles Lernen erweitert wurde. Alle Visualisierungs- und Analysetechniken skalieren auf große reale Datensätze wie Straßennetze ganzer Städte oder Eisenbahnnetze.
Die Arbeit zeigt, dass es in einigen Anwendungsfällen möglich ist, die Vorteile etablierter Bildverarbeitungsmethoden zu nutzen, um aus Mobile-Mapping-Daten gerenderte Bilder effizient zu analysieren. Die beiden vorgestellten semantischen Klassifikationsverfahren, die direkt auf 3D-Punktwolken arbeiten, sind anwendungsfallunabhängig und zeigen im Vergleich zueinander eine ähnliche Gesamtgenauigkeit. Während die geometriebasierte Methode weniger Rechenzeit benötigt, unterstützt die auf maschinellem Lernen basierende Methode beliebige semantische Klassen, erfordert aber das Trainieren des Netzwerks mit Ground-Truth-Daten. Beide Methoden können in Kombination verwendet werden, um diese Ground Truth mit manuellen Korrekturen über ein entsprechendes Annotationstool schrittweise aufzubauen.
Diese Arbeit liefert Ergebnisse für das IT-System-Engineering von Anwendungen, Systemen und Diensten, die räumliche digitale Zwillinge von Verkehrsinfrastruktur wie Straßen- und Schienennetzen auf der Basis von 3D-Punktwolken als Rohdaten benötigen. Sie demonstriert die Machbarkeit von vollautomatisierten Datenflüssen, die erfasste 3D-Punktwolken auf semantisch klassifizierte Modelle abbilden. Dies stellt eine Schlüsselkomponente für nahtlos integrierte räumliche digitale Zwillinge in IT-Lösungen dar, die aktuelle, objektbasierte und semantisch angereicherte Informationen über die bebaute Umwelt benötigen.
KW - 3D point cloud
KW - geospatial data
KW - mobile mapping
KW - semantic classification
KW - 3D visualization
KW - 3D-Punktwolke
KW - räumliche Geodaten
KW - Mobile Mapping
KW - semantische Klassifizierung
KW - 3D-Visualisierung
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-536129
ER -
TY - THES
A1 - Weise, Matthias
T1 - Auswahl von Selektions- und Manipulationstechniken für Virtual Reality-Anwendungen
T1 - Choosing selection and manipulation techniques for Virtual Reality applications
N2 - Die stetige Weiterentwicklung von VR-Systemen bietet neue Möglichkeiten der Interaktion mit virtuellen Objekten im dreidimensionalen Raum, stellt Entwickelnde von VRAnwendungen aber auch vor neue Herausforderungen. Selektions- und Manipulationstechniken müssen unter Berücksichtigung des Anwendungsszenarios, der Zielgruppe und der zur Verfügung stehenden Ein- und Ausgabegeräte ausgewählt werden. Diese Arbeit leistet einen Beitrag dazu, die Auswahl von passenden Interaktionstechniken zu unterstützen. Hierfür wurde eine repräsentative Menge von Selektions- und Manipulationstechniken untersucht und, unter Berücksichtigung existierender Klassifikationssysteme, eine Taxonomie entwickelt, die die Analyse der Techniken hinsichtlich interaktionsrelevanter Eigenschaften ermöglicht. Auf Basis dieser Taxonomie wurden Techniken ausgewählt, die in einer explorativen Studie verglichen wurden, um Rückschlüsse auf die Dimensionen der Taxonomie zu ziehen und neue Indizien für Vor- und Nachteile der Techniken in spezifischen Anwendungsszenarien zu generieren. Die Ergebnisse der Arbeit münden in eine Webanwendung, die Entwickelnde von VR-Anwendungen gezielt dabei unterstützt, passende Selektions- und Manipulationstechniken für ein Anwendungsszenario auszuwählen, indem Techniken auf Basis der Taxonomie gefiltert und unter Verwendung der Resultate aus der Studie sortiert werden können.
N2 - The constant advancement of VR systems offers new possibilities of interaction with virtual objects in three-dimensional space, but also poses new challenges for developers of VR applications. Selection and manipulation techniques have to be chosen in dependence of the application scenario, the users and the available input and output devices. This work contributes to support the selection of suitable interaction techniques. A representative quantity of selection and manipulation techniques has been investigated and a taxonomy has been developed based on existing classification systems which allows the analysis of the techniques with respect to properties relevant for interaction. Based on this taxonomy, techniques were selected and compared in an exploratory study in order to draw conclusions about the dimensions of the taxonomy and to generate new evidence for advantages and disadvantages of the techniques in specific application scenarios. The results of the work lead to a web application, which supports the developer of VR applications in choosing suitable selection and manipulation techniques for an application scenario by filtering techniques based on the taxonomy and sorting them using the results of the study.
KW - Virtual Reality
KW - Interaktionstechniken
KW - Mensch-Computer-Interaktion
KW - Virtual Reality
KW - interaction techniques
KW - human computer interaction
Y1 - 2022
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-534586
ER -
TY - JOUR
A1 - von Steinau-Steinrück, Robert
A1 - Jöris, Nils
T1 - Brexit-Arbeitsrecht und die Folgen
JF - NJW spezial
N2 - Die Corona-Pandemie hat den Brexit ein wenig in den Hintergrund gedrängt. Dabei hat er gerade im Arbeitsrecht ganz erhebliche Auswirkungen. Über sie geben wir einen Überblick.
Y1 - 2021
UR - https://beck-online.beck.de/Bcid/Y-300-Z-NJW-SPEZIAL-B-2021-S-242-N-1
SN - 1613-4621
VL - 18
IS - 8
SP - 242
EP - 243
PB - C.H. Beck
CY - München
ER -
TY - JOUR
A1 - von Steinau-Steinrück, Robert
A1 - Bruhn, Emma
T1 - Der Impfmuffel im Arbeitsrecht
JF - NJW spezial
N2 - Trotz erfolgreicher Impfkampagne droht nach dem Sommer eine vierte Infektionswelle der Corona-Pandemie. Ob es dazu kommen wird, hängt maßgeblich davon ab, wie viele Menschen sich für eine Corona-Schutzimpfung entscheiden. Am Impfstoff mangelt es nicht mehr, dafür an der Impfbereitschaft. Viele Arbeitgeber fragen sich daher, was sie unternehmen können, um die Impfquote in ihren Betrieben zu erhöhen.
Y1 - 2021
UR - https://beck-online.beck.de/Bcid/Y-300-Z-NJW-SPEZIAL-B-2021-S-498-N-1
SN - 1613-4621
VL - 18
IS - 16
SP - 498
EP - 499
PB - C.H. Beck
CY - München
ER -
TY - JOUR
A1 - von Steinau-Steinrück, Robert
T1 - Was ist bei "Workation" und "Bleisure" rechtlich zu beachten?
JF - NJW spezial
N2 - Die Digitalisierung unseres Lebens löst die Grenzen zwischen Privat- und Berufsleben immer weiter auf. Bekanntes Beispiel ist das Homeoffice. Arbeitgeber begegnen aber auch zahlreichen weiteren Trends in diesem Zusammenhang. Dazu gehören „workation“, also die Verbindung zwischen Arbeit („work“) und Urlaub („vacation“) ebenso wie „bleisure“, dh die Verbindung von Dienstreisen („business“) und Urlaub („leisure“). Der Beitrag geht den rechtlichen Rahmenbedingungen hierfür nach.
Y1 - 2021
UR - https://beck-online.beck.de/Bcid/Y-300-Z-NJW-SPEZIAL-B-2021-S-626-N-1
SN - 1613-4621
VL - 18
IS - 20
SP - 626
EP - 627
PB - C.H. Beck
CY - München
ER -
TY - JOUR
A1 - Vitagliano, Gerardo
A1 - Jiang, Lan
A1 - Naumann, Felix
T1 - Detecting layout templates in complex multiregion files
JF - Proceedings of the VLDB Endowment
N2 - Spreadsheets are among the most commonly used file formats for data management, distribution, and analysis. Their widespread employment makes it easy to gather large collections of data, but their flexible canvas-based structure makes automated analysis difficult without heavy preparation. One of the common problems that practitioners face is the presence of multiple, independent regions in a single spreadsheet, possibly separated by repeated empty cells. We define such files as "multiregion" files. In collections of various spreadsheets, we can observe that some share the same layout. We present the Mondrian approach to automatically identify layout templates across multiple files and systematically extract the corresponding regions. Our approach is composed of three phases: first, each file is rendered as an image and inspected for elements that could form regions; then, using a clustering algorithm, the identified elements are grouped to form regions; finally, every file layout is represented as a graph and compared with others to find layout templates. We compare our method to state-of-the-art table recognition algorithms on two corpora of real-world enterprise spreadsheets. Our approach shows the best performances in detecting reliable region boundaries within each file and can correctly identify recurring layouts across files.
Y1 - 2022
U6 - https://doi.org/10.14778/3494124.3494145
SN - 2150-8097
VL - 15
IS - 3
SP - 646
EP - 658
PB - Association for Computing Machinery
CY - New York
ER -
TY - JOUR
A1 - Ullrich, André
A1 - Teichmann, Malte
A1 - Gronau, Norbert
T1 - Fast trainable capabilities in software engineering-skill development in learning factories
JF - Ji suan ji jiao yu = Computer Education / Qing hua da xue
N2 - The increasing demand for software engineers cannot completely be fulfilled by university education and conventional training approaches due to limited capacities. Accordingly, an alternative approach is necessary where potential software engineers are being educated in software engineering skills using new methods. We suggest micro tasks combined with theoretical lessons to overcome existing skill deficits and acquire fast trainable capabilities. This paper addresses the gap between demand and supply of software engineers by introducing an actionoriented and scenario-based didactical approach, which enables non-computer scientists to code. Therein, the learning content is provided in small tasks and embedded in learning factory scenarios. Therefore, different requirements for software engineers from the market side and from an academic viewpoint are analyzed and synthesized into an integrated, yet condensed skills catalogue. This enables the development of training and education units that focus on the most important skills demanded on the market. To achieve this objective, individual learning scenarios are developed. Of course, proper basic skills in coding cannot be learned over night but software programming is also no sorcery.
KW - learning factory
KW - programming skills
KW - software engineering
KW - training
Y1 - 2021
U6 - https://doi.org/10.16512/j.cnki.jsjjy.2020.12.002
SN - 1672-5913
IS - 12
SP - 2
EP - 10
PB - [Verlag nicht ermittelbar]
CY - Bei jing shi
ER -
TY - JOUR
A1 - Trautmann, Justin
A1 - Zhou, Lin
A1 - Brahms, Clemens Markus
A1 - Tunca, Can
A1 - Ersoy, Cem
A1 - Granacher, Urs
A1 - Arnrich, Bert
T1 - TRIPOD
BT - A treadmill walking dataset with IMU, pressure-distribution and photoelectric data for gait analysis
JF - Data : open access ʻData in scienceʼ journal
N2 - Inertial measurement units (IMUs) enable easy to operate and low-cost data recording for gait analysis. When combined with treadmill walking, a large number of steps can be collected in a controlled environment without the need of a dedicated gait analysis laboratory. In order to evaluate existing and novel IMU-based gait analysis algorithms for treadmill walking, a reference dataset that includes IMU data as well as reliable ground truth measurements for multiple participants and walking speeds is needed. This article provides a reference dataset consisting of 15 healthy young adults who walked on a treadmill at three different speeds. Data were acquired using seven IMUs placed on the lower body, two different reference systems (Zebris FDMT-HQ and OptoGait), and two RGB cameras. Additionally, in order to validate an existing IMU-based gait analysis algorithm using the dataset, an adaptable modular data analysis pipeline was built. Our results show agreement between the pressure-sensitive Zebris and the photoelectric OptoGait system (r = 0.99), demonstrating the quality of our reference data. As a use case, the performance of an algorithm originally designed for overground walking was tested on treadmill data using the data pipeline. The accuracy of stride length and stride time estimations was comparable to that reported in other studies with overground data, indicating that the algorithm is equally applicable to treadmill data. The Python source code of the data pipeline is publicly available, and the dataset will be provided by the authors upon request, enabling future evaluations of IMU gait analysis algorithms without the need of recording new data.
KW - inertial measurement unit
KW - gait analysis algorithm
KW - OptoGait
KW - Zebris
KW - data pipeline
KW - public dataset
Y1 - 2021
U6 - https://doi.org/10.3390/data6090095
SN - 2306-5729
VL - 6
IS - 9
PB - MDPI
CY - Basel
ER -
TY - THES
A1 - Torcato Mordido, Gonçalo Filipe
T1 - Diversification, compression, and evaluation methods for generative adversarial networks
N2 - Generative adversarial networks (GANs) have been broadly applied to a wide range of application domains since their proposal. In this thesis, we propose several methods that aim to tackle different existing problems in GANs. Particularly, even though GANs are generally able to generate high-quality samples, the diversity of the generated set is often sub-optimal. Moreover, the common increase of the number of models in the original GANs framework, as well as their architectural sizes, introduces additional costs. Additionally, even though challenging, the proper evaluation of a generated set is an important direction to ultimately improve the generation process in GANs. We start by introducing two diversification methods that extend the original GANs framework to multiple adversaries to stimulate sample diversity in a generated set. Then, we introduce a new post-training compression method based on Monte Carlo methods and importance sampling to quantize and prune the weights and activations of pre-trained neural networks without any additional training. The previous method may be used to reduce the memory and computational costs introduced by increasing the number of models in the original GANs framework. Moreover, we use a similar procedure to quantize and prune gradients during training, which also reduces the communication costs between different workers in a distributed training setting. We introduce several topology-based evaluation methods to assess data generation in different settings, namely image generation and language generation. Our methods retrieve both single-valued and double-valued metrics, which, given a real set, may be used to broadly assess a generated set or separately evaluate sample quality and sample diversity, respectively. Moreover, two of our metrics use locality-sensitive hashing to accurately assess the generated sets of highly compressed GANs. The analysis of the compression effects in GANs paves the way for their efficient employment in real-world applications. Given their general applicability, the methods proposed in this thesis may be extended beyond the context of GANs. Hence, they may be generally applied to enhance existing neural networks and, in particular, generative frameworks.
N2 - Generative adversarial networks (GANs) wurden seit ihrer Einführung in einer Vielzahl von Anwendungsbereichen eingesetzt. In dieser Dissertation schlagen wir einige Verfahren vor, die darauf abzielen, verschiedene bestehende Probleme von GANs zu lösen. Insbesondere, fokussieren wir uns auf das Problem das GANs zwar qualitative hochwertige Samples generieren können, aber die Diversität ist oft sub-optimal. Darüber hinaus, stellt die allgemein übliche Zunahme der Anzahl der Modelle unter dem ursprünglichen GAN-Framework, als auch deren Modellgröße weitere Aufwendungskosten dar. Abschließend, ist die richtige Evaluierung einer generierten Menge, wenn auch herausfordernd, eine wichtige Forschungsrichtung, um letztendlich den Generierungsprozess von GANs zu verbessern.
Wir beginnen mit der Einführung von zwei Diversifizierungsmethoden die das ursprüngliche GAN-Framework um mehrere Gegenspieler erweitern, um die Diversität zu erhöhen. Um den zusätzlichen Speicher- und Rechenaufwand zu reduzieren, führen wir dann eine neue Kompressionsmethode ein. Diese Methode basiert auf den Monte-Carlo-Methoden und Importance Sampling, für das Quantisieren und Pruning der Gewichte und Aktivierungen von schon trainierten neuronalen Netzwerken ohne zusätzliches Trainieren. Wir erweitern die erwähne Methode zusätzlich für das Quantisieren und Pruning von Gradienten während des Trainierens, was die Kommunikationskosten zwischen verschiedenen sogenannten „Workern“ in einer verteilten Trainingsumgebung reduziert.
Bezüglich der Bewertung der generierten Samples, stellen wir mehrere typologie basierte Evaluationsmethoden vor, die sich auf Bild-und Text konzentrieren. Um verschiedene Anwendungsfälle zu erfassen, liefern unsere vorgestellten Methoden einwertige und doppelwertige Metriken. Diese können einerseits dazu genutzt werden, generierte Samples, oder die Qualität und Verteilung der Samples anhand einer Menge von echten Samples zu bewerten. Außerdem, verwenden zwei unserer vorgestellten Metriken so genanntes locality-sensitive Hashing, um die generierten Samples von stark komprimierten GANs genau zu bewerten. Die Analyse von Kompressionseffekten in GANs ebnet den Weg für ihren effizienten Einsatz für reale Anwendungen.
Aufgrund der allgemeinen Anwendungsmöglichkeit von GANs, können die in dieser Arbeit vorgestellten Methoden auch über Kontext von GANs hinaus erweitert werden. Daher könnten sie allgemein auf existierende neuronale Netzwerke angewandt werden und insbesondere auf generative Frameworks.
KW - deep learning
KW - generative adversarial networks
KW - erzeugende gegnerische Netzwerke
KW - tiefes Lernen
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-535460
ER -
TY - JOUR
A1 - Tavakoli, Hamad
A1 - Alirezazadeh, Pendar
A1 - Hedayatipour, Ava
A1 - Nasib, A. H. Banijamali
A1 - Landwehr, Niels
T1 - Leaf image-based classification of some common bean cultivars using discriminative convolutional neural networks
JF - Computers and electronics in agriculture : COMPAG online ; an international journal
N2 - In recent years, many efforts have been made to apply image processing techniques for plant leaf identification. However, categorizing leaf images at the cultivar/variety level, because of the very low inter-class variability, is still a challenging task. In this research, we propose an automatic discriminative method based on convolutional neural networks (CNNs) for classifying 12 different cultivars of common beans that belong to three various species. We show that employing advanced loss functions, such as Additive Angular Margin Loss and Large Margin Cosine Loss, instead of the standard softmax loss function for the classification can yield better discrimination between classes and thereby mitigate the problem of low inter-class variability. The method was evaluated by classifying species (level I), cultivars from the same species (level II), and cultivars from different species (level III), based on images from the leaf foreside and backside. The results indicate that the performance of the classification algorithm on the leaf backside image dataset is superior. The maximum mean classification accuracies of 95.86, 91.37 and 86.87% were obtained at the levels I, II and III, respectively. The proposed method outperforms the previous relevant works and provides a reliable approach for plant cultivars identification.
KW - Bean
KW - Plant identification
KW - Digital image analysis
KW - VGG16
KW - Loss
KW - functions
Y1 - 2021
U6 - https://doi.org/10.1016/j.compag.2020.105935
SN - 0168-1699
SN - 1872-7107
VL - 181
PB - Elsevier
CY - Amsterdam [u.a.]
ER -
TY - JOUR
A1 - Steinrötter, Björn
T1 - Das Konzept einer datenaltruistischen Organisation
JF - Datenschutz und Datensicherheit
N2 - Dass Technologien wie Machine Learning-Anwendungen oder Big bzw. Smart Data- Verfahren unbedingt Daten in ausreichender Menge und Güte benötigen, erscheint inzwischen als Binsenweisheit. Vor diesem Hintergrund hat insbesondere der EU-Gesetzgeber für sich zuletzt ein neues Betätigungsfeld entdeckt, indem er versucht, auf unterschiedlichen Wegen Anreize zum Datenteilen zu schaffen, um Innovation zu kreieren. Hierzu zählt auch eine geradezu wohltönend mit ,,Datenaltruismus‘‘ verschlagwortete Konstellation. Der Beitrag stellt die diesbezüglichen Regulierungserwägungen auf supranationaler Ebene dar und nimmt eine erste Analyse vor.
KW - coding and information theory
KW - computer science
KW - general
KW - cryptology
KW - data structures and information theory
Y1 - 2021
U6 - https://doi.org/10.1007/s11623-021-1539-6
SN - 1862-2607
SN - 1614-0702
VL - 45
IS - 12
SP - 794
EP - 798
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Shekhar, Sumit
A1 - Reimann, Max
A1 - Mayer, Maximilian
A1 - Semmo, Amir
A1 - Pasewaldt, Sebastian
A1 - Döllner, Jürgen
A1 - Trapp, Matthias
T1 - Interactive photo editing on smartphones via intrinsic decomposition
JF - Computer graphics forum : journal of the European Association for Computer Graphics
N2 - Intrinsic decomposition refers to the problem of estimating scene characteristics, such as albedo and shading, when one view or multiple views of a scene are provided. The inverse problem setting, where multiple unknowns are solved given a single known pixel-value, is highly under-constrained. When provided with correlating image and depth data, intrinsic scene decomposition can be facilitated using depth-based priors, which nowadays is easy to acquire with high-end smartphones by utilizing their depth sensors. In this work, we present a system for intrinsic decomposition of RGB-D images on smartphones and the algorithmic as well as design choices therein. Unlike state-of-the-art methods that assume only diffuse reflectance, we consider both diffuse and specular pixels. For this purpose, we present a novel specularity extraction algorithm based on a multi-scale intensity decomposition and chroma inpainting. At this, the diffuse component is further decomposed into albedo and shading components. We use an inertial proximal algorithm for non-convex optimization (iPiano) to ensure albedo sparsity. Our GPU-based visual processing is implemented on iOS via the Metal API and enables interactive performance on an iPhone 11 Pro. Further, a qualitative evaluation shows that we are able to obtain high-quality outputs. Furthermore, our proposed approach for specularity removal outperforms state-of-the-art approaches for real-world images, while our albedo and shading layer decomposition is faster than the prior work at a comparable output quality. Manifold applications such as recoloring, retexturing, relighting, appearance editing, and stylization are shown, each using the intrinsic layers obtained with our method and/or the corresponding depth data.
KW - CCS Concepts
KW - center dot Computing
KW - methodologie
KW - Image-based rendering
KW - Image
KW - processing
KW - Computational photography
Y1 - 2021
U6 - https://doi.org/10.1111/cgf.142650
SN - 0167-7055
SN - 1467-8659
VL - 40
SP - 497
EP - 510
PB - Blackwell
CY - Oxford
ER -
TY - BOOK
A1 - Seitz, Klara
A1 - Lincke, Jens
A1 - Rein, Patrick
A1 - Hirschfeld, Robert
T1 - Language and tool support for 3D crochet patterns
BT - virtual crochet with a graph structure
N2 - Crochet is a popular handcraft all over the world. While other techniques such as knitting or weaving have received technical support over the years through machines, crochet is still a purely manual craft. Not just the act of crochet itself is manual but also the process of creating instructions for new crochet patterns, which is barely supported by domain specific digital solutions. This leads to unstructured and often also ambiguous and erroneous pattern instructions. In this report, we propose a concept to digitally represent crochet patterns. This format incorporates crochet techniques which allows domain specific support for crochet pattern designers during the pattern creation and instruction writing process. As contributions, we present a thorough domain analysis, the concept of a graph structure used as domain specific language to specify crochet patterns and a prototype of a projectional editor using the graph as representation format of patterns and a diagramming system to visualize them in 2D and 3D. By analyzing the domain, we learned about crochet techniques and pain points of designers in their pattern creation workflow. These insights are the basis on which we defined the pattern representation. In order to evaluate our concept, we built a prototype by which the feasibility of the concept is shown and we tested the software with professional crochet designers who approved of the concept.
N2 - Häkeln ist eine weltweit verbreitete Handarbeitskunst. Obwohl andere Techniken, wie stricken und weben über die Zeit maschinelle Unterstützung erhalten haben, ist Häkeln noch heute ein komplett manueller Vorgang. Nicht nur das Häkeln an sich, sondern auch der Prozess zur Anleitungserstellung von neuen Häkeldesigns ist kaum unterstützt mit digitalen Lösungen. In dieser Arbeit stellen wir ein Konzept vor, das Häkelanleitungen digital repräsentiert. Das entwickelte Format integriert Häkeltechniken, wodurch wir den Prozess des Anleitungschreibens für Designer spezifisch für die Häkeldomäne unterstützen können. Als Beiträge analysieren wir umfassend die Häkeldomäne, entwickeln ein Konzept zur Repräsentation von Häkelanleitungen basierend auf einer Graphenstruktur als domänenspezifische Sprache und implementieren einen projektionalen Editor, der auf der besagten Graphenstruktur aufbaut und weiterhin die erstellten Anleitungen als schematische Darstellung in 2D und 3D visualisiert. Durch die Analyse der Domäne lernen wir Häkeltechniken und Schwachstellen beim Ablauf des Anleitungserstellens kennen. Basierend auf diesen Erkenntnissen entwickeln wir das digitale Format, um Anleitungen zu repräsentieren. Für die Evaluierung unseres Konzepts, haben wir einen Prototypen implementiert, der die Machbarkeit demonstriert. Zudem haben wir die Software von professionellen Häkeldesignern testen lassen, die unsere Herangehensweise gutheißen.
T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 137
KW - crochet
KW - visual language
KW - tools
KW - computer-aided design
KW - Häkeln
KW - visuelle Sprache
KW - Werkzeuge
KW - rechnerunterstütztes Konstruieren
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-492530
SN - 978-3-86956-505-7
SN - 1613-5652
SN - 2191-1665
IS - 137
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Schäfer, Robin
A1 - Stede, Manfred
T1 - Argument mining on twitter
BT - a survey
JF - Information technology : it ; Methoden und innovative Anwendungen der Informatik und Informationstechnik ; Organ der Fachbereiche 3 und 4 der GI e.V. und des Fachbereichs 6 der ITG
N2 - In the last decade, the field of argument mining has grown notably. However, only relatively few studies have investigated argumentation in social media and specifically on Twitter. Here, we provide the, to our knowledge, first critical in-depth survey of the state of the art in tweet-based argument mining. We discuss approaches to modelling the structure of arguments in the context of tweet corpus annotation, and we review current progress in the task of detecting argument components and their relations in tweets. We also survey the intersection of argument mining and stance detection, before we conclude with an outlook.
KW - Argument Mining
KW - Twitter
KW - Stance Detection
Y1 - 2021
U6 - https://doi.org/10.1515/itit-2020-0053
SN - 1611-2776
SN - 2196-7032
VL - 63
IS - 1
SP - 45
EP - 58
PB - De Gruyter
CY - Berlin
ER -
TY - BOOK
A1 - Schneider, Sven
A1 - Maximova, Maria
A1 - Giese, Holger
T1 - Probabilistic metric temporal graph logic
N2 - Cyber-physical systems often encompass complex concurrent behavior with timing constraints and probabilistic failures on demand. The analysis whether such systems with probabilistic timed behavior adhere to a given specification is essential. When the states of the system can be represented by graphs, the rule-based formalism of Probabilistic Timed Graph Transformation Systems (PTGTSs) can be used to suitably capture structure dynamics as well as probabilistic and timed behavior of the system. The model checking support for PTGTSs w.r.t. properties specified using Probabilistic Timed Computation Tree Logic (PTCTL) has been already presented. Moreover, for timed graph-based runtime monitoring, Metric Temporal Graph Logic (MTGL) has been developed for stating metric temporal properties on identified subgraphs and their structural changes over time. In this paper, we (a) extend MTGL to the Probabilistic Metric Temporal Graph Logic (PMTGL) by allowing for the specification of probabilistic properties, (b) adapt our MTGL satisfaction checking approach to PTGTSs, and (c) combine the approaches for PTCTL model checking and MTGL satisfaction checking to obtain a Bounded Model Checking (BMC) approach for PMTGL. In our evaluation, we apply an implementation of our BMC approach in AutoGraph to a running example.
N2 - Cyber-physische Systeme umfassen häufig ein komplexes nebenläufiges Verhalten mit Zeitbeschränkungen und probabilistischen Fehlern auf Anforderung. Die Analyse, ob solche Systeme mit probabilistischem gezeitetem Verhalten einer vorgegebenen Spezifikation entsprechen, ist essentiell. Wenn die Zustände des Systems durch Graphen dargestellt werden können, kann der regelbasierte Formalismus von probabilistischen gezeiteten Graphtransformationssystemen (PTGTSs) verwendet werden, um die Strukturdynamik sowie das probabilistische und gezeitete Verhalten des Systems geeignet zu erfassen. Die Modellprüfungsunterstützung für PTGTSs bzgl. Eigenschaften, die unter Verwendung von probabilistischer zeitgesteuerter Berechnungsbaumlogik (PTCTL) spezifiziert wurden, wurde bereits entwickelt. Darüber hinaus wurde das gezeitete graphenbasierte Laufzeitmonitoring mittels metrischer temporaler Graphlogik (MTGL) entwickelt, um metrische temporale Eigenschaften auf identifizierten Untergraphen und ihre strukturellen Änderungen über die Zeit zu erfassen.
In diesem Artikel (a) erweitern wir MTGL auf die probabilistische metrische temporale Graphlogik (PMTGL), indem wir die Spezifikation probabilistischer Eigenschaften zulassen, (b) passen unseren MTGL-Prüfungsansatz auf PTGTSs an und (c) kombinieren die Ansätze für PTCTL-Modellprüfung und MTGL-Prüfung, um einen beschränkten Modellprüfungsansatz (BMC-Ansatz) für PMTGL zu erhalten. In unserer Auswertung wenden wir eine Implementierung unseres BMC-Ansatzes in AutoGraph auf ein Beispiel an.
T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 140
KW - cyber-physische Systeme
KW - probabilistische gezeitete Systeme
KW - qualitative Analyse
KW - quantitative Analyse
KW - Bounded Model Checking
KW - cyber-physical systems
KW - probabilistic timed systems
KW - qualitative analysis
KW - quantitative analysis
KW - bounded model checking
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-515066
SN - 978-3-86956-517-0
SN - 1613-5652
SN - 2191-1665
IS - 140
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Schneider, Sven
A1 - Lambers, Leen
A1 - Orejas, Fernando
T1 - A logic-based incremental approach to graph repair featuring delta preservation
JF - International journal on software tools for technology transfer : STTT
N2 - We introduce a logic-based incremental approach to graph repair, generating a sound and complete (upon termination) overview of least-changing graph repairs from which a user may select a graph repair based on non-formalized further requirements. This incremental approach features delta preservation as it allows to restrict the generation of graph repairs to delta-preserving graph repairs, which do not revert the additions and deletions of the most recent consistency-violating graph update. We specify consistency of graphs using the logic of nested graph conditions, which is equivalent to first-order logic on graphs. Technically, the incremental approach encodes if and how the graph under repair satisfies a graph condition using the novel data structure of satisfaction trees, which are adapted incrementally according to the graph updates applied. In addition to the incremental approach, we also present two state-based graph repair algorithms, which restore consistency of a graph independent of the most recent graph update and which generate additional graph repairs using a global perspective on the graph under repair. We evaluate the developed algorithms using our prototypical implementation in the tool AutoGraph and illustrate our incremental approach using a case study from the graph database domain.
KW - Nested graph conditions
KW - Graph repair
KW - Model repair
KW - Consistency
KW - restoration
KW - Delta preservation
KW - Graph databases
KW - Model-driven
KW - engineering
Y1 - 2021
U6 - https://doi.org/10.1007/s10009-020-00584-x
SN - 1433-2779
SN - 1433-2787
VL - 23
IS - 3
SP - 369
EP - 410
PB - Springer
CY - Berlin ; Heidelberg
ER -
TY - JOUR
A1 - Schneider, Johannes
A1 - Wenig, Phillip
A1 - Papenbrock, Thorsten
T1 - Distributed detection of sequential anomalies in univariate time series
JF - The VLDB journal : the international journal on very large data bases
N2 - The automated detection of sequential anomalies in time series is an essential task for many applications, such as the monitoring of technical systems, fraud detection in high-frequency trading, or the early detection of disease symptoms. All these applications require the detection to find all sequential anomalies possibly fast on potentially very large time series. In other words, the detection needs to be effective, efficient and scalable w.r.t. the input size. Series2Graph is an effective solution based on graph embeddings that are robust against re-occurring anomalies and can discover sequential anomalies of arbitrary length and works without training data. Yet, Series2Graph is no t scalable due to its single-threaded approach; it cannot, in particular, process arbitrarily large sequences due to the memory constraints of a single machine. In this paper, we propose our distributed anomaly detection system, short DADS, which is an efficient and scalable adaptation of Series2Graph. Based on the actor programming model, DADS distributes the input time sequence, intermediate state and the computation to all processors of a cluster in a way that minimizes communication costs and synchronization barriers. Our evaluation shows that DADS is orders of magnitude faster than S2G, scales almost linearly with the number of processors in the cluster and can process much larger input sequences due to its scale-out property.
KW - Distributed programming
KW - Sequential anomaly
KW - Actor model
KW - Data mining
KW - Time series
Y1 - 2021
U6 - https://doi.org/10.1007/s00778-021-00657-6
SN - 1066-8888
SN - 0949-877X
VL - 30
IS - 4
SP - 579
EP - 602
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Schindler, Daniel
A1 - Moldenhawer, Ted
A1 - Stange, Maike
A1 - Lepro, Valentino
A1 - Beta, Carsten
A1 - Holschneider, Matthias
A1 - Huisinga, Wilhelm
T1 - Analysis of protrusion dynamics in amoeboid cell motility by means of regularized contour flows
JF - PLoS Computational Biology : a new community journal
N2 - Amoeboid cell motility is essential for a wide range of biological processes including wound healing, embryonic morphogenesis, and cancer metastasis. It relies on complex dynamical patterns of cell shape changes that pose long-standing challenges to mathematical modeling and raise a need for automated and reproducible approaches to extract quantitative morphological features from image sequences. Here, we introduce a theoretical framework and a computational method for obtaining smooth representations of the spatiotemporal contour dynamics from stacks of segmented microscopy images. Based on a Gaussian process regression we propose a one-parameter family of regularized contour flows that allows us to continuously track reference points (virtual markers) between successive cell contours. We use this approach to define a coordinate system on the moving cell boundary and to represent different local geometric quantities in this frame of reference. In particular, we introduce the local marker dispersion as a measure to identify localized membrane expansions and provide a fully automated way to extract the properties of such expansions, including their area and growth time. The methods are available as an open-source software package called AmoePy, a Python-based toolbox for analyzing amoeboid cell motility (based on time-lapse microscopy data), including a graphical user interface and detailed documentation. Due to the mathematical rigor of our framework, we envision it to be of use for the development of novel cell motility models. We mainly use experimental data of the social amoeba Dictyostelium discoideum to illustrate and validate our approach.
Author summary Amoeboid motion is a crawling-like cell migration that plays an important key role in multiple biological processes such as wound healing and cancer metastasis. This type of cell motility results from expanding and simultaneously contracting parts of the cell membrane. From fluorescence images, we obtain a sequence of points, representing the cell membrane, for each time step. By using regression analysis on these sequences, we derive smooth representations, so-called contours, of the membrane. Since the number of measurements is discrete and often limited, the question is raised of how to link consecutive contours with each other. In this work, we present a novel mathematical framework in which these links are described by regularized flows allowing a certain degree of concentration or stretching of neighboring reference points on the same contour. This stretching rate, the so-called local dispersion, is used to identify expansions and contractions of the cell membrane providing a fully automated way of extracting properties of these cell shape changes. We applied our methods to time-lapse microscopy data of the social amoeba Dictyostelium discoideum.
Y1 - 2021
U6 - https://doi.org/10.1371/journal.pcbi.1009268
SN - 1553-734X
SN - 1553-7358
VL - 17
IS - 8
PB - PLoS
CY - San Fransisco
ER -
TY - JOUR
A1 - Rüdian, Sylvio Leo
A1 - Vladova, Gergana
T1 - Kostenfreie Onlinekurse nachhaltig mit personalisiertem Marketing finanzieren
BT - ein Vorschlag zur synergetischen Kombination zweier datengetriebener Geschäftsmodelle
JF - HMD Praxis der Wirtschaftsinformatik
N2 - Selbstbestimmtes Lernen mit Onlinekursen findet zunehmend mehr Akzeptanz in unserer Gesellschaft. Lernende können mithilfe von Onlinekursen selbst festlegen, was sie wann lernen und Kurse können durch vielfältige Adaptionen an den Lernfortschritt der Nutzer angepasst und individualisiert werden. Auf der einen Seite ist eine große Zielgruppe für diese Lernangebote vorhanden. Auf der anderen Seite sind die Erstellung von Onlinekursen, ihre Bereitstellung, Wartung und Betreuung kostenintensiv, wodurch hochwertige Angebote häufig kostenpflichtig angeboten werden müssen, um als Anbieter zumindest kostenneutral agieren zu können. In diesem Beitrag erörtern und diskutieren wir ein offenes, nachhaltiges datengetriebenes zweiseitiges Geschäftsmodell zur Verwertung geprüfter Onlinekurse und deren kostenfreie Bereitstellung für jeden Lernenden. Kern des Geschäftsmodells ist die Nutzung der dabei entstehenden Verhaltensdaten, die daraus mögliche Ableitung von Persönlichkeitsmerkmalen und Interessen und deren Nutzung im kommerziellen Kontext. Dies ist eine bei der Websuche bereits weitläufig akzeptierte Methode, welche nun auf den Lernkontext übertragen wird. Welche Möglichkeiten, Herausforderungen, aber auch Barrieren überwunden werden müssen, damit das Geschäftsmodell nachhaltig und ethisch vertretbar funktioniert, werden zwei unabhängige, jedoch synergetisch verbundene Geschäftsmodelle vorgestellt und diskutiert. Zusätzlich wurde die Akzeptanz und Erwartung der Zielgruppe für das vorgestellte Geschäftsmodell untersucht, um notwendige Kernressourcen für die Praxis abzuleiten. Die Ergebnisse der Untersuchung zeigen, dass das Geschäftsmodell von den Nutzer*innen grundlegend akzeptiert wird. 10 % der Befragten würden es bevorzugen, mit virtuellen Assistenten – anstelle mit Tutor*innen zu lernen. Zudem ist der Großteil der Nutzer*innen sich nicht darüber bewusst, dass Persönlichkeitsmerkmale anhand des Nutzerverhaltens abgeleitet werden können.
KW - Onlinekurse
KW - Big Data
KW - Geschäftsmodell
KW - Werbung
KW - Marketing
KW - Canvas
Y1 - 2021
U6 - https://doi.org/10.1365/s40702-021-00720-4
SN - 1436-3011
VL - 58
IS - 3
SP - 507
EP - 520
PB - Springer Vieweg
CY - Wiesbaden
ER -
TY - THES
A1 - Rohloff, Tobias
T1 - Learning analytics at scale
BT - supporting learning and teaching in MOOCs with data-driven insights
N2 - Digital technologies are paving the way for innovative educational approaches. The learning format of Massive Open Online Courses (MOOCs) provides a highly accessible path to lifelong learning while being more affordable and flexible than face-to-face courses. Thereby, thousands of learners can enroll in courses mostly without admission restrictions, but this also raises challenges. Individual supervision by teachers is barely feasible, and learning persistence and success depend on students' self-regulatory skills. Here, technology provides the means for support. The use of data for decision-making is already transforming many fields, whereas in education, it is still a young research discipline. Learning Analytics (LA) is defined as the measurement, collection, analysis, and reporting of data about learners and their learning contexts with the purpose of understanding and improving learning and learning environments. The vast amount of data that MOOCs produce on the learning behavior and success of thousands of students provides the opportunity to study human learning and develop approaches addressing the demands of learners and teachers.
The overall purpose of this dissertation is to investigate the implementation of LA at the scale of MOOCs and to explore how data-driven technology can support learning and teaching in this context. To this end, several research prototypes have been iteratively developed for the HPI MOOC Platform. Hence, they were tested and evaluated in an authentic real-world learning environment. Most of the results can be applied on a conceptual level to other MOOC platforms as well. The research contribution of this thesis thus provides practical insights beyond what is theoretically possible. In total, four system components were developed and extended:
(1) The Learning Analytics Architecture: A technical infrastructure to collect, process, and analyze event-driven learning data based on schema-agnostic pipelining in a service-oriented MOOC platform. (2) The Learning Analytics Dashboard for Learners: A tool for data-driven support of self-regulated learning, in particular to enable learners to evaluate and plan their learning activities, progress, and success by themselves. (3) Personalized Learning Objectives: A set of features to better connect learners' success to their personal intentions based on selected learning objectives to offer guidance and align the provided data-driven insights about their learning progress. (4) The Learning Analytics Dashboard for Teachers: A tool supporting teachers with data-driven insights to enable the monitoring of their courses with thousands of learners, identify potential issues, and take informed action.
For all aspects examined in this dissertation, related research is presented, development processes and implementation concepts are explained, and evaluations are conducted in case studies. Among other findings, the usage of the learner dashboard in combination with personalized learning objectives demonstrated improved certification rates of 11.62% to 12.63%. Furthermore, it was observed that the teacher dashboard is a key tool and an integral part for teaching in MOOCs. In addition to the results and contributions, general limitations of the work are discussed—which altogether provide a solid foundation for practical implications and future research.
N2 - Digitale Technologien sind Wegbereiter für innovative Bildungsansätze. Das Lernformat der Massive Open Online Courses (MOOCs) bietet einen einfachen und globalen Zugang zu lebenslangem Lernen und ist oft kostengünstiger und flexibler als klassische Präsenzlehre. Dabei können sich Tausende von Lernenden meist ohne Zulassungsbeschränkung in Kurse einschreiben, wodurch jedoch auch Herausforderungen entstehen. Eine individuelle Betreuung durch Lehrende ist kaum möglich und das Durchhaltevermögen und der Lernerfolg hängen von selbstregulatorischen Fähigkeiten der Lernenden ab. Hier bietet Technologie die Möglichkeit zur Unterstützung. Die Nutzung von Daten zur Entscheidungsfindung transformiert bereits viele Bereiche, aber im Bildungswesen ist dies noch eine junge Forschungsdisziplin. Als Learning Analytics (LA) wird das Messen, Erfassen, Analysieren und Auswerten von Daten über Lernende und ihren Lernkontext verstanden, mit dem Ziel, das Lernen und die Lernumgebungen zu verstehen und zu verbessern. Die riesige Menge an Daten, die MOOCs über das Lernverhalten und den Lernerfolg produzieren, bietet die Möglichkeit, das menschliche Lernen zu studieren und Ansätze zu entwickeln, die den Anforderungen von Lernenden und Lehrenden gerecht werden.
Der Schwerpunkt dieser Dissertation liegt auf der Implementierung von LA für die Größenordnung von MOOCs und erforscht dabei, wie datengetriebene Technologie das Lernen und Lehren in diesem Kontext unterstützen kann. Zu diesem Zweck wurden mehrere Forschungsprototypen iterativ für die HPI-MOOC-Plattform entwickelt. Daher wurden diese in einer authentischen und realen Lernumgebung getestet und evaluiert. Die meisten Ergebnisse lassen sich auf konzeptioneller Ebene auch auf andere MOOC-Plattformen übertragen, wodurch der Forschungsbeitrag dieser Arbeit praktische Erkenntnisse über das theoretisch Mögliche hinaus liefert. Insgesamt wurden vier Systemkomponenten entwickelt und erweitert:
(1) Die LA-Architektur: Eine technische Infrastruktur zum Sammeln, Verarbeiten und Analysieren von ereignisgesteuerten Lerndaten basierend auf einem schemaagnostischem Pipelining in einer serviceorientierten MOOC-Plattform. (2) Das LA-Dashboard für Lernende: Ein Werkzeug zur datengesteuerten Unterstützung der Selbstregulierung, insbesondere um Lernende in die Lage zu versetzen, ihre Lernaktivitäten, ihren Fortschritt und ihren Lernerfolg selbst zu evaluieren und zu planen. (3) Personalisierte Lernziele: Eine Reihe von Funktionen, um den Lernerfolg besser mit persönlichen Absichten zu verknüpfen, die auf ausgewählten Lernzielen basieren, um Leitlinien anzubieten und die bereitgestellten datengetriebenen Einblicke über den Lernfortschritt darauf abzustimmen. (4) Das LA-Dashboard für Lehrende: Ein Hilfsmittel, das Lehrkräfte mit datengetriebenen Erkenntnissen unterstützt, um ihre Kurse mit Tausenden von Lernenden zu überblicken, mögliche Probleme zu erkennen und fundierte Maßnahmen zu ergreifen.
Für alle untersuchten Aspekte dieser Dissertation werden verwandte Forschungsarbeiten vorgestellt, Entwicklungsprozesse und Implementierungskonzepte erläutert und Evaluierungen in Fallstudien durchgeführt. Unter anderem konnte durch den Einsatz des Dashboards für Lernende in Kombination mit personalisierten Lernzielen verbesserte Zertifizierungsraten von 11,62% bis 12,63% nachgewiesen werden. Außerdem wurde beobachtet, dass das Dashboard für Lehrende ein entscheidendes Werkzeug und ein integraler Bestandteil für die Lehre in MOOCs ist. Neben den Ergebnissen und Beiträgen werden generelle Einschränkungen der Arbeit diskutiert, die insgesamt eine fundierte Grundlage für praktische Implikationen und zukünftige Forschungsvorhaben schaffen.
KW - Learning Analytics
KW - MOOCs
KW - Self-Regulated Learning
KW - E-Learning
KW - Service-Oriented Architecture
KW - Online Learning Environments
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-526235
ER -
TY - JOUR
A1 - Quinzan, Francesco
A1 - Göbel, Andreas
A1 - Wagner, Markus
A1 - Friedrich, Tobias
T1 - Evolutionary algorithms and submodular functions
BT - benefits of heavy-tailed mutations
JF - Natural computing : an innovative journal bridging biosciences and computer sciences ; an international journal
N2 - A core operator of evolutionary algorithms (EAs) is the mutation. Recently, much attention has been devoted to the study of mutation operators with dynamic and non-uniform mutation rates. Following up on this area of work, we propose a new mutation operator and analyze its performance on the (1 + 1) Evolutionary Algorithm (EA). Our analyses show that this mutation operator competes with pre-existing ones, when used by the (1 + 1) EA on classes of problems for which results on the other mutation operators are available. We show that the (1 + 1) EA using our mutation operator finds a (1/3)-approximation ratio on any non-negative submodular function in polynomial time. We also consider the problem of maximizing a symmetric submodular function under a single matroid constraint and show that the (1 + 1) EA using our operator finds a (1/3)-approximation within polynomial time. This performance matches that of combinatorial local search algorithms specifically designed to solve these problems and outperforms them with constant probability. Finally, we evaluate the performance of the (1 + 1) EA using our operator experimentally by considering two applications: (a) the maximum directed cut problem on real-world graphs of different origins, with up to 6.6 million vertices and 56 million edges and (b) the symmetric mutual information problem using a four month period air pollution data set. In comparison with uniform mutation and a recently proposed dynamic scheme, our operator comes out on top on these instances.
KW - Evolutionary algorithms
KW - Mutation operators
KW - Submodular functions
KW - Matroids
Y1 - 2021
U6 - https://doi.org/10.1007/s11047-021-09841-7
SN - 1572-9796
VL - 20
IS - 3
SP - 561
EP - 575
PB - Springer Science + Business Media B.V.
CY - Dordrecht
ER -
TY - JOUR
A1 - Pfitzner, Bjarne
A1 - Steckhan, Nico
A1 - Arnrich, Bert
T1 - Federated learning in a medical context
BT - a systematic literature review
JF - ACM transactions on internet technology : TOIT / Association for Computing
N2 - Data privacy is a very important issue. Especially in fields like medicine, it is paramount to abide by the existing privacy regulations to preserve patients' anonymity. However, data is required for research and training machine learning models that could help gain insight into complex correlations or personalised treatments that may otherwise stay undiscovered. Those models generally scale with the amount of data available, but the current situation often prohibits building large databases across sites. So it would be beneficial to be able to combine similar or related data from different sites all over the world while still preserving data privacy. Federated learning has been proposed as a solution for this, because it relies on the sharing of machine learning models, instead of the raw data itself. That means private data never leaves the site or device it was collected on. Federated learning is an emerging research area, and many domains have been identified for the application of those methods. This systematic literature review provides an extensive look at the concept of and research into federated learning and its applicability for confidential healthcare datasets.
KW - Federated learning
Y1 - 2021
U6 - https://doi.org/10.1145/3412357
SN - 1533-5399
SN - 1557-6051
VL - 21
IS - 2
SP - 1
EP - 31
PB - Association for Computing Machinery
CY - New York
ER -
TY - JOUR
A1 - Perugia, Giulia
A1 - Paetzel-Prüsmann, Maike
A1 - Alanenpää, Madelene
A1 - Castellano, Ginevra
T1 - I can see it in your eyes
BT - Gaze as an implicit cue of uncanniness and task performance in repeated interactions with robots
JF - Frontiers in robotics and AI
N2 - Over the past years, extensive research has been dedicated to developing robust platforms and data-driven dialog models to support long-term human-robot interactions. However, little is known about how people's perception of robots and engagement with them develop over time and how these can be accurately assessed through implicit and continuous measurement techniques. In this paper, we explore this by involving participants in three interaction sessions with multiple days of zero exposure in between. Each session consists of a joint task with a robot as well as two short social chats with it before and after the task. We measure participants' gaze patterns with a wearable eye-tracker and gauge their perception of the robot and engagement with it and the joint task using questionnaires. Results disclose that aversion of gaze in a social chat is an indicator of a robot's uncanniness and that the more people gaze at the robot in a joint task, the worse they perform. In contrast with most HRI literature, our results show that gaze toward an object of shared attention, rather than gaze toward a robotic partner, is the most meaningful predictor of engagement in a joint task. Furthermore, the analyses of gaze patterns in repeated interactions disclose that people's mutual gaze in a social chat develops congruently with their perceptions of the robot over time. These are key findings for the HRI community as they entail that gaze behavior can be used as an implicit measure of people's perception of robots in a social chat and of their engagement and task performance in a joint task.
KW - perception of robots
KW - long-term interaction
KW - mutual gaze
KW - engagement
KW - uncanny valley
Y1 - 2021
U6 - https://doi.org/10.3389/frobt.2021.645956
SN - 2296-9144
VL - 8
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Perscheid, Cindy
T1 - Integrative biomarker detection on high-dimensional gene expression data sets
BT - a survey on prior knowledge approaches
JF - Briefings in bioinformatics
N2 - Gene expression data provide the expression levels of tens of thousands of genes from several hundred samples. These data are analyzed to detect biomarkers that can be of prognostic or diagnostic use. Traditionally, biomarker detection for gene expression data is the task of gene selection. The vast number of genes is reduced to a few relevant ones that achieve the best performance for the respective use case. Traditional approaches select genes based on their statistical significance in the data set. This results in issues of robustness, redundancy and true biological relevance of the selected genes. Integrative analyses typically address these shortcomings by integrating multiple data artifacts from the same objects, e.g. gene expression and methylation data. When only gene expression data are available, integrative analyses instead use curated information on biological processes from public knowledge bases. With knowledge bases providing an ever-increasing amount of curated biological knowledge, such prior knowledge approaches become more powerful. This paper provides a thorough overview on the status quo of biomarker detection on gene expression data with prior biological knowledge. We discuss current shortcomings of traditional approaches, review recent external knowledge bases, provide a classification and qualitative comparison of existing prior knowledge approaches and discuss open challenges for this kind of gene selection.
KW - gene selection
KW - external knowledge bases
KW - biomarker detection
KW - gene
KW - expression
KW - prior knowledge
Y1 - 2021
U6 - https://doi.org/10.1093/bib/bbaa151
SN - 1467-5463
SN - 1477-4054
VL - 22
IS - 3
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - JOUR
A1 - Perscheid, Cindy
T1 - Comprior
BT - Facilitating the implementation and automated benchmarking of prior knowledge-based feature selection approaches on gene expression data sets
JF - BMC Bioinformatics
N2 - Background
Reproducible benchmarking is important for assessing the effectiveness of novel feature selection approaches applied on gene expression data, especially for prior knowledge approaches that incorporate biological information from online knowledge bases. However, no full-fledged benchmarking system exists that is extensible, provides built-in feature selection approaches, and a comprehensive result assessment encompassing classification performance, robustness, and biological relevance. Moreover, the particular needs of prior knowledge feature selection approaches, i.e. uniform access to knowledge bases, are not addressed. As a consequence, prior knowledge approaches are not evaluated amongst each other, leaving open questions regarding their effectiveness.
Results
We present the Comprior benchmark tool, which facilitates the rapid development and effortless benchmarking of feature selection approaches, with a special focus on prior knowledge approaches. Comprior is extensible by custom approaches, offers built-in standard feature selection approaches, enables uniform access to multiple knowledge bases, and provides a customizable evaluation infrastructure to compare multiple feature selection approaches regarding their classification performance, robustness, runtime, and biological relevance.
Conclusion
Comprior allows reproducible benchmarking especially of prior knowledge approaches, which facilitates their applicability and for the first time enables a comprehensive assessment of their effectiveness
KW - Feature selection
KW - Prior knowledge
KW - Gene expression
KW - Reproducible benchmarking
Y1 - 2021
U6 - https://doi.org/10.1186/s12859-021-04308-z
SN - 1471-2105
VL - 22
SP - 1
EP - 15
PB - Springer Nature
CY - London
ER -
TY - JOUR
A1 - Pawassar, Christian Matthias
A1 - Tiberius, Victor
T1 - Virtual reality in health care
BT - Bibliometric analysis
JF - JMIR Serious Games
N2 - Background:
Research into the application of virtual reality technology in the health care sector has rapidly increased, resulting in a large body of research that is difficult to keep up with.
Objective:
We will provide an overview of the annual publication numbers in this field and the most productive and influential countries, journals, and authors, as well as the most used, most co-occurring, and most recent keywords.
Methods:
Based on a data set of 356 publications and 20,363 citations derived from Web of Science, we conducted a bibliometric analysis using BibExcel, HistCite, and VOSviewer.
Results:
The strongest growth in publications occurred in 2020, accounting for 29.49% of all publications so far. The most productive countries are the United States, the United Kingdom, and Spain; the most influential countries are the United States, Canada, and the United Kingdom. The most productive journals are the Journal of Medical Internet Research (JMIR), JMIR Serious Games, and the Games for Health Journal; the most influential journals are Patient Education and Counselling, Medical Education, and Quality of Life Research. The most productive authors are Riva, del Piccolo, and Schwebel; the most influential authors are Finset, del Piccolo, and Eide. The most frequently occurring keywords other than “virtual” and “reality” are “training,” “trial,” and “patients.” The most relevant research themes are communication, education, and novel treatments; the most recent research trends are fitness and exergames.
Conclusions:
The analysis shows that the field has left its infant state and its specialization is advancing, with a clear focus on patient usability.
KW - virtual reality
KW - healthcare
KW - bibliometric analysis
KW - literature review
KW - citation analysis
KW - VR
KW - usability
KW - review
KW - health care
Y1 - 2021
U6 - https://doi.org/10.2196/32721
SN - 2291-9279
VL - 9
SP - 1
EP - 19
PB - JMIR Publications
CY - Toronto, Kanada
ET - 4
ER -
TY - THES
A1 - Pape, Tobias
T1 - Efficient compound values in virtual machines
N2 - Compound values are not universally supported in virtual machine (VM)-based programming systems and languages. However, providing data structures with value characteristics can be beneficial. On one hand, programming systems and languages can adequately represent physical quantities with compound values and avoid inconsistencies, for example, in representation of large numbers. On the other hand, just-in-time (JIT) compilers, which are often found in VMs, can rely on the fact that compound values are immutable, which is an important property in optimizing programs. Considering this, compound values have an optimization potential that can be put to use by implementing them in VMs in a way that is efficient in memory usage and execution time. Yet, optimized compound values in VMs face certain challenges: to maintain consistency, it should not be observable by the program whether compound values are represented in an optimized way by a VM; an optimization should take into account, that the usage of compound values can exhibit certain patterns at run-time; and that necessary value-incompatible properties due to implementation restrictions should be reduced.
We propose a technique to detect and compress common patterns of compound value usage at run-time to improve memory usage and execution speed. Our approach identifies patterns of frequent compound value references and introduces abbreviated forms for them. Thus, it is possible to store multiple inter-referenced compound values in an inlined memory representation, reducing the overhead of metadata and object references. We extend our approach by a notion of limited mutability, using cells that act as barriers for our approach and provide a location for shared, mutable access with the possibility of type specialization. We devise an extension to our approach that allows us to express automatic unboxing of boxed primitive data types in terms of our initial technique. We show that our approach is versatile enough to express another optimization technique that relies on values, such as Booleans, that are unique throughout a programming system. Furthermore, we demonstrate how to re-use learned usage patterns and optimizations across program runs, thus reducing the performance impact of pattern recognition.
We show in a best-case prototype that the implementation of our approach is feasible and can also be applied to general purpose programming systems, namely implementations of the Racket language and Squeak/Smalltalk. In several micro-benchmarks, we found that our approach can effectively reduce memory consumption and improve execution speed.
N2 - Zusammengesetzte Werte werden in VM-basierten Programmiersystemen und -sprachen nicht durchgängig unterstützt. Die Bereitstellung von Datenstrukturen mit Wertemerkmalen kann jedoch von Vorteil sein. Einerseits können Programmiersysteme und Sprachen physikalische Größen mit zusammengesetzten Werten, wie beispielsweise bei der Darstellung großer Zahlen, adäquat darstellen und Inkonsistenzen vermeiden. Andererseits können sich Just-in-time-Compiler, die oft in VMs zu finden sind, darauf verlassen, dass zusammengesetzte Werte unveränderlich sind, was eine wichtige Eigenschaft bei der Programmoptimierung ist. In Anbetracht dessen haben zusammengesetzte Werte ein Optimierungspotenzial, das genutzt werden kann, indem sie in VMs so implementiert werden, dass sie effizient in Speichernutzung und Ausführungszeit sind. Darüber hinaus stehen optimierte zusammengesetzte Werte in VMs vor bestimmten Herausforderungen: Um die Konsistenz zu erhalten, sollte das Programm nicht beobachten können, ob zusammengesetzte Werte durch eine VM in einer optimierten Weise dargestellt werden; eine Optimierung sollte berücksichtigen, dass die Verwendung von zusammengesetzten Werten bestimmte Muster zur Laufzeit aufweisen kann; und dass wertinkompatible Eigenschaften vermindert werden sollten, die nur aufgrund von Implementierungsbeschränkungen notwendig sind.
Wir schlagen eine Verfahrensweise vor, um gängige Muster der Verwendung von zusammengesetzten Werten zur Laufzeit zu erkennen und zu komprimieren, um die Speichernutzung und Ausführungsgeschwindigkeit zu verbessern. Unser Ansatz identifiziert Muster häufiger zusammengesetzter Wertreferenzen und führt für sie abgekürzte Formen ein. Dies ermöglicht es, mehrere miteinander verknüpfte zusammengesetzte Werte in einer eingebetteten Art und Weise im Speicher darzustellen, wodurch der Verwaltungsaufwand, der sich aus Metadaten und Objektreferenzen ergibt, reduziert wird. Wir erweitern unseren Ansatz um ein Konzept der eingeschränkten Veränderbarkeit, indem wir Zellen verwenden, die als Barrieren für unseren Ansatz dienen und einen Platz für einen gemeinsamen, schreibenden Zugriff mit der Möglichkeit der Typspezialisierung bieten. Wir
entwickeln eine Erweiterung unseres Ansatzes, die es uns ermöglicht, mithilfe unserer ursprünglichen Technik das automatische Entpacken von primitiven geboxten Datentypen auszudrücken. Wir zeigen, dass unser Ansatz vielseitig genug ist, um auch eine andere Optimierungstechnik auszudrücken, die sich auf einzigartige Werte in einem Programmiersystem, wie beispielsweise Booleans, stützt. Darüber hinaus zeigen wir, wie erlernte Nutzungsmuster und Optimierungen über Programmausführungen hinweg wiederverwendet werden können, wodurch die Auswirkungen der Mustererkennung auf die Leistung reduziert werden.
Wir zeigen in einem Best-Case-Prototyp, dass unser Ansatzes umsetzbar ist und auch auf allgemeinere Programmiersysteme wie Racket und Squeak/Smalltalk angewendet werden kann. In mehreren Mikro-Benchmarks haben wir festgestellt, dass unser Ansatz den Speicherverbrauch effektiv reduzieren und die Ausführungsgeschwindigkeit verbessern kann.
KW - Compound Values
KW - Objects
KW - Data Structure Optimization
KW - Virtual Machines
KW - Smalltalk
KW - Verbundwerte
KW - Objekte
KW - Datenstrukturoptimierung
KW - Virtuelle Maschinen
KW - Smalltalk
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-499134
ER -
TY - JOUR
A1 - Paetzel-Prüsmann, Maike
A1 - Perugia, Giulia
A1 - Castellano, Ginevra
T1 - The influence of robot personality on the development of uncanny feelings
JF - Computers in human behavior
N2 - Empirical investigations on the uncanny valley have almost solely focused on the analysis of people?s noninteractive perception of a robot at first sight. Recent studies suggest, however, that these uncanny first impressions may be significantly altered over an interaction. What is yet to discover is whether certain interaction patterns can lead to a faster decline in uncanny feelings. In this paper, we present a study in which participants with limited expertise in Computer Science played a collaborative geography game with a Furhat robot. During the game, Furhat displayed one of two personalities, which corresponded to two different interaction strategies. The robot was either optimistic and encouraging, or impatient and provocative. We performed the study in a science museum and recruited participants among the visitors. Our findings suggest that a robot that is rated high on agreeableness, emotional stability, and conscientiousness can indeed weaken uncanny feelings. This study has important implications for human-robot interaction design as it further highlights that a first impression, merely based on a robot?s appearance, is not indicative of the affinity people might develop towards it throughout an interaction. We thus argue that future work should emphasize investigations on exact interaction patterns that can help to overcome uncanny feelings.
KW - Human-robot interaction
KW - Uncanny valley
KW - Robot personality
KW - Human
KW - perception of robots
KW - Crowd-sourcing
KW - Multimodal behavior
Y1 - 2021
U6 - https://doi.org/10.1016/j.chb.2021.106756
SN - 0747-5632
SN - 1873-7692
VL - 120
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Oosthoek, Kris
A1 - Dörr, Christian
T1 - Cyber security threats to bitcoin exchanges
BT - adversary exploitation and laundering techniques
JF - IEEE transactions on network and service management : a publication of the IEEE
N2 - Bitcoin is gaining traction as an alternative store of value. Its market capitalization transcends all other cryptocurrencies in the market. But its high monetary value also makes it an attractive target to cyber criminal actors. Hacking campaigns usually target an ecosystem's weakest points. In Bitcoin, the exchange platforms are one of them. Each exchange breach is a threat not only to direct victims, but to the credibility of Bitcoin's entire ecosystem. Based on an extensive analysis of 36 breaches of Bitcoin exchanges, we show the attack patterns used to exploit Bitcoin exchange platforms using an industry standard for reporting intelligence on cyber security breaches. Based on this we are able to provide an overview of the most common attack vectors, showing that all except three hacks were possible due to relatively lax security. We show that while the security regimen of Bitcoin exchanges is subpar compared to other financial service providers, the use of stolen credentials, which does not require any hacking, is decreasing. We also show that the amount of BTC taken during a breach is decreasing, as well as the exchanges that terminate after being breached. Furthermore we show that overall security posture has improved, but still has major flaws. To discover adversarial methods post-breach, we have analyzed two cases of BTC laundering. Through this analysis we provide insight into how exchange platforms with lax cyber security even further increase the intermediary risk introduced by them into the Bitcoin ecosystem.
KW - Bitcoin
KW - Computer crime
KW - Cryptography
KW - Ecosystems
KW - Currencies
KW - Industries
KW - Vocabulary
KW - cryptocurrency exchanges
KW - cyber
KW - security
KW - cyber threat intelligence
KW - attacks
KW - vulnerabilities
KW - forensics
Y1 - 2021
U6 - https://doi.org/10.1109/TNSM.2020.3046145
SN - 1932-4537
VL - 18
IS - 2
SP - 1616
EP - 1628
PB - IEEE
CY - New York
ER -
TY - JOUR
A1 - Omranian, Sara
A1 - Angeleska, Angela
A1 - Nikoloski, Zoran
T1 - PC2P
BT - parameter-free network-based prediction of protein complexes
JF - Bioinformatics
N2 - Motivation:
Prediction of protein complexes from protein-protein interaction (PPI) networks is an important problem in systems biology, as they control different cellular functions. The existing solutions employ algorithms for network community detection that identify dense subgraphs in PPI networks. However, gold standards in yeast and human indicate that protein complexes can also induce sparse subgraphs, introducing further challenges in protein complex prediction.
Results:
To address this issue, we formalize protein complexes as biclique spanned subgraphs, which include both sparse and dense subgraphs. We then cast the problem of protein complex prediction as a network partitioning into biclique spanned subgraphs with removal of minimum number of edges, called coherent partition. Since finding a coherent partition is a computationally intractable problem, we devise a parameter-free greedy approximation algorithm, termed Protein Complexes from Coherent Partition (PC2P), based on key properties of biclique spanned subgraphs. Through comparison with nine contenders, we demonstrate that PC2P: (i) successfully identifies modular structure in networks, as a prerequisite for protein complex prediction, (ii) outperforms the existing solutions with respect to a composite score of five performance measures on 75% and 100% of the analyzed PPI networks and gold standards in yeast and human, respectively, and (iii,iv) does not compromise GO semantic similarity and enrichment score of the predicted protein complexes. Therefore, our study demonstrates that clustering of networks in terms of biclique spanned subgraphs is a promising framework for detection of complexes in PPI networks.
Y1 - 2021
U6 - https://doi.org/10.1093/bioinformatics/btaa1089
SN - 1367-4811
VL - 37
IS - 1
SP - 73
EP - 81
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - JOUR
A1 - Navarro, Marisa
A1 - Orejas, Fernando
A1 - Pino, Elvira
A1 - Lambers, Leen
T1 - A navigational logic for reasoning about graph properties
JF - Journal of logical and algebraic methods in programming
N2 - Graphs play an important role in many areas of Computer Science. In particular, our work is motivated by model-driven software development and by graph databases. For this reason, it is very important to have the means to express and to reason about the properties that a given graph may satisfy. With this aim, in this paper we present a visual logic that allows us to describe graph properties, including navigational properties, i.e., properties about the paths in a graph. The logic is equipped with a deductive tableau method that we have proved to be sound and complete.
KW - Graph logic
KW - Algebraic methods
KW - Formal modelling
KW - Specification
Y1 - 2021
U6 - https://doi.org/10.1016/j.jlamp.2020.100616
SN - 2352-2208
SN - 2352-2216
VL - 118
PB - Elsevier Science
CY - Amsterdam [u.a.]
ER -
TY - BOOK
A1 - Meinel, Christoph
A1 - Döllner, Jürgen Roland Friedrich
A1 - Weske, Mathias
A1 - Polze, Andreas
A1 - Hirschfeld, Robert
A1 - Naumann, Felix
A1 - Giese, Holger
A1 - Baudisch, Patrick
A1 - Friedrich, Tobias
A1 - Böttinger, Erwin
A1 - Lippert, Christoph
A1 - Dörr, Christian
A1 - Lehmann, Anja
A1 - Renard, Bernhard
A1 - Rabl, Tilmann
A1 - Uebernickel, Falk
A1 - Arnrich, Bert
A1 - Hölzle, Katharina
T1 - Proceedings of the HPI Research School on Service-oriented Systems Engineering 2020 Fall Retreat
N2 - Design and Implementation of service-oriented architectures imposes a huge number of research questions from the fields of software engineering, system analysis and modeling, adaptability, and application integration. Component orientation and web services are two approaches for design and realization of complex web-based system. Both approaches allow for dynamic application adaptation as well as integration of enterprise application.
Service-Oriented Systems Engineering represents a symbiosis of best practices in object-orientation, component-based development, distributed computing, and business process management. It provides integration of business and IT concerns.
The annual Ph.D. Retreat of the Research School provides each member the opportunity to present his/her current state of their research and to give an outline of a prospective Ph.D. thesis. Due to the interdisciplinary structure of the research school, this technical report covers a wide range of topics. These include but are not limited to: Human Computer Interaction and Computer Vision as Service; Service-oriented Geovisualization Systems; Algorithm Engineering for Service-oriented Systems; Modeling and Verification of Self-adaptive Service-oriented Systems; Tools and Methods for Software Engineering in Service-oriented Systems; Security Engineering of Service-based IT Systems; Service-oriented Information Systems; Evolutionary Transition of Enterprise Applications to Service Orientation; Operating System Abstractions for Service-oriented Computing; and Services Specification, Composition, and Enactment.
N2 - Der Entwurf und die Realisierung dienstbasierender Architekturen wirft eine Vielzahl von Forschungsfragestellungen aus den Gebieten der Softwaretechnik, der Systemmodellierung und -analyse, sowie der Adaptierbarkeit und Integration von Applikationen auf. Komponentenorientierung und WebServices sind zwei Ansätze für den effizienten Entwurf und die Realisierung komplexer Web-basierender Systeme. Sie ermöglichen die Reaktion auf wechselnde Anforderungen ebenso, wie die Integration großer komplexer Softwaresysteme.
"Service-Oriented Systems Engineering" repräsentiert die Symbiose bewährter Praktiken aus den Gebieten der Objektorientierung, der Komponentenprogrammierung, des verteilten Rechnen sowie der Geschäftsprozesse und berücksichtigt auch die Integration von Geschäftsanliegen und Informationstechnologien.
Die Klausurtagung des Forschungskollegs "Service-oriented Systems Engineering" findet einmal jährlich statt und bietet allen Kollegiaten die Möglichkeit den Stand ihrer aktuellen Forschung darzulegen. Bedingt durch die Querschnittstruktur des Kollegs deckt dieser Bericht ein weites Spektrum aktueller Forschungsthemen ab. Dazu zählen unter anderem Human Computer Interaction and Computer Vision as Service; Service-oriented Geovisualization Systems; Algorithm Engineering for Service-oriented Systems; Modeling and Verification of Self-adaptive Service-oriented Systems; Tools and Methods for Software Engineering in Service-oriented Systems; Security Engineering of Service-based IT Systems; Service-oriented Information Systems; Evolutionary Transition of Enterprise Applications to Service Orientation; Operating System Abstractions for Service-oriented Computing; sowie Services Specification, Composition, and Enactment.
T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 138
KW - Hasso Plattner Institute
KW - research school
KW - Ph.D. retreat
KW - service-oriented systems engineering
KW - Hasso-Plattner-Institut
KW - Forschungskolleg
KW - Klausurtagung
KW - Service-oriented Systems Engineering
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-504132
SN - 978-3-86956-513-2
SN - 1613-5652
SN - 2191-1665
IS - 138
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - BOOK
A1 - Maximova, Maria
A1 - Schneider, Sven
A1 - Giese, Holger
T1 - Interval probabilistic timed graph transformation systems
N2 - The formal modeling and analysis is of crucial importance for software development processes following the model based approach. We present the formalism of Interval Probabilistic Timed Graph Transformation Systems (IPTGTSs) as a high-level modeling language. This language supports structure dynamics (based on graph transformation), timed behavior (based on clocks, guards, resets, and invariants as in Timed Automata (TA)), and interval probabilistic behavior (based on Discrete Interval Probability Distributions). That is, for the probabilistic behavior, the modeler using IPTGTSs does not need to provide precise probabilities, which are often impossible to obtain, but rather provides a probability range instead from which a precise probability is chosen nondeterministically. In fact, this feature on capturing probabilistic behavior distinguishes IPTGTSs from Probabilistic Timed Graph Transformation Systems (PTGTSs) presented earlier.
Following earlier work on Interval Probabilistic Timed Automata (IPTA) and PTGTSs, we also provide an analysis tool chain for IPTGTSs based on inter-formalism transformations. In particular, we provide in our tool AutoGraph a translation of IPTGTSs to IPTA and rely on a mapping of IPTA to Probabilistic Timed Automata (PTA) to allow for the usage of the Prism model checker. The tool Prism can then be used to analyze the resulting PTA w.r.t. probabilistic real-time queries asking for worst-case and best-case probabilities to reach a certain set of target states in a given amount of time.
N2 - Die formale Modellierung und Analyse ist für Softwareentwicklungsprozesse nach dem modellbasierten Ansatz von entscheidender Bedeutung. Wir präsentieren den Formalismus von Interval Probabilistic Timed Graph Transformation Systems (IPTGTS) als Modellierungssprache auf hoher abstrakter Ebene. Diese Sprache unterstützt Strukturdynamik (basierend auf Graphtransformation), zeitgesteuertes Verhalten (basierend auf Clocks, Guards, Resets und Invarianten wie in Timed Automata (TA)) und intervallwahrscheinliches Verhalten (basierend auf diskreten Intervallwahrscheinlichkeitsverteilungen). Das heißt, für das probabilistische Verhalten muss der Modellierer, der IPTGTS verwendet, keine genauen Wahrscheinlichkeiten bereitstellen, die oft nicht zu bestimmen sind, sondern stattdessen einen Wahrscheinlichkeitsbereich bereitstellen, aus dem eine genaue Wahrscheinlichkeit nichtdeterministisch ausgewählt wird. Tatsächlich unterscheidet diese Funktion zur Erfassung des probabilistischen Verhaltens IPTGTS von den zuvor vorgestellten PTGTS (Probabilistic Timed Graph Transformation Systems).
Nach früheren Arbeiten zu Intervall Probabilistic Timed Automata (IPTA) und PTGTS bieten wir auch eine Analyse-Toolkette für IPTGTS, die auf Interformalismus-Transformationen basiert. Insbesondere bieten wir in unserem Tool AutoGraph eine Übersetzung von IPTGTSs in IPTA und stützen uns auf eine Zuordnung von IPTA zu probabilistischen zeitgesteuerten Automaten (PTA), um die Verwendung des Prism-Modellprüfers zu ermöglichen. Das Werkzeug Prism kann dann verwendet werden, um den resultierenden PTA bezüglich probabilistische Echtzeitabfragen (in denen nach Worst-Case- und Best-Case-Wahrscheinlichkeiten gefragt wird, um einen bestimmten Satz von Zielzuständen in einem bestimmten Zeitraum zu erreichen) zu analysieren.
T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 134
KW - cyber-physical systems
KW - graph transformation systems
KW - interval timed automata
KW - timed automata
KW - qualitative analysis
KW - quantitative analysis
KW - probabilistic timed systems
KW - interval probabilistic timed systems
KW - model checking
KW - cyber-physikalische Systeme
KW - Graphentransformationssysteme
KW - Interval Timed Automata
KW - Timed Automata
KW - qualitative Analyse
KW - quantitative Analyse
KW - probabilistische zeitgesteuerte Systeme
KW - interval probabilistische zeitgesteuerte Systeme
KW - Modellprüfung
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-512895
SN - 978-3-86956-502-6
SN - 1613-5652
SN - 2191-1665
IS - 134
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - THES
A1 - Makowski, Silvia
T1 - Discriminative Models for Biometric Identification using Micro- and Macro-Movements of the Eyes
N2 - Human visual perception is an active process. Eye movements either alternate between fixations and saccades or follow a smooth pursuit movement in case of moving targets. Besides these macroscopic gaze patterns, the eyes perform involuntary micro-movements during fixations which are commonly categorized into micro-saccades, drift and tremor. Eye movements are frequently studied in cognitive psychology, because they reflect a complex interplay of perception, attention and oculomotor control.
A common insight of psychological research is that macro-movements are highly individual. Inspired by this finding, there has been a considerable amount of prior research on oculomotoric biometric identification. However, the accuracy of known approaches is too low and the time needed for identification is too long for any practical application. This thesis explores discriminative models for the task of biometric identification.
Discriminative models optimize a quality measure of the predictions and are usually superior to generative approaches in discriminative tasks. However, using discriminative models requires to select a suitable form of data representation for sequential eye gaze data; i.e., by engineering features or constructing a sequence kernel and the performance of the classification model strongly depends on the data representation. We study two fundamentally different ways of representing eye gaze within a discriminative framework. In the first part of this thesis, we explore the integration of data and psychological background knowledge in the form of generative models to construct representations. To this end, we first develop generative statistical models of gaze behavior during reading and scene viewing that account for viewer-specific distributional properties of gaze patterns. In a second step, we develop a discriminative identification model by deriving Fisher kernel functions from these and several baseline models. We find that an SVM with Fisher kernel is able to reliably identify users based on their eye gaze during reading and scene viewing. However, since the generative models are constrained to use low-frequency macro-movements, they discard a significant amount of information contained in the raw eye tracking signal at a high cost: identification requires about one minute of input recording, which makes it inapplicable for real world biometric systems. In the second part of this thesis, we study a purely data-driven modeling approach. Here, we aim at automatically discovering the individual pattern hidden in the raw eye tracking signal. To this end, we develop a deep convolutional neural network DeepEyedentification that processes yaw and pitch gaze velocities and learns a representation end-to-end. Compared to prior work, this model increases the identification accuracy by one order of magnitude and the time to identification decreases to only seconds. The DeepEyedentificationLive model further improves upon the identification performance by processing binocular input and it also detects presentation-attacks.
We find that by learning a representation, the performance of oculomotoric identification and presentation-attack detection can be driven close to practical relevance for biometric applications. Eye tracking devices with high sampling frequency and precision are expensive and the applicability of eye movement as a biometric feature heavily depends on cost of recording devices.
In the last part of this thesis, we therefore study the requirements on data quality by evaluating the performance of the DeepEyedentificationLive network under reduced spatial and temporal resolution. We find that the method still attains a high identification accuracy at a temporal resolution of only 250 Hz and a precision of 0.03 degrees. Reducing both does not have an additive deteriorating effect.
KW - Machine Learning
Y1 - 2021
ER -
TY - JOUR
A1 - Magkos, Sotirios
A1 - Kupsch, Andreas
A1 - Bruno, Giovanni
T1 - Suppression of cone-beam artefacts with Direct Iterative Reconstruction Computed Tomography Trajectories (DIRECTT)
JF - Journal of imaging : open access journal
N2 - The reconstruction of cone-beam computed tomography data using filtered back-projection algorithms unavoidably results in severe artefacts. We describe how the Direct Iterative Reconstruction of Computed Tomography Trajectories (DIRECTT) algorithm can be combined with a model of the artefacts for the reconstruction of such data. The implementation of DIRECTT results in reconstructed volumes of superior quality compared to the conventional algorithms.
KW - iteration method
KW - signal processing
KW - X-ray imaging
KW - computed tomography
Y1 - 2021
U6 - https://doi.org/10.3390/jimaging7080147
SN - 2313-433X
VL - 7
IS - 8
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Loster, Michael
A1 - Koumarelas, Ioannis
A1 - Naumann, Felix
T1 - Knowledge transfer for entity resolution with siamese neural networks
JF - ACM journal of data and information quality
N2 - The integration of multiple data sources is a common problem in a large variety of applications. Traditionally, handcrafted similarity measures are used to discover, merge, and integrate multiple representations of the same entity-duplicates-into a large homogeneous collection of data. Often, these similarity measures do not cope well with the heterogeneity of the underlying dataset. In addition, domain experts are needed to manually design and configure such measures, which is both time-consuming and requires extensive domain expertise.
We propose a deep Siamese neural network, capable of learning a similarity measure that is tailored to the characteristics of a particular dataset. With the properties of deep learning methods, we are able to eliminate the manual feature engineering process and thus considerably reduce the effort required for model construction. In addition, we show that it is possible to transfer knowledge acquired during the deduplication of one dataset to another, and thus significantly reduce the amount of data required to train a similarity measure. We evaluated our method on multiple datasets and compare our approach to state-of-the-art deduplication methods. Our approach outperforms competitors by up to +26 percent F-measure, depending on task and dataset. In addition, we show that knowledge transfer is not only feasible, but in our experiments led to an improvement in F-measure of up to +4.7 percent.
KW - Entity resolution
KW - duplicate detection
KW - transfer learning
KW - neural
KW - networks
KW - metric learning
KW - similarity learning
KW - data quality
Y1 - 2021
U6 - https://doi.org/10.1145/3410157
SN - 1936-1955
SN - 1936-1963
VL - 13
IS - 1
PB - Association for Computing Machinery
CY - New York
ER -
TY - JOUR
A1 - Lambers, Leen
A1 - Orejas, Fernando
T1 - Transformation rules with nested application conditions
BT - critical pairs, initial conflicts & minimality
JF - Theoretical computer science
N2 - Recently, initial conflicts were introduced in the framework of M-adhesive categories as an important optimization of critical pairs. In particular, they represent a proper subset such that each conflict is represented in a minimal context by a unique initial one. The theory of critical pairs has been extended in the framework of M-adhesive categories to rules with nested application conditions (ACs), restricting the applicability of a rule and generalizing the well-known negative application conditions. A notion of initial conflicts for rules with ACs does not exist yet.
In this paper, on the one hand, we extend the theory of initial conflicts in the framework of M-adhesive categories to transformation rules with ACs. They represent a proper subset again of critical pairs for rules with ACs, and represent each conflict in a minimal context uniquely. They are moreover symbolic because we can show that in general no finite and complete set of conflicts for rules with ACs exists. On the other hand, we show that critical pairs are minimally M-complete, whereas initial conflicts are minimally complete. Finally, we introduce important special cases of rules with ACs for which we can obtain finite, minimally (M-)complete sets of conflicts.
KW - Graph transformation
KW - Critical pairs
KW - Initial conflicts
KW - Application
KW - conditions
Y1 - 2021
U6 - https://doi.org/10.1016/j.tcs.2021.07.023
SN - 0304-3975
SN - 1879-2294
VL - 884
SP - 44
EP - 67
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Ladleif, Jan
A1 - Weske, Mathias
T1 - Which event happened first?
BT - Deferred choice on blockchain using oracles
JF - Frontiers in blockchain
N2 - First come, first served: Critical choices between alternative actions are often made based on events external to an organization, and reacting promptly to their occurrence can be a major advantage over the competition. In Business Process Management (BPM), such deferred choices can be expressed in process models, and they are an important aspect of process engines. Blockchain-based process execution approaches are no exception to this, but are severely limited by the inherent properties of the platform: The isolated environment prevents direct access to external entities and data, and the non-continual runtime based entirely on atomic transactions impedes the monitoring and detection of events. In this paper we provide an in-depth examination of the semantics of deferred choice, and transfer them to environments such as the blockchain. We introduce and compare several oracle architectures able to satisfy certain requirements, and show that they can be implemented using state-of-the-art blockchain technology.
KW - business processes
KW - business process management
KW - deferred choice
KW - workflow patterns
KW - blockchain
KW - smart contracts
KW - oracles
KW - formal semantics
Y1 - 2021
U6 - https://doi.org/10.3389/fbloc.2021.758169
SN - 2624-7852
VL - 4
SP - 1
EP - 16
PB - Frontiers in Blockchain
CY - Lausanne, Schweiz
ER -
TY - GEN
A1 - Ladleif, Jan
A1 - Weske, Mathias
T1 - Which Event Happened First? Deferred Choice on Blockchain Using Oracles
T2 - Zweitveröffentlichungen der Universität Potsdam : Reihe der Digital Engineering Fakultät
N2 - First come, first served: Critical choices between alternative actions are often made based on events external to an organization, and reacting promptly to their occurrence can be a major advantage over the competition. In Business Process Management (BPM), such deferred choices can be expressed in process models, and they are an important aspect of process engines. Blockchain-based process execution approaches are no exception to this, but are severely limited by the inherent properties of the platform: The isolated environment prevents direct access to external entities and data, and the non-continual runtime based entirely on atomic transactions impedes the monitoring and detection of events. In this paper we provide an in-depth examination of the semantics of deferred choice, and transfer them to environments such as the blockchain. We introduce and compare several oracle architectures able to satisfy certain requirements, and show that they can be implemented using state-of-the-art blockchain technology.
T3 - Zweitveröffentlichungen der Universität Potsdam : Reihe der Digital Engineering Fakultät - 11
KW - business processes
KW - business process management
KW - deferred choice
KW - workflow patterns
KW - blockchain
KW - smart contracts
KW - oracles
KW - formal semantics
Y1 - 2022
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-550681
VL - 4
SP - 1
EP - 16
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Kühl, Tim
A1 - Münzer, Stefan
T1 - Learning about a serious disease
BT - when a personalized message is harmful unless you are happy
JF - Journal of computer assisted learning : JCAL
N2 - According to the personalization principle, addressing learners by means of a personalized compared to a nonpersonalized message can foster learning. Interestingly, though, a recent study found that the personalization principle can invert for aversive contents. The present study investigated whether the negative effect of a personalized message for an aversive content can be compensated when learners are in a happy mood. It was hypothesized that the negative effect of a personalized compared to a nonpersonalized message would only be observable for participants in a sad mood, while for participants in a happy mood a personalized message should be beneficial. A 2 x 2 between-subject design with mood (happy vs. sad) and personalization (personalized vs. nonpersonalized message) was used (N = 125 University students). Mood was experimentally varied prior to learning. Learning outcomes were measured by a retention and a transfer test. Results were essentially in line with the assumption: For participants in the sad mood condition, a negative effect of a personalized message was observable for retention and transfer. For participants in the happy mood condition, a positive effect of personalized message was observable for retention, but no effect for transfer. Note that the manipulation check measure for the mood induction procedure did not detect differences between conditions; this may be due to a shortcoming of the used measure (as indicated by an additional evaluation study). The study emphasizes the importance to consider the inherent emotional content of a topic, such as its aversive nature, since the emotional content of a topic can be a boundary condition for design principles in multimedia learning. The study also highlights the complex interplay of externally induced and inherently arising emotions.
KW - cognitive load
KW - emotional design
KW - mood
KW - multimedia learning
KW - personalization principle
Y1 - 2021
U6 - https://doi.org/10.1111/jcal.12571
SN - 0266-4909
SN - 1365-2729
VL - 37
IS - 5
SP - 1312
EP - 1323
PB - Wiley-Blackwell
CY - Oxford [u.a.]
ER -
TY - JOUR
A1 - Körppen, Tim
A1 - Ullrich, André
A1 - Bertheau, Clementine
T1 - Durchblick statt Bauchgefühl – Transformation zur Data-Driven Organization
JF - Wirtschaftsinformatik & Management
N2 - Um in der digitalisierten Wirtschaft mitzuspielen, müssen Unternehmen, Markt und insbesondere Kunden detailliert verstanden werden. Neben den „Big Playern“ aus dem Silicon Valley sieht der deutsche Mittelstand, der zu großen Teilen noch auf gewachsenen IT-Infrastrukturen und Prozessen agiert, oft alt aus. Um in den nächsten Jahren nicht gänzlich abgehängt zu werden, ist ein Umbruch notwendig. Sowohl Leistungserstellungsprozesse als auch Leistungsangebot müssen transparent und datenbasiert ausgerichtet werden. Nur so können Geschäftsvorfälle, das Marktgeschehen sowie Handeln der Akteure integrativ bewertet und fundierte Entscheidungen getroffen werden. In diesem Beitrag wird das Konzept der Data-Driven Organization vorgestellt und aufgezeigt, wie Unternehmen den eigenen Analyticsreifegrad ermitteln und in einem iterativen Transformationsprozess steigern können.
Y1 - 2021
U6 - https://doi.org/10.1365/s35764-021-00370-7
SN - 1867-5905
VL - 13
IS - 6
SP - 452
EP - 459
PB - Springer Gabler
CY - Wiesbaden
ER -
TY - JOUR
A1 - Kreowsky, Philipp
A1 - Stabernack, Christian Benno
T1 - A full-featured FPGA-based pipelined architecture for SIFT extraction
JF - IEEE access : practical research, open solutions / Institute of Electrical and Electronics Engineers
N2 - Image feature detection is a key task in computer vision. Scale Invariant Feature Transform (SIFT) is a prevalent and well known algorithm for robust feature detection. However, it is computationally demanding and software implementations are not applicable for real-time performance. In this paper, a versatile and pipelined hardware implementation is proposed, that is capable of computing keypoints and rotation invariant descriptors on-chip. All computations are performed in single precision floating-point format which makes it possible to implement the original algorithm with little alteration. Various rotation resolutions and filter kernel sizes are supported for images of any resolution up to ultra-high definition. For full high definition images, 84 fps can be processed. Ultra high definition images can be processed at 21 fps.
KW - Field programmable gate arrays
KW - Convolution
KW - Signal processing
KW - algorithms
KW - Kernel
KW - Image resolution
KW - Histograms
KW - Feature extraction
KW - Scale-invariant feature transform (SIFT)
KW - field-programmable gate array
KW - (FPGA)
KW - image processing
KW - computer vision
KW - parallel processing
KW - architecture
KW - real-time
KW - hardware architecture
Y1 - 2021
U6 - https://doi.org/10.1109/ACCESS.2021.3104387
SN - 2169-3536
VL - 9
SP - 128564
EP - 128573
PB - Inst. of Electr. and Electronics Engineers
CY - New York, NY
ER -
TY - CHAP
A1 - Krause, Hannes-Vincent
A1 - Baumann, Annika
T1 - The devil in disguise
BT - malicious envy’s impact on harmful interactions between social networking site users
T2 - ICIS 2021: user behaviors, engagement, and consequences
N2 - Envy constitutes a serious issue on Social Networking Sites (SNSs), as this painful emotion can severely diminish individuals' well-being. With prior research mainly focusing on the affective consequences of envy in the SNS context, its behavioral consequences remain puzzling. While negative interactions among SNS users are an alarming issue, it remains unclear to which extent the harmful emotion of malicious envy contributes to these toxic dynamics. This study constitutes a first step in understanding malicious envy’s causal impact on negative interactions within the SNS sphere. Within an online experiment, we experimentally induce malicious envy and measure its immediate impact on users’ negative behavior towards other users. Our findings show that malicious envy seems to be an essential factor fueling negativity among SNS users and further illustrate that this effect is especially pronounced when users are provided an objective factor to mask their envy and justify their norm-violating negative behavior.
Y1 - 2021
UR - https://aisel.aisnet.org/icis2021/user_behaivors/user_behaivors/21
PB - AIS Electronic Library (AISeL)
CY - [Erscheinungsort nicht ermittelbar]
ER -
TY - CHAP
A1 - Krasnova, Hanna
A1 - große Deters, Fenne
A1 - Gladkaya, Margarita
T1 - Examining social media as a driver of perfectionism
T2 - PACIS 2021 proceedings
N2 - Perfectionism is a personality disposition characterized by setting extremely high performance-standards coupled with critical self-evaluations. Often conceived as positive, perfectionism can yield not only beneficial but also deleterious outcomes ranging from anxiety to burnout. In this proposal, we set out to investigate the role of the technology and, particularly, social media in individuals’ strivings for perfection. We lay down theoretical bases for the possibility that social media plays a role in the development of perfectionism. To empirically test the hypothesized relationship, we propose a comprehensive study design based on the experience sampling method. Lastly, we provide an overview of the planned analysis and future steps.
Y1 - 2021
UR - https://aisel.aisnet.org/pacis2021/260
SN - 978-1-7336325-7-7
PB - AIS Electronic Library (AISeL)
CY - [Erscheinungsort nicht ermittelbar]
ER -
TY - JOUR
A1 - Koßmann, Jan
A1 - Papenbrock, Thorsten
A1 - Naumann, Felix
T1 - Data dependencies for query optimization
BT - a survey
JF - The VLDB journal : the international journal on very large data bases / publ. on behalf of the VLDB Endowment
N2 - Effective query optimization is a core feature of any database management system. While most query optimization techniques make use of simple metadata, such as cardinalities and other basic statistics, other optimization techniques are based on more advanced metadata including data dependencies, such as functional, uniqueness, order, or inclusion dependencies. This survey provides an overview, intuitive descriptions, and classifications of query optimization and execution strategies that are enabled by data dependencies. We consider the most popular types of data dependencies and focus on optimization strategies that target the optimization of relational database queries. The survey supports database vendors to identify optimization opportunities as well as DBMS researchers to find related work and open research questions.
KW - Query optimization
KW - Query execution
KW - Data dependencies
KW - Data profiling
KW - Unique column combinations
KW - Functional dependencies
KW - Order dependencies
KW - Inclusion dependencies
KW - Relational data
KW - SQL
Y1 - 2021
U6 - https://doi.org/10.1007/s00778-021-00676-3
SN - 1066-8888
SN - 0949-877X
VL - 31
IS - 1
SP - 1
EP - 22
PB - Springer
CY - Berlin ; Heidelberg ; New York
ER -
TY - JOUR
A1 - Kleemann, Steven
T1 - Cyber warfare and the "humanization" of international humanitarian law
JF - International journal of cyber warfare and terrorism
N2 - Cyber warfare is a timely and relevant issue and one of the most controversial in international humanitarian law (IHL). The aim of IHL is to set rules and limits in terms of means and methods of warfare. In this context, a key question arises: Has digital warfare rules or limits, and if so, how are these applicable? Traditional principles, developed over a long period, are facing a new dimension of challenges due to the rise of cyber warfare. This paper argues that to overcome this new issue, it is critical that new humanity-oriented approaches is developed with regard to cyber warfare. The challenge is to establish a legal regime for cyber-attacks, successfully addressing human rights norms and standards. While clarifying this from a legal perspective, the authors can redesign the sensitive equilibrium between humanity and military necessity, weighing the humanitarian aims of IHL and the protection of civilians-in combination with international human rights law and other relevant legal regimes-in a different manner than before.
KW - cyber-attack
KW - cyberwar
KW - IHL
KW - IHRL
KW - international human rights
KW - international humanitarian law
KW - law and technology
KW - new technologies
Y1 - 2021
SN - 978-1-7998-6177-5
U6 - https://doi.org/10.4018/IJCWT.2021040101
SN - 1947-3435
SN - 1947-3443
VL - 11
IS - 2
SP - 1
EP - 11
PB - IGI Global
CY - Hershey
ER -
TY - CHAP
A1 - Jacqmin, Julien
A1 - Özdemir, Paker Doğu
A1 - Fell Kurban, Caroline
A1 - Tunç Pekkan, Zelha
A1 - Koskinen, Johanna
A1 - Suonpää, Maija
A1 - Seng, Cheyvuth
A1 - Carlon, May Kristine Jonson
A1 - Gayed, John Maurice
A1 - Cross, Jeffrey S.
A1 - Langseth, Inger
A1 - Jacobsen, Dan Yngve
A1 - Haugsbakken, Halvdan
A1 - Bethge, Joseph
A1 - Serth, Sebastian
A1 - Staubitz, Thomas
A1 - Wuttke, Tobias
A1 - Nordemann, Oliver
A1 - Das, Partha-Pratim
A1 - Meinel, Christoph
A1 - Ponce, Eva
A1 - Srinath, Sindhu
A1 - Allegue, Laura
A1 - Perach, Shai
A1 - Alexandron, Giora
A1 - Corti, Paola
A1 - Baudo, Valeria
A1 - Turró, Carlos
A1 - Moura Santos, Ana
A1 - Nilsson, Charlotta
A1 - Maldonado-Mahauad, Jorge
A1 - Valdiviezo, Javier
A1 - Carvallo, Juan Pablo
A1 - Samaniego-Erazo, Nicolay
A1 - Poce, Antonella
A1 - Re, Maria Rosaria
A1 - Valente, Mara
A1 - Karp Gershon, Sa’ar
A1 - Ruipérez-Valiente, José A.
A1 - Despujol, Ignacio
A1 - Busquets, Jaime
A1 - Kerr, John
A1 - Lorenz, Anja
A1 - Schön, Sandra
A1 - Ebner, Martin
A1 - Wittke, Andreas
A1 - Beirne, Elaine
A1 - Nic Giolla Mhichíl, Mairéad
A1 - Brown, Mark
A1 - Mac Lochlainn, Conchúr
A1 - Topali, Paraskevi
A1 - Chounta, Irene-Angelica
A1 - Ortega-Arranz, Alejandro
A1 - Villagrá-Sobrino, Sara L.
A1 - Martínez-Monés, Alejandra
A1 - Blackwell, Virginia Katherine
A1 - Wiltrout, Mary Ellen
A1 - Rami Gaddem, Mohamed
A1 - Hernández Reyes, César Augusto
A1 - Nagahama, Toru
A1 - Buchem, Ilona
A1 - Okatan, Ebru
A1 - Khalil, Mohammad
A1 - Casiraghi, Daniela
A1 - Sancassani, Susanna
A1 - Brambilla, Federica
A1 - Mihaescu, Vlad
A1 - Andone, Diana
A1 - Vasiu, Radu
A1 - Şahin, Muhittin
A1 - Egloffstein, Marc
A1 - Bothe, Max
A1 - Rohloff, Tobias
A1 - Schenk, Nathanael
A1 - Schwerer, Florian
A1 - Ifenthaler, Dirk
A1 - Hense, Julia
A1 - Bernd, Mike
ED - Meinel, Christoph
ED - Staubitz, Thomas
ED - Schweiger, Stefanie
ED - Friedl, Christian
ED - Kiers, Janine
ED - Ebner, Martin
ED - Lorenz, Anja
ED - Ubachs, George
ED - Mongenet, Catherine
ED - Ruipérez-Valiente, José A.
ED - Cortes Mendez, Manoel
T1 - EMOOCs 2021
N2 - From June 22 to June 24, 2021, Hasso Plattner Institute, Potsdam, hosted the seventh European MOOC Stakeholder Summit (EMOOCs 2021) together with the eighth ACM Learning@Scale Conference.
Due to the COVID-19 situation, the conference was held fully online.
The boost in digital education worldwide as a result of the pandemic was also one of the main topics of this year’s EMOOCs. All institutions of learning have been forced to transform and redesign their educational methods, moving from traditional models to hybrid or completely online models at scale. The learnings, derived from practical experience and research, have been explored in EMOOCs 2021 in six tracks and additional workshops, covering various aspects of this field. In this publication, we present papers from the conference’s Experience Track, the Policy Track, the Business Track, the International Track, and the Workshops.
KW - e-learning
KW - microcredential
KW - MOOC
KW - digital education
KW - experience
KW - online course design
KW - online course creation
KW - higher education
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-510300
SN - 978-3-86956-512-5
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Huang, Yizhen
A1 - Richter, Eric
A1 - Kleickmann, Thilo
A1 - Wiepke, Axel
A1 - Richter, Dirk
T1 - Classroom complexity affects student teachers’ behavior in a VR classroom
JF - Computers & education : an international journal
N2 - Student teachers often struggle to keep track of everything that is happening in the classroom, and particularly to notice and respond when students cause disruptions. The complexity of the classroom environment is a potential contributing factor that has not been empirically tested. In this experimental study, we utilized a virtual reality (VR) classroom to examine whether classroom complexity affects the likelihood of student teachers noticing disruptions and how they react after noticing. Classroom complexity was operationalized as the number of disruptions and the existence of overlapping disruptions (multidimensionality) as well as the existence of parallel teaching tasks (simultaneity). Results showed that student teachers (n = 50) were less likely to notice the scripted disruptions, and also less likely to respond to the disruptions in a comprehensive and effortful manner when facing greater complexity. These results may have implications for both teacher training and the design of VR for training or research purpose. This study contributes to the field from two aspects: 1) it revealed how features of the classroom environment can affect student teachers' noticing of and reaction to disruptions; and 2) it extends the functionality of the VR environment-from a teacher training tool to a testbed of fundamental classroom processes that are difficult to manipulate in real-life.
KW - Augmented and virtual reality
KW - Simulations
KW - Improving classroom
KW - teaching
KW - Media in education
KW - Pedagogical issues
Y1 - 2021
U6 - https://doi.org/10.1016/j.compedu.2020.104100
SN - 0360-1315
SN - 1873-782X
VL - 163
PB - Elsevier
CY - Oxford
ER -
TY - THES
A1 - Hecher, Markus
T1 - Advanced tools and methods for treewidth-based problem solving
N2 - In the last decades, there was a notable progress in solving the well-known Boolean satisfiability (Sat) problem, which can be witnessed by powerful Sat solvers. One of the reasons why these solvers are so fast are structural properties of instances that are utilized by the solver’s interna. This thesis deals with the well-studied structural property treewidth, which measures the closeness of an instance to being a tree. In fact, there are many problems parameterized by treewidth that are solvable in polynomial time in the instance size when parameterized by treewidth.
In this work, we study advanced treewidth-based methods and tools for problems in knowledge representation and reasoning (KR). Thereby, we provide means to establish precise runtime results (upper bounds) for canonical problems relevant to KR. Then, we present a new type of problem reduction, which we call decomposition-guided (DG) that
allows us to precisely monitor the treewidth when reducing from one problem to another problem. This new reduction type will be the basis for a long-open lower bound result for quantified Boolean formulas and allows us to design a new methodology for establishing runtime lower bounds for problems parameterized by treewidth.
Finally, despite these lower bounds, we provide an efficient implementation of algorithms that adhere to treewidth. Our approach finds suitable abstractions of instances, which are subsequently refined in a recursive fashion, and it uses Sat solvers for solving subproblems. It turns out that our resulting solver is quite competitive for two canonical counting problems related to Sat.
N2 - In den letzten Jahrzehnten konnte ein beachtlicher Fortschritt im Bereich der Aussagenlogik verzeichnet werden. Dieser äußerte sich dadurch, dass für das wichtigste Problem in diesem Bereich, genannt „Sat“, welches sich mit der Fragestellung befasst, ob eine gegebene aussagenlogische Formel erfüllbar ist oder nicht, überwältigend schnelle Computerprogramme („Solver“) entwickelt werden konnten. Interessanterweise liefern diese Solver eine beeindruckende Leistung, weil sie oft selbst Probleminstanzen mit mehreren Millionen von Variablen spielend leicht lösen können. Auf der anderen Seite jedoch glaubt man in der Wissenschaft weitgehend an die Exponentialzeithypothese (ETH), welche besagt, dass man im schlimmsten Fall für das Lösen einer Instanz in diesem Bereich exponentielle Laufzeit in der Anzahl der Variablen benötigt. Dieser vermeintliche Widerspruch ist noch immer nicht vollständig geklärt, denn wahrscheinlich gibt es viele ineinandergreifende Gründe für die Schnelligkeit aktueller Sat Solver. Einer dieser Gründe befasst sich weitgehend mit strukturellen Eigenschaften von Probleminstanzen, die wohl indirekt und intern von diesen Solvern ausgenützt werden.
Diese Dissertation beschäftigt sich mit solchen strukturellen Eigenschaften, nämlich mit der sogenannten Baumweite. Die Baumweite ist sehr gut erforscht und versucht zu messen, wie groß der Abstand von Probleminstanzen zu Bäumen ist (Baumnähe). Allerdings ist dieser Parameter sehr generisch und bei Weitem nicht auf Problemstellungen der Aussagenlogik beschränkt. Tatsächlich gibt es viele weitere Probleme, die parametrisiert mit Baumweite in polynomieller Zeit gelöst werden können. Interessanterweise gibt es auch viele Probleme in der Wissensrepräsentation (KR), von denen man davon ausgeht, dass sie härter sind als das Problem Sat, die bei beschränkter Baumweite in polynomieller Zeit gelöst werden können. Ein prominentes Beispiel solcher Probleme ist das Problem QSat, welches sich für die Gültigkeit einer gegebenen quantifizierten, aussagenlogischen Formel (QBF), das sind aussagenlogische Formeln, wo gewisse Variablen existenziell bzw. universell quantifiziert werden können, befasst. Bemerkenswerterweise wird allerdings auch im Zusammenhang mit Baumweite, ähnlich zu Methoden der klassischen Komplexitätstheorie, die tatsächliche Komplexität (Härte) solcher Problemen quantifiziert, wo man die exakte Laufzeitabhängigkeit beim Problemlösen in der Baumweite (Stufe der Exponentialität) beschreibt.
Diese Arbeit befasst sich mit fortgeschrittenen, Baumweite-basierenden Methoden und Werkzeugen für Probleme der Wissensrepräsentation und künstlichen Intelligenz (AI). Dabei präsentieren wir Methoden, um präzise Laufzeitresultate (obere Schranken) für prominente Fragmente der Antwortmengenprogrammierung (ASP), welche ein kanonisches Paradigma zum Lösen von Problemen der Wissensrepräsentation darstellt, zu erhalten. Unsere Resultate basieren auf dem Konzept der dynamischen Programmierung, die angeleitet durch eine sogenannte Baumzerlegung und ähnlich dem Prinzip „Teile-und-herrsche“ funktioniert. Solch eine Baumzerlegung ist eine konkrete, strukturelle Zerlegung einer Probleminstanz, die sich stark an der Baumweite orientiert.
Des Weiteren präsentieren wir einen neuen Typ von Problemreduktion, den wir als „decomposition-guided (DG)“, also „zerlegungsangeleitet“, bezeichnen. Dieser Reduktionstyp erlaubt es, Baumweiteerhöhungen und -verringerungen während einer Problemreduktion von einem bestimmten Problem zu einem anderen Problem präzise zu untersuchen und zu kontrollieren. Zusätzlich ist dieser neue Reduktionstyp die Basis, um ein lange offen gebliebenes Resultat betreffend quantifizierter, aussagenlogischer Formeln zu zeigen. Tatsächlich sind wir damit in der Lage, präzise untere Schranken, unter der Annahme der Exponentialzeithypothese, für das Problem QSat bei beschränkter Baumweite zu zeigen. Genauer gesagt können wir mit diesem Konzept der DG Reduktionen zeigen, dass das Problem QSat, beschränkt auf Quantifizierungsrang ` und parametrisiert mit Baumweite k, im Allgemeinen nicht besser als in einer Laufzeit, die `-fach exponentiell in der Baumweite und polynomiell in der Instanzgröße ist1, lösen. Dieses Resultat hebt auf nicht-inkrementelle Weise ein bekanntes Ergebnis für Quantifizierungsrang 2 auf beliebige Quantifizierungsränge, allerdings impliziert es auch sehr viele weitere Konsequenzen.
Das Resultat über die untere Schranke des Problems QSat erlaubt es, eine neue Methodologie zum Zeigen unterer Schranken einer Vielzahl von Problemen der Wissensrepräsentation und künstlichen Intelligenz, zu etablieren. In weiterer Konsequenz können wir damit auch zeigen, dass die oberen Schranken sowie die DG Reduktionen dieser Arbeit unter der Hypothese ETH „eng“ sind, d.h., sie können wahrscheinlich nicht mehr signifikant verbessert werden. Die Ergebnisse betreffend der unteren Schranken für QSat und die dazugehörige Methodologie konstituieren in gewisser Weise eine Hierarchie von über Baumweite parametrisierte Laufzeitklassen. Diese Laufzeitklassen können verwendet werden, um die Härte von Problemen für das Ausnützen von Baumweite zu quantifizieren und diese entsprechend ihrer Laufzeitabhängigkeit bezüglich Baumweite zu kategorisieren.
Schlussendlich und trotz der genannten Resultate betreffend unterer Schranken sind wir im Stande, eine effiziente Implementierung von Algorithmen basierend auf dynamischer Programmierung, die entlang einer Baumzerlegung angeleitet wird, zur Verfügung zu stellen. Dabei funktioniert unser Ansatz dahingehend, indem er probiert, passende Abstraktionen von Instanzen zu finden, die dann im Endeffekt sukzessive und auf rekursive Art und Weise verfeinert und verbessert werden. Inspiriert durch die enorme Effizienz und Effektivität der Sat Solver, ist unsere Implementierung ein hybrider Ansatz, weil sie den starken Gebrauch von Sat Solvern zum Lösen diverser Subprobleme, die während der dynamischen Programmierung auftreten, pflegt. Dabei stellt sich heraus, dass der resultierende Solver unserer Implementierung im Bezug auf Effizienz beim Lösen von zwei kanonischen, Sat-verwandten Zählproblemen mit bestehenden Solvern locker mithalten kann. Tatsächlich sind wir im Stande, Instanzen, wo die oberen Schranken von Baumweite 260 übersteigen, zu lösen. Diese überraschende Beobachtung zeigt daher, dass Baumweite ein wichtiger Parameter sein könnte, der wohl in modernen Designs von Solvern berücksichtigt werden sollte.
KW - Treewidth
KW - Dynamic Programming
KW - Knowledge Representation and Reasoning
KW - Artificial Intelligence
KW - Computational Complexity
KW - Parameterized Complexity
KW - Answer Set Programming
KW - Exponential Time Hypothesis
KW - Lower Bounds
KW - Algorithms
KW - Algorithmen
KW - Antwortmengenprogrammierung
KW - Künstliche Intelligenz
KW - Komplexitätstheorie
KW - Dynamische Programmierung
KW - Exponentialzeit Hypothese
KW - Wissensrepräsentation und Schlussfolgerung
KW - Untere Schranken
KW - Parametrisierte Komplexität
KW - Baumweite
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-512519
ER -
TY - JOUR
A1 - Haarmann, Stephan
A1 - Holfter, Adrian
A1 - Pufahl, Luise
A1 - Weske, Mathias
T1 - Formal framework for checking compliance of data-driven case management
JF - Journal on data semantics : JoDS
N2 - Business processes are often specified in descriptive or normative models. Both types of models should adhere to internal and external regulations, such as company guidelines or laws. Employing compliance checking techniques, it is possible to verify process models against rules. While traditionally compliance checking focuses on well-structured processes, we address case management scenarios. In case management, knowledge workers drive multi-variant and adaptive processes. Our contribution is based on the fragment-based case management approach, which splits a process into a set of fragments. The fragments are synchronized through shared data but can, otherwise, be dynamically instantiated and executed. We formalize case models using Petri nets. We demonstrate the formalization for design-time and run-time compliance checking and present a proof-of-concept implementation. The application of the implemented compliance checking approach to a use case exemplifies its effectiveness while designing a case model. The empirical evaluation on a set of case models for measuring the performance of the approach shows that rules can often be checked in less than a second.
KW - Compliance checking
KW - Case management
KW - Model verification
KW - Data-centric
KW - processes
Y1 - 2021
U6 - https://doi.org/10.1007/s13740-021-00120-3
SN - 1861-2032
SN - 1861-2040
VL - 10
IS - 1-2
SP - 143
EP - 163
PB - Springer
CY - Heidelberg
ER -
TY - JOUR
A1 - Göbel, Andreas
A1 - Lagodzinski, Gregor J. A.
A1 - Seidel, Karen
T1 - Counting homomorphisms to trees modulo a prime
JF - ACM transactions on computation theory : TOCT / Association for Computing Machinery
N2 - Many important graph-theoretic notions can be encoded as counting graph homomorphism problems, such as partition functions in statistical physics, in particular independent sets and colourings. In this article, we study the complexity of #(p) HOMSTOH, the problem of counting graph homomorphisms from an input graph to a graph H modulo a prime number p. Dyer and Greenhill proved a dichotomy stating that the tractability of non-modular counting graph homomorphisms depends on the structure of the target graph. Many intractable cases in non-modular counting become tractable in modular counting due to the common phenomenon of cancellation. In subsequent studies on counting modulo 2, however, the influence of the structure of H on the tractability was shown to persist, which yields similar dichotomies.
Our main result states that for every tree H and every prime p the problem #pHOMSTOH is either polynomial time computable or #P-p-complete. This relates to the conjecture of Faben and Jerrum stating that this dichotomy holds for every graph H when counting modulo 2. In contrast to previous results on modular counting, the tractable cases of #pHOMSTOH are essentially the same for all values of the modulo when H is a tree. To prove this result, we study the structural properties of a homomorphism. As an important interim result, our study yields a dichotomy for the problem of counting weighted independent sets in a bipartite graph modulo some prime p. These results are the first suggesting that such dichotomies hold not only for the modulo 2 case but also for the modular counting functions of all primes p.
KW - Graph homomorphisms
KW - modular counting
KW - complexity dichotomy
Y1 - 2021
U6 - https://doi.org/10.1145/3460958
SN - 1942-3454
SN - 1942-3462
VL - 13
IS - 3
SP - 1
EP - 33
PB - Association for Computing Machinery
CY - New York
ER -
TY - JOUR
A1 - Grüner, Andreas
A1 - Mühle, Alexander
A1 - Meinel, Christoph
T1 - ATIB
BT - Design and evaluation of an architecture for brokered self-sovereign identity integration and trust-enhancing attribute aggregation for service provider
JF - IEEE access : practical research, open solutions / Institute of Electrical and Electronics Engineers
N2 - Identity management is a principle component of securing online services. In the advancement of traditional identity management patterns, the identity provider remained a Trusted Third Party (TTP). The service provider and the user need to trust a particular identity provider for correct attributes amongst other demands. This paradigm changed with the invention of blockchain-based Self-Sovereign Identity (SSI) solutions that primarily focus on the users. SSI reduces the functional scope of the identity provider to an attribute provider while enabling attribute aggregation. Besides that, the development of new protocols, disregarding established protocols and a significantly fragmented landscape of SSI solutions pose considerable challenges for an adoption by service providers. We propose an Attribute Trust-enhancing Identity Broker (ATIB) to leverage the potential of SSI for trust-enhancing attribute aggregation. Furthermore, ATIB abstracts from a dedicated SSI solution and offers standard protocols. Therefore, it facilitates the adoption by service providers. Despite the brokered integration approach, we show that ATIB provides a high security posture. Additionally, ATIB does not compromise the ten foundational SSI principles for the users.
KW - Blockchains
KW - Protocols
KW - Authentication
KW - Licenses
KW - Security
KW - Privacy
KW - Identity management systems
KW - Attribute aggregation
KW - attribute assurance
KW - digital identity
KW - identity broker
KW - self-sovereign identity
KW - trust model
Y1 - 2021
U6 - https://doi.org/10.1109/ACCESS.2021.3116095
SN - 2169-3536
VL - 9
SP - 138553
EP - 138570
PB - Institute of Electrical and Electronics Engineers
CY - New York, NY
ER -
TY - JOUR
A1 - Gautam, Khem Raj
A1 - Zhang, Guoqiang
A1 - Landwehr, Niels
A1 - Adolphs, Julian
T1 - Machine learning for improvement of thermal conditions inside a hybrid ventilated animal building
JF - Computers and electronics in agriculture : COMPAG online ; an international journal
N2 - In buildings with hybrid ventilation, natural ventilation opening positions (windows), mechanical ventilation rates, heating, and cooling are manipulated to maintain desired thermal conditions. The indoor temperature is regulated solely by ventilation (natural and mechanical) when the external conditions are favorable to save external heating and cooling energy. The ventilation parameters are determined by a rule-based control scheme, which is not optimal. This study proposes a methodology to enable real-time optimum control of ventilation parameters. We developed offline prediction models to estimate future thermal conditions from the data collected from building in operation. The developed offline model is then used to find the optimal controllable ventilation parameters in real-time to minimize the setpoint deviation in the building. With the proposed methodology, the experimental building's setpoint deviation improved for 87% of time, on average, by 0.53 degrees C compared to the current deviations.
KW - Animal building
KW - Natural ventilation
KW - Automatically controlled windows
KW - Machine learning
KW - Optimization
Y1 - 2021
U6 - https://doi.org/10.1016/j.compag.2021.106259
SN - 0168-1699
SN - 1872-7107
VL - 187
PB - Elsevier Science
CY - Amsterdam [u.a.]
ER -
TY - JOUR
A1 - Freitas da Cruz, Harry
A1 - Pfahringer, Boris
A1 - Martensen, Tom
A1 - Schneider, Frederic
A1 - Meyer, Alexander
A1 - Böttinger, Erwin
A1 - Schapranow, Matthieu-Patrick
T1 - Using interpretability approaches to update "black-box" clinical prediction models
BT - an external validation study in nephrology
JF - Artificial intelligence in medicine : AIM
N2 - Despite advances in machine learning-based clinical prediction models, only few of such models are actually deployed in clinical contexts. Among other reasons, this is due to a lack of validation studies. In this paper, we present and discuss the validation results of a machine learning model for the prediction of acute kidney injury in cardiac surgery patients initially developed on the MIMIC-III dataset when applied to an external cohort of an American research hospital. To help account for the performance differences observed, we utilized interpretability methods based on feature importance, which allowed experts to scrutinize model behavior both at the global and local level, making it possible to gain further insights into why it did not behave as expected on the validation cohort. The knowledge gleaned upon derivation can be potentially useful to assist model update during validation for more generalizable and simpler models. We argue that interpretability methods should be considered by practitioners as a further tool to help explain performance differences and inform model update in validation studies.
KW - Clinical predictive modeling
KW - Nephrology
KW - Validation
KW - Interpretability
KW - methods
Y1 - 2021
U6 - https://doi.org/10.1016/j.artmed.2020.101982
SN - 0933-3657
SN - 1873-2860
VL - 111
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Fandinno, Jorge
A1 - Laferriere, Francois
A1 - Romero, Javier
A1 - Schaub, Torsten H.
A1 - Son, Tran Cao
T1 - Planning with incomplete information in quantified answer set programming
JF - Theory and practice of logic programming
N2 - We present a general approach to planning with incomplete information in Answer Set Programming (ASP). More precisely, we consider the problems of conformant and conditional planning with sensing actions and assumptions. We represent planning problems using a simple formalism where logic programs describe the transition function between states, the initial states and the goal states. For solving planning problems, we use Quantified Answer Set Programming (QASP), an extension of ASP with existential and universal quantifiers over atoms that is analogous to Quantified Boolean Formulas (QBFs). We define the language of quantified logic programs and use it to represent the solutions different variants of conformant and conditional planning. On the practical side, we present a translation-based QASP solver that converts quantified logic programs into QBFs and then executes a QBF solver, and we evaluate experimentally the approach on conformant and conditional planning benchmarks.
KW - answer set programming
KW - planning
KW - quantified logics
Y1 - 2021
U6 - https://doi.org/10.1017/S1471068421000259
SN - 1471-0684
SN - 1475-3081
VL - 21
IS - 5
SP - 663
EP - 679
PB - Cambridge University Press
CY - Cambridge
ER -
TY - JOUR
A1 - Doerr, Benjamin
A1 - Krejca, Martin Stefan
T1 - A simplified run time analysis of the univariate marginal distribution algorithm on LeadingOnes
JF - Theoretical computer science
N2 - With elementary means, we prove a stronger run time guarantee for the univariate marginal distribution algorithm (UMDA) optimizing the LEADINGONES benchmark function in the desirable regime with low genetic drift. If the population size is at least quasilinear, then, with high probability, the UMDA samples the optimum in a number of iterations that is linear in the problem size divided by the logarithm of the UMDA's selection rate. This improves over the previous guarantee, obtained by Dang and Lehre (2015) via the deep level-based population method, both in terms of the run time and by demonstrating further run time gains from small selection rates. Under similar assumptions, we prove a lower bound that matches our upper bound up to constant factors.
KW - Theory
KW - Estimation-of-distribution algorithm
KW - Run time analysis
Y1 - 2021
U6 - https://doi.org/10.1016/j.tcs.2020.11.028
SN - 0304-3975
SN - 1879-2294
VL - 851
SP - 121
EP - 128
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - De Freitas, Jessica K.
A1 - Johnson, Kipp W.
A1 - Golden, Eddye
A1 - Nadkarni, Girish N.
A1 - Dudley, Joel T.
A1 - Böttinger, Erwin
A1 - Glicksberg, Benjamin S.
A1 - Miotto, Riccardo
T1 - Phe2vec
BT - Automated disease phenotyping based on unsupervised embeddings from electronic health records
JF - Patterns
N2 - Robust phenotyping of patients from electronic health records (EHRs) at scale is a challenge in clinical informatics. Here, we introduce Phe2vec, an automated framework for disease phenotyping from EHRs based on unsupervised learning and assess its effectiveness against standard rule-based algorithms from Phenotype KnowledgeBase (PheKB). Phe2vec is based on pre-computing embeddings of medical concepts and patients' clinical history. Disease phenotypes are then derived from a seed concept and its neighbors in the embedding space. Patients are linked to a disease if their embedded representation is close to the disease phenotype. Comparing Phe2vec and PheKB cohorts head-to-head using chart review, Phe2vec performed on par or better in nine out of ten diseases. Differently from other approaches, it can scale to any condition and was validated against widely adopted expert-based standards. Phe2vec aims to optimize clinical informatics research by augmenting current frameworks to characterize patients by condition and derive reliable disease cohorts.
Y1 - 2021
U6 - https://doi.org/10.1016/j.patter.2021.100337
SN - 2666-3899
VL - 2
IS - 9
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Cseh, Ágnes
A1 - Kavitha, Telikepalli
T1 - Popular matchings in complete graphs
JF - Algorithmica : an international journal in computer science
N2 - Our input is a complete graph G on n vertices where each vertex has a strict ranking of all other vertices in G. The goal is to construct a matching in G that is popular. A matching M is popular if M does not lose a head-to-head election against any matching M ': here each vertex casts a vote for the matching in {M,M '} in which it gets a better assignment. Popular matchings need not exist in the given instance G and the popular matching problem is to decide whether one exists or not. The popular matching problem in G is easy to solve for odd n. Surprisingly, the problem becomes NP-complete for even n, as we show here. This is one of the few graph theoretic problems efficiently solvable when n has one parity and NP-complete when n has the other parity.
KW - Popular matching
KW - Complexity
KW - Stable matching
Y1 - 2021
U6 - https://doi.org/10.1007/s00453-020-00791-7
SN - 0178-4617
SN - 1432-0541
VL - 83
IS - 5
SP - 1493
EP - 1523
PB - Springer
CY - New York
ER -
TY - JOUR
A1 - Cseh, Ágnes
A1 - Juhos, Attila
T1 - Pairwise preferences in the stable marriage problem
JF - ACM Transactions on Economics and Computation / Association for Computing Machinery
N2 - We study the classical, two-sided stable marriage problem under pairwise preferences. In the most general setting, agents are allowed to express their preferences as comparisons of any two of their edges, and they also have the right to declare a draw or even withdraw from such a comparison. This freedom is then gradually restricted as we specify six stages of orderedness in the preferences, ending with the classical case of strictly ordered lists. We study all cases occurring when combining the three known notions of stability-weak, strong, and super-stability-under the assumption that each side of the bipartite market obtains one of the six degrees of orderedness. By designing three polynomial algorithms and two NP-completeness proofs, we determine the complexity of all cases not yet known and thus give an exact boundary in terms of preference structure between tractable and intractable cases.
KW - Stable marriage
KW - intransitivity
KW - acyclic preferences
KW - poset
KW - weakly
KW - stable matching
KW - strongly stable matching
KW - super stable matching
Y1 - 2021
U6 - https://doi.org/10.1145/3434427
SN - 2167-8375
SN - 2167-8383
VL - 9
IS - 1
PB - Association for Computing Machinery
CY - New York
ER -
TY - JOUR
A1 - Combi, Carlo
A1 - Oliboni, Barbara
A1 - Weske, Mathias
A1 - Zerbato, Francesca
T1 - Seamless conceptual modeling of processes with transactional and analytical data
JF - Data & knowledge engineering
N2 - In the field of Business Process Management (BPM), modeling business processes and related data is a critical issue since process activities need to manage data stored in databases. The connection between processes and data is usually handled at the implementation level, even if modeling both processes and data at the conceptual level should help designers in improving business process models and identifying requirements for implementation. Especially in data -and decision-intensive contexts, business process activities need to access data stored both in databases and data warehouses. In this paper, we complete our approach for defining a novel conceptual view that bridges process activities and data. The proposed approach allows the designer to model the connection between business processes and database models and define the operations to perform, providing interesting insights on the overall connected perspective and hints for identifying activities that are crucial for decision support.
KW - Conceptual modeling
KW - Business process modeling
KW - BPMN
KW - Data modeling
KW - Data warehouse
KW - Decision support
Y1 - 2021
U6 - https://doi.org/10.1016/j.datak.2021.101895
SN - 0169-023X
SN - 1872-6933
VL - 134
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Brede, Nuria
A1 - Botta, Nicola
T1 - On the correctness of monadic backward induction
JF - Journal of functional programming
N2 - In control theory, to solve a finite-horizon sequential decision problem (SDP) commonly means to find a list of decision rules that result in an optimal expected total reward (or cost) when taking a given number of decision steps. SDPs are routinely solved using Bellman's backward induction. Textbook authors (e.g. Bertsekas or Puterman) typically give more or less formal proofs to show that the backward induction algorithm is correct as solution method for deterministic and stochastic SDPs. Botta, Jansson and Ionescu propose a generic framework for finite horizon, monadic SDPs together with a monadic version of backward induction for solving such SDPs. In monadic SDPs, the monad captures a generic notion of uncertainty, while a generic measure function aggregates rewards. In the present paper, we define a notion of correctness for monadic SDPs and identify three conditions that allow us to prove a correctness result for monadic backward induction that is comparable to textbook correctness proofs for ordinary backward induction. The conditions that we impose are fairly general and can be cast in category-theoretical terms using the notion of Eilenberg-Moore algebra. They hold in familiar settings like those of deterministic or stochastic SDPs, but we also give examples in which they fail. Our results show that backward induction can safely be employed for a broader class of SDPs than usually treated in textbooks. However, they also rule out certain instances that were considered admissible in the context of Botta et al. 's generic framework. Our development is formalised in Idris as an extension of the Botta et al. framework and the sources are available as supplementary material.
Y1 - 2021
U6 - https://doi.org/10.1017/S0956796821000228
SN - 1469-7653
SN - 0956-7968
VL - 31
PB - Cambridge University Press
CY - Cambridge
ER -
TY - JOUR
A1 - Bordihn, Henning
A1 - Vaszil, György
T1 - Reversible parallel communicating finite automata systems
JF - Acta informatica
N2 - We study the concept of reversibility in connection with parallel communicating systems of finite automata (PCFA in short). We define the notion of reversibility in the case of PCFA (also covering the non-deterministic case) and discuss the relationship of the reversibility of the systems and the reversibility of its components. We show that a system can be reversible with non-reversible components, and the other way around, the reversibility of the components does not necessarily imply the reversibility of the system as a whole. We also investigate the computational power of deterministic centralized reversible PCFA. We show that these very simple types of PCFA (returning or non-returning) can recognize regular languages which cannot be accepted by reversible (deterministic) finite automata, and that they can even accept languages that are not context-free. We also separate the deterministic and non-deterministic variants in the case of systems with non-returning communication. We show that there are languages accepted by non-deterministic centralized PCFA, which cannot be recognized by any deterministic variant of the same type.
KW - Finite automata
KW - Reversibility
KW - Systems of parallel communicating
KW - automata
Y1 - 2021
U6 - https://doi.org/10.1007/s00236-021-00396-9
SN - 0001-5903
SN - 1432-0525
VL - 58
IS - 4
SP - 263
EP - 279
PB - Springer
CY - Berlin ; Heidelberg ; New York, NY
ER -
TY - JOUR
A1 - Bordihn, Henning
A1 - Holzer, Markus
T1 - On the number of active states in finite automata
JF - Acta informatica
N2 - We introduce a new measure of descriptional complexity on finite automata, called the number of active states. Roughly speaking, the number of active states of an automaton A on input w counts the number of different states visited during the most economic computation of the automaton A for the word w. This concept generalizes to finite automata and regular languages in a straightforward way. We show that the number of active states of both finite automata and regular languages is computable, even with respect to nondeterministic finite automata. We further compare the number of active states to related measures for regular languages. In particular, we show incomparability to the radius of regular languages and that the difference between the number of active states and the total number of states needed in finite automata for a regular language can be of exponential order.
Y1 - 2021
U6 - https://doi.org/10.1007/s00236-021-00397-8
SN - 0001-5903
SN - 1432-0525
VL - 58
IS - 4
SP - 301
EP - 318
PB - Springer
CY - Berlin ; Heidelberg [u.a.]
ER -
TY - JOUR
A1 - Borchert, Florian
A1 - Mock, Andreas
A1 - Tomczak, Aurelie
A1 - Hügel, Jonas
A1 - Alkarkoukly, Samer
A1 - Knurr, Alexander
A1 - Volckmar, Anna-Lena
A1 - Stenzinger, Albrecht
A1 - Schirmacher, Peter
A1 - Debus, Jürgen
A1 - Jäger, Dirk
A1 - Longerich, Thomas
A1 - Fröhling, Stefan
A1 - Eils, Roland
A1 - Bougatf, Nina
A1 - Sax, Ulrich
A1 - Schapranow, Matthieu-Patrick
T1 - Correction to: Knowledge bases and software support for variant interpretation in precision oncology
JF - Briefings in bioinformatics
Y1 - 2021
U6 - https://doi.org/10.1093/bib/bbab246
SN - 1467-5463
SN - 1477-4054
VL - 22
IS - 6
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - JOUR
A1 - Borchert, Florian
A1 - Mock, Andreas
A1 - Tomczak, Aurelie
A1 - Hügel, Jonas
A1 - Alkarkoukly, Samer
A1 - Knurr, Alexander
A1 - Volckmar, Anna-Lena
A1 - Stenzinger, Albrecht
A1 - Schirmacher, Peter
A1 - Debus, Jürgen
A1 - Jäger, Dirk
A1 - Longerich, Thomas
A1 - Fröhling, Stefan
A1 - Eils, Roland
A1 - Bougatf, Nina
A1 - Sax, Ulrich
A1 - Schapranow, Matthieu-Patrick
T1 - Knowledge bases and software support for variant interpretation in precision oncology
JF - Briefings in bioinformatics
N2 - Precision oncology is a rapidly evolving interdisciplinary medical specialty. Comprehensive cancer panels are becoming increasingly available at pathology departments worldwide, creating the urgent need for scalable cancer variant annotation and molecularly informed treatment recommendations. A wealth of mainly academia-driven knowledge bases calls for software tools supporting the multi-step diagnostic process. We derive a comprehensive list of knowledge bases relevant for variant interpretation by a review of existing literature followed by a survey among medical experts from university hospitals in Germany. In addition, we review cancer variant interpretation tools, which integrate multiple knowledge bases. We categorize the knowledge bases along the diagnostic process in precision oncology and analyze programmatic access options as well as the integration of knowledge bases into software tools. The most commonly used knowledge bases provide good programmatic access options and have been integrated into a range of software tools. For the wider set of knowledge bases, access options vary across different parts of the diagnostic process. Programmatic access is limited for information regarding clinical classifications of variants and for therapy recommendations. The main issue for databases used for biological classification of pathogenic variants and pathway context information is the lack of standardized interfaces. There is no single cancer variant interpretation tool that integrates all identified knowledge bases. Specialized tools are available and need to be further developed for different steps in the diagnostic process.
KW - HiGHmed
KW - personalized medicine
KW - molecular tumor board
KW - data integration
KW - cancer therapy
Y1 - 2021
U6 - https://doi.org/10.1093/bib/bbab134
SN - 1467-5463
SN - 1477-4054
VL - 22
IS - 6
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - JOUR
A1 - Bonnet, Philippe
A1 - Dong, Xin Luna
A1 - Naumann, Felix
A1 - Tözün, Pınar
T1 - VLDB 2021
BT - Designing a hybrid conference
JF - SIGMOD record
N2 - The 47th International Conference on Very Large Databases (VLDB'21) was held on August 16-20, 2021 as a hybrid conference. It attracted 180 in-person attendees in Copenhagen and 840 remote attendees. In this paper, we describe our key decisions as general chairs and program committee chairs and share the lessons we learned.
Y1 - 2021
U6 - https://doi.org/10.1145/3516431.3516447
SN - 0163-5808
SN - 1943-5835
VL - 50
IS - 4
SP - 50
EP - 53
PB - Association for Computing Machinery
CY - New York
ER -
TY - JOUR
A1 - Boissier, Martin
T1 - Robust and budget-constrained encoding configurations for in-memory database systems
JF - Proceedings of the VLDB Endowment
N2 - Data encoding has been applied to database systems for decades as it mitigates bandwidth bottlenecks and reduces storage requirements. But even in the presence of these advantages, most in-memory database systems use data encoding only conservatively as the negative impact on runtime performance can be severe. Real-world systems with large parts being infrequently accessed and cost efficiency constraints in cloud environments require solutions that automatically and efficiently select encoding techniques, including heavy-weight compression. In this paper, we introduce workload-driven approaches to automaticaly determine memory budget-constrained encoding configurations using greedy heuristics and linear programming. We show for TPC-H, TPC-DS, and the Join Order Benchmark that optimized encoding configurations can reduce the main memory footprint significantly without a loss in runtime performance over state-of-the-art dictionary encoding. To yield robust selections, we extend the linear programming-based approach to incorporate query runtime constraints and mitigate unexpected performance regressions.
KW - General Earth and Planetary Sciences
KW - Water Science and Technology
KW - Geography, Planning and Development
Y1 - 2021
U6 - https://doi.org/10.14778/3503585.3503588
SN - 2150-8097
VL - 15
IS - 4
SP - 780
EP - 793
PB - Association for Computing Machinery (ACM)
CY - [New York]
ER -
TY - GEN
A1 - Benson, Lawrence
A1 - Makait, Hendrik
A1 - Rabl, Tilmann
T1 - Viper
BT - An Efficient Hybrid PMem-DRAM Key-Value Store
T2 - Zweitveröffentlichungen der Universität Potsdam : Reihe der Digital Engineering Fakultät
N2 - Key-value stores (KVSs) have found wide application in modern software systems. For persistence, their data resides in slow secondary storage, which requires KVSs to employ various techniques to increase their read and write performance from and to the underlying medium. Emerging persistent memory (PMem) technologies offer data persistence at close-to-DRAM speed, making them a promising alternative to classical disk-based storage. However, simply drop-in replacing existing storage with PMem does not yield good results, as block-based access behaves differently in PMem than on disk and ignores PMem's byte addressability, layout, and unique performance characteristics. In this paper, we propose three PMem-specific access patterns and implement them in a hybrid PMem-DRAM KVS called Viper. We employ a DRAM-based hash index and a PMem-aware storage layout to utilize the random-write speed of DRAM and efficient sequential-write performance PMem. Our evaluation shows that Viper significantly outperforms existing KVSs for core KVS operations while providing full data persistence. Moreover, Viper outperforms existing PMem-only, hybrid, and disk-based KVSs by 4-18x for write workloads, while matching or surpassing their get performance.
T3 - Zweitveröffentlichungen der Universität Potsdam : Reihe der Digital Engineering Fakultät - 20
KW - memory
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-559664
SN - 2150-8097
IS - 9
ER -
TY - JOUR
A1 - Benson, Lawrence
A1 - Makait, Hendrik
A1 - Rabl, Tilmann
T1 - Viper
BT - An Efficient Hybrid PMem-DRAM Key-Value Store
JF - Proceedings of the VLDB Endowment
N2 - Key-value stores (KVSs) have found wide application in modern software systems. For persistence, their data resides in slow secondary storage, which requires KVSs to employ various techniques to increase their read and write performance from and to the underlying medium. Emerging persistent memory (PMem) technologies offer data persistence at close-to-DRAM speed, making them a promising alternative to classical disk-based storage. However, simply drop-in replacing existing storage with PMem does not yield good results, as block-based access behaves differently in PMem than on disk and ignores PMem's byte addressability, layout, and unique performance characteristics. In this paper, we propose three PMem-specific access patterns and implement them in a hybrid PMem-DRAM KVS called Viper. We employ a DRAM-based hash index and a PMem-aware storage layout to utilize the random-write speed of DRAM and efficient sequential-write performance PMem. Our evaluation shows that Viper significantly outperforms existing KVSs for core KVS operations while providing full data persistence. Moreover, Viper outperforms existing PMem-only, hybrid, and disk-based KVSs by 4-18x for write workloads, while matching or surpassing their get performance.
KW - memory
Y1 - 2021
U6 - https://doi.org/10.14778/3461535.3461543
SN - 2150-8097
VL - 14
IS - 9
SP - 1544
EP - 1556
PB - Association for Computing Machinery
CY - New York
ER -
TY - BOOK
A1 - Bartz, Christian
A1 - Krestel, Ralf
T1 - Deep learning for computer vision in the art domain
BT - proceedings of the master seminar on practical introduction to deep learning for computer vision, HPI WS 20/21
N2 - In recent years, computer vision algorithms based on machine learning have seen rapid development. In the past, research mostly focused on solving computer vision problems such as image classification or object detection on images displaying natural scenes. Nowadays other fields such as the field of cultural heritage, where an abundance of data is available, also get into the focus of research. In the line of current research endeavours, we collaborated with the Getty Research Institute which provided us with a challenging dataset, containing images of paintings and drawings. In this technical report, we present the results of the seminar "Deep Learning for Computer Vision". In this seminar, students of the Hasso Plattner Institute evaluated state-of-the-art approaches for image classification, object detection and image recognition on the dataset of the Getty Research Institute. The main challenge when applying modern computer vision methods to the available data is the availability of annotated training data, as the dataset provided by the Getty Research Institute does not contain a sufficient amount of annotated samples for the training of deep neural networks. However, throughout the report we show that it is possible to achieve satisfying to very good results, when using further publicly available datasets, such as the WikiArt dataset, for the training of machine learning models.
N2 - Methoden zur Anwendung von maschinellem Lernen für das maschinelle Sehen haben sich in den letzten Jahren stark weiterentwickelt. Dabei konzentrierte sich die Forschung hauptsächlich auf die Lösung von Problemen im Bereich der Bildklassifizierung, oder der Objekterkennung aus Bildern mit natürlichen Motiven. Mehr und mehr kommen zusätzlich auch andere Inhaltsbereiche, vor allem aus dem kulturellen Umfeld in den Fokus der Forschung. Kulturforschungsinstitute, wie das Getty Research Institute, besitzen eine Vielzahl von digitalisierten Dokumenten, die bisher noch nicht analysiert wurden. Im Rahmen einer Zusammenarbeit, überließ das Getty Research Institute uns einen Datensatz, bestehend aus Photos von Kunstwerken. In diesem technischen Bericht präsentieren wir die Ergebnisse des Masterseminars "Deep Learning for Computer Vision", in dem Studierende des Hasso-Plattner-Instituts den Stand der Kunst, bei der Anwendung von Bildklassifizierungs, Objekterkennungs und Image Retrieval Algorithmen evaluierten. Eine besondere Schwierigkeit war, dass es nicht möglich ist bestehende Verfahren direkt auf dem Datensatz anzuwenden, da keine, bzw. kaum Annotationen für das Training von Machine Learning Modellen verfügbar sind. In den einzelnen Teilen des Berichts zeigen wir jedoch, dass es möglich ist unter Zuhilfenahme von weiteren öffentlich verfügbaren Datensätzen, wie dem WikiArt Datensatz, zufriedenstellende bis sehr gute Ergebnisse für die einzelnen Analyseaufgaben zu erreichen.
T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 139
KW - computer vision
KW - cultural heritage
KW - art analysis
KW - maschinelles Sehen
KW - kulturelles Erbe
KW - Kunstanalyse
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-512906
SN - 978-3-86956-514-9
SN - 1613-5652
SN - 2191-1665
IS - 139
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - BOOK
A1 - Baltzer, Wanda
A1 - Hradilak, Theresa
A1 - Pfennigschmidt, Lara
A1 - Prestin, Luc Maurice
A1 - Spranger, Moritz
A1 - Stadlinger, Simon
A1 - Wendt, Leo
A1 - Lincke, Jens
A1 - Rein, Patrick
A1 - Church, Luke
A1 - Hirschfeld, Robert
T1 - An individual-centered approach to visualize people’s opinions and demographic information
N2 - The noble way to substantiate decisions that affect many people is to ask these people for their opinions. For governments that run whole countries, this means asking all citizens for their views to consider their situations and needs.
Organizations such as Africa's Voices Foundation, who want to facilitate communication between decision-makers and citizens of a country, have difficulty mediating between these groups. To enable understanding, statements need to be summarized and visualized. Accomplishing these goals in a way that does justice to the citizens' voices and situations proves challenging. Standard charts do not help this cause as they fail to create empathy for the people behind their graphical abstractions. Furthermore, these charts do not create trust in the data they are representing as there is no way to see or navigate back to the underlying code and the original data. To fulfill these functions, visualizations would highly benefit from interactions to explore the displayed data, which standard charts often only limitedly provide.
To help improve the understanding of people's voices, we developed and categorized 80 ideas for new visualizations, new interactions, and better connections between different charts, which we present in this report. From those ideas, we implemented 10 prototypes and two systems that integrate different visualizations. We show that this integration allows consistent appearance and behavior of visualizations. The visualizations all share the same main concept: representing each individual with a single dot. To realize this idea, we discuss technologies that efficiently allow the rendering of a large number of these dots. With these visualizations, direct interactions with representations of individuals are achievable by clicking on them or by dragging a selection around them. This direct interaction is only possible with a bidirectional connection from the visualization to the data it displays. We discuss different strategies for bidirectional mappings and the trade-offs involved. Having unified behavior across visualizations enhances exploration. For our prototypes, that includes grouping, filtering, highlighting, and coloring of dots. Our prototyping work was enabled by the development environment Lively4. We explain which parts of Lively4 facilitated our prototyping process. Finally, we evaluate our approach to domain problems and our developed visualization concepts.
Our work provides inspiration and a starting point for visualization development in this domain. Our visualizations can improve communication between citizens and their government and motivate empathetic decisions. Our approach, combining low-level entities to create visualizations, provides value to an explorative and empathetic workflow. We show that the design space for visualizing this kind of data has a lot of potential and that it is possible to combine qualitative and quantitative approaches to data analysis.
N2 - Der noble Weg, Entscheidungen, die viele Menschen betreffen, zu begründen, besteht darin, diese Menschen nach ihrer Meinung zu fragen. Für Regierungen, die ganze Länder führen, bedeutet dies, alle Bürger nach ihrer Meinung zu fragen, um ihre Situationen und Bedürfnisse zu berücksichtigen.
Organisationen wie die Africa's Voices Foundation, die die Kommunikation zwischen Entscheidungsträgern und Bürgern eines Landes erleichtern wollen, haben Schwierigkeiten, zwischen diesen Gruppen zu vermitteln. Um Verständnis zu ermöglichen, müssen die Aussagen zusammengefasst und visualisiert werden. Diese Ziele auf eine Weise zu erreichen, die den Stimmen und Situationen der Bürgerinnen und Bürger gerecht wird, erweist sich als Herausforderung. Standardgrafiken helfen dabei nicht weiter, da es ihnen nicht gelingt, Empathie für die Menschen hinter ihren grafischen Abstraktionen zu schaffen. Darüber hinaus schaffen diese Diagramme kein Vertrauen in die Daten, die sie darstellen, da es keine Möglichkeit gibt, den verwendeten Code und die Originaldaten zu sehen oder zu ihnen zurück zu navigieren. Um diese Funktionen zu erfüllen, würden Visualisierungen sehr von Interaktionen zur Erkundung der angezeigten Daten profitieren, die Standardgrafiken oft nur begrenzt bieten.
Um das Verständnis der Stimmen der Menschen zu verbessern, haben wir 80 Ideen für neue Visualisierungen, neue Interaktionen und bessere Verbindungen zwischen verschiedenen Diagrammen entwickelt und kategorisiert, die wir in diesem Bericht vorstellen. Aus diesen Ideen haben wir 10 Prototypen und zwei Systeme implementiert, die verschiedene Visualisierungen integrieren. Wir zeigen, dass diese Integration ein einheitliches Erscheinungsbild und Verhalten der Visualisierungen ermöglicht. Die Visualisierungen haben alle das gleiche Grundkonzept: Jedes Individuum wird durch einen einzigen Punkt dargestellt. Um diese Idee zu verwirklichen, diskutieren wir Technologien, die die effiziente Darstellung einer großen Anzahl dieser Punkte ermöglichen. Mit diesen Visualisierungen sind direkte Interaktionen mit Darstellungen von Individuen möglich, indem man auf sie klickt oder eine Auswahl um sie herumzieht. Diese direkte Interaktion ist nur mit einer bidirektionalen Verbindung von der Visualisierung zu den angezeigten Daten möglich. Wir diskutieren verschiedene Strategien für bidirektionale Mappings und die damit verbundenen Kompromisse. Ein einheitliches Verhalten über Visualisierungen hinweg verbessert die Exploration. Für unsere Prototypen umfasst dies Gruppierung, Filterung, Hervorhebung und Einfärbung von Punkten. Unsere Arbeit an den Prototypen wurde durch die Entwicklungsumgebung Lively4 ermöglicht. Wir erklären, welche Teile von Lively4 unseren Prototyping-Prozess erleichtert haben. Schließlich bewerten wir unsere Herangehensweise an Domänenprobleme und die von uns entwickelten Visualisierungskonzepte.
Unsere Arbeit liefert Inspiration und einen Ausgangspunkt für die Entwicklung von Visualisierungen in diesem Bereich. Unsere Visualisierungen können die Kommunikation zwischen Bürgern und ihrer Regierung verbessern und einfühlsame Entscheidungen motivieren. Unser Ansatz, bei dem wir niedrigstufige Entitäten zur Erstellung von Visualisierungen kombinieren, bietet einen wertvollen Ansatz für einen explorativen und einfühlsamen Arbeitsablauf. Wir zeigen, dass der Designraum für die Visualisierung dieser Art von Daten ein großes Potenzial hat und dass es möglich ist, qualitative und quantitative Ansätze zur Datenanalyse zu kombinieren.
T3 - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 136
KW - data visualization
KW - demographic information
KW - visualization concept exploration
KW - web-based development environment
KW - Datenvisualisierung
KW - demografische Informationen
KW - Visualisierungskonzept-Exploration
KW - web-basierte Entwicklungsumgebung
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-491457
SN - 978-3-86956-504-0
SN - 1613-5652
SN - 2191-1665
IS - 136
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - JOUR
A1 - Ayzel, Georgy
A1 - Heistermann, Maik
T1 - The effect of calibration data length on the performance of a conceptual hydrological model versus LSTM and GRU
BT - a case study for six basins from the CAMELS dataset
JF - Computers & geosciences : an international journal devoted to the publication of papers on all aspects of geocomputation and to the distribution of computer programs and test data sets ; an official journal of the International Association for Mathematical Geology
N2 - We systematically explore the effect of calibration data length on the performance of a conceptual hydrological model, GR4H, in comparison to two Artificial Neural Network (ANN) architectures: Long Short-Term Memory Networks (LSTM) and Gated Recurrent Units (GRU), which have just recently been introduced to the field of hydrology. We implemented a case study for six river basins across the contiguous United States, with 25 years of meteorological and discharge data. Nine years were reserved for independent validation; two years were used as a warm-up period, one year for each of the calibration and validation periods, respectively; from the remaining 14 years, we sampled increasing amounts of data for model calibration, and found pronounced differences in model performance. While GR4H required less data to converge, LSTM and GRU caught up at a remarkable rate, considering their number of parameters. Also, LSTM and GRU exhibited the higher calibration instability in comparison to GR4H. These findings confirm the potential of modern deep-learning architectures in rainfall runoff modelling, but also highlight the noticeable differences between them in regard to the effect of calibration data length.
KW - Artificial neural networks
KW - Calibration
KW - Deep learning
KW - Rainfall-runoff
KW - modelling
Y1 - 2021
U6 - https://doi.org/10.1016/j.cageo.2021.104708
SN - 0098-3004
SN - 1873-7803
VL - 149
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Angeleska, Angela
A1 - Omranian, Sara
A1 - Nikoloski, Zoran
T1 - Coherent network partitions
BT - Characterizations with cographs and prime graphs
JF - Theoretical computer science : the journal of the EATCS
N2 - We continue to study coherent partitions of graphs whereby the vertex set is partitioned into subsets that induce biclique spanned subgraphs. The problem of identifying the minimum number of edges to obtain biclique spanned connected components (CNP), called the coherence number, is NP-hard even on bipartite graphs. Here, we propose a graph transformation geared towards obtaining an O (log n)-approximation algorithm for the CNP on a bipartite graph with n vertices. The transformation is inspired by a new characterization of biclique spanned subgraphs. In addition, we study coherent partitions on prime graphs, and show that finding coherent partitions reduces to the problem of finding coherent partitions in a prime graph. Therefore, these results provide future directions for approximation algorithms for the coherence number of a given graph.
KW - Graph partitions
KW - Network clustering
KW - Cographs
KW - Coherent partition
KW - Prime graphs
Y1 - 2021
U6 - https://doi.org/10.1016/j.tcs.2021.10.002
SN - 0304-3975
VL - 894
SP - 3
EP - 11
PB - Elsevier
CY - Amsterdam [u.a.]
ER -
TY - CHAP
A1 - Abramova, Olga
A1 - Gundlach, Jana
A1 - Bilda, Juliane
T1 - Understanding the role of newsfeed clutter in stereotype activation
BT - the case of Facebook
T2 - PACIS 2021 proceedings
N2 - Despite the phenomenal growth of Big Data Analytics in the last few years, little research is done to explicate the relationship between Big Data Analytics Capability (BDAC) and indirect strategic value derived from such digital capabilities. We attempt to address this gap by proposing a conceptual model of the BDAC - Innovation relationship using dynamic capability theory. The work expands on BDAC business value research and extends the nominal research done on BDAC – innovation. We focus on BDAC's relationship with different innovation objects, namely product, business process, and business model innovation, impacting all value chain activities. The insights gained will stimulate academic and practitioner interest in explicating strategic value generated from BDAC and serve as a framework for future research on the subject
Y1 - 2021
UR - https://aisel.aisnet.org/pacis2021/79
SN - 978-1-7336325-7-7
IS - 473
PB - AIS Electronic Library (AISeL)
CY - [Erscheinungsort nicht ermittelbar]
ER -
TY - CHAP
A1 - Abramova, Olga
A1 - Gladkaya, Margarita
A1 - Krasnova, Hanna
T1 - An unusual encounter with oneself
BT - exploring the impact of self-view on online meeting outcomes
T2 - ICIS 2021: IS and the future of work
N2 - Helping overcome distance, the use of videoconferencing tools has surged during the pandemic. To shed light on the consequences of videoconferencing at work, this study takes a granular look at the implications of the self-view feature for meeting outcomes. Building on self-awareness research and self-regulation theory, we argue that by heightening the state of self-awareness, self-view engagement depletes participants’ mental resources and thereby can undermine online meeting outcomes. Evaluation of our theoretical model on a sample of 179 employees reveals a nuanced picture. Self-view engagement while speaking and while listening is positively associated with self-awareness, which, in turn, is negatively associated with satisfaction with meeting process, perceived productivity, and meeting enjoyment. The criticality of the communication role is put forward: looking at self while listening to other attendees has a negative direct and indirect effect on meeting outcomes; however, looking at self while speaking produces equivocal effects.
Y1 - 2021
UR - https://aisel.aisnet.org/icis2021/is_future_work/is_future_work/16
PB - AIS Electronic Library (AISeL)
CY - [Erscheinungsort nicht ermittelbar]
ER -