Christoph Meinel

Christoph Meinel
Hasso Plattner Institute · Research Group Internet Technologies and Systems

Professor Dr. sc. nat Dr. rer. nat

About

1,428
Publications
250,856
Reads
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13,342
Citations

Publications

Publications (1,428)
Conference Paper
Massive Open Online Courses (MOOCs) are usually attended by several thousand learners who barely get to know each other during the course runtime. Being unaware of fellow learners often results in a low sense of community. In addition, many MOOC learners are afraid of using the course forum, which is often the only offered possibility to participat...
Conference Paper
While derived from software engineering, “agile” has become increasingly sought-after among public sector organisations in the last decade (more so during the global pandemic) as the means to become more responsive, flexible, adaptive, and rapid in their behaviour. However, there is a limited understanding with regard to two important and related t...
Conference Paper
Design-led approaches to public service provision promise to reduce costs, improve efficiency, increase user-centricity and enhance the overall quality of services. Despite advances in the field of design thinking, too often, we witness a rather uncritical appraisal of design and design thinking without serious attention directed at understanding i...
Conference Paper
Massive Open Online Courses (MOOCs) have become a well-established tool for lifelong learning since their first invention in 2008. Although the courses initially aimed at high social interaction rates and interactive course structures, most conducted courses since the big MOOC hype in 2012 follow a classic teaching approach that often lacks interac...
Preprint
Full-text available
The challenging field of scene text detection requires complex data annotation, which is time-consuming and expensive. Techniques, such as weak supervision, can reduce the amount of data needed. In this paper we propose a weak supervision method for scene text detection, which makes use of reinforcement learning (RL). The reward received by the RL...
Chapter
Since the start of the pandemic in March 2020 at the latest, e-learning has become a key factor. Many students and teachers had to shift from a traditional campus to online platforms and learn new skills in a very short time. Even before the pandemic, lack of technical skills, poor hardware, and unstable internet connections were not the only limit...
Chapter
With the proliferation of mobile devices in daily lives, users access Massive Open Online Courses (MOOCs) more often with devices other than stationary desktop computers. The introduction of mobile applications for MOOC platforms improved the learning experience by enabling Internet-independent learning sessions. Despite the university-like setting...
Preprint
Full-text available
Contrastive Language--Image Pre-training (CLIP) has shown remarkable success in learning with cross-modal supervision from extensive amounts of image--text pairs collected online. Thus far, the effectiveness of CLIP has been investigated primarily in general-domain multimodal problems. This work evaluates the effectiveness of CLIP for the task of M...
Conference Paper
Full-text available
The current Self-Sovereign Identity (SSI) ecosystem is rapidly changing and ill-defined. Manifold actors, projects, and initiatives produce different SSI solutions, frameworks, protocols, and distributed ledgers. Even though some patterns exist among SSI ecosystem members, no elaborate systematization has been made. This paper conducts a systematic...
Conference Paper
Full-text available
The digital transformation of public organizations reached a new level during the COVID-19 global pandemic. The delivery of public services leveraged on digital technologies to ensure the continuity of the service. Despite the advances in digital government, little is known about the opportunities and risks posed by such quick responses during the...
Article
Full-text available
Live migration is an essential feature in virtual infrastructure and cloud computing datacenters. Using live migration, virtual machines can be online migrated from a physical machine to another with negligible service interruption. Load balance, power saving, dynamic resource allocation, and high availability algorithms in virtual data-centers and...
Conference Paper
Social media has become a popular communication platform on which shared content such as images form a large part of the communicated data. Yet, shared images can reveal sensitive information in the sense that the data after its publication remains accessible. Existing studies provide mechanisms to modify co-owned images for user privacy but requir...
Chapter
Zu jeder Webadresse muss die passende IP-Adresse gefunden werden. Das ist ein immenser Aufwand – nur gut, dass die Last auf viele Schultern verteilt werden kann.
Chapter
Eine fundamental neue Welt eröffnen uns die großen Digitalunternehmen. Doch wie wir am Ende darin leben wollen, das hängt vor allem von uns selbst ab.
Chapter
Für uns Nutzer wirkt es, als verstünde jeder Rechner jeden anderen im Internet. Tatsächlich ist dies jedoch nur dank ausgefeilter Übersetzungsprogramme möglich: dem Internetworking.
Chapter
Das Internet wurde 1969 im Jahr der Mondlandung erfunden. Eigentlich ganz passend: In beiden Fällen ließ die Menschheit die alte Welt hinter sich.
Chapter
In der analogen Welt gibt es unendlich viele Formen, Farben und Gestalten. Im Digitalen gibt es nur Nullen undEinsen. Wie erreicht man, dass beides zusammenfindet?
Chapter
Ein Video ist nichts anderes als eine gewaltige Folge von Bildern. Um die im Internet zu übertragen, braucht es Komprimierungen, die die Datenmengen auf ein handhabbares Maß reduzieren.
Chapter
Webservices schaffen die Basis, dass sich Maschinen über das Netz finden und verknüpfen können.
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Das eine große Internet gibt es in Wirklichkeit gar nicht. Damit aber die Illusion eines solchen entsteht, braucht es mit viel Technik zum Netzwerken.
Chapter
Dank TCP/IP funktioniert das Internetworking. Aber wie können Anwendungen das Internet nutzen? Es braucht ein weiteres entscheidendes Element.
Chapter
Um einen reibungslosen Versand der Informationen zu gewährleisten, arbeitet das Internet in Schichten: Alles Notwendige regeln clever konstruierte und aufeinander abgestimmte Kommunikationsprotokolle.
Chapter
Zum ruckelfreien Streamen braucht es mehr als nur eine schnelle Internetverbindung. Erst weitere Innovationen machen die Allgegenwart von Onlinevideos möglich.
Chapter
Damit Texte, Bilder oder Videos ins Digitale gelangen, braucht es eine Übersetzung mit der richtigen Kodierung. Aber der Benutzer soll davon nichts mitbekommen.
Chapter
Mit dem neuen Internetstandard ist Sparsamkeit passé: Dank IPv6 gibt es Adressen in Hülle und Fülle. Diese sind allerdings deutlich komplexer.
Chapter
Tagtäglich werden hunderte Milliarden E-Mails über das Internet versandt. Doch was läuft hinter den Kulissen ab, wenn Sie auf „Senden” drücken?
Chapter
Doch TCP macht noch viel mehr: Es verhindert, dass unser Internet im Dauerstau versinkt.
Chapter
Nur mit HTTP ist das WWW kein WWW, so viel ist sicher. Cookies helfen beim flüssigen Weberlebnis, aber es braucht auch eine digitale Grundhygiene.
Chapter
Webseitennamen versteht der Mensch, IP-Adressen der Computer. Ein Glück nur, dass es einen Dolmetscher gibt. Das Domain Name System macht es möglich.
Chapter
Für den normalen Datenverkehr im Netz ist Sorgfalt oberstes Gebot. Modernes Streaming ist dafür aber zu ungeduldig. Hier schlägt die Stunde von UDP.
Chapter
Was das Einschreiben mit Rückschein für den Briefeschreiber ist, ist im Internet das TCP-Protokoll. Es stellt sicher, dass die Sendung nicht verloren geht.
Chapter
Das Erstaunliche: Die Standards des Internets entwickelten sich entlang der Nutzererfahrung und ohne Oberaufsicht. Trotzdem funktioniert es. Wie geht das?
Chapter
Im Internet werden heute Daten in gigantischem Ausmaß transportiert. Ein Glück, dass man an strategischen Stellen Depots anlegen kann: Caches verhindern überflüssige Datenbewegungen.
Chapter
Bei der Nutzung des Webs hinterlassen wir überall Datenspuren, die fleißige Datensammler registrieren und weitergeben. Schlimm ist, wenn das hinter dem Rücken der Nutzer passiert.
Chapter
Im Grunde ist ein WLAN ein LAN ohne Kabel. Doch der Teufel steckt im Detail. Wie wird verhindert, dass alle gleichzeitig reden und keiner mehr zuhören kann?
Chapter
E-Mails zu versenden, ist eine der ersten Anwendungen im Internet. Aber erst dank neuer Standards und Protokolle können wir sie so bequem und bunt nutzen.
Chapter
Von Cookies bis Caching – dank zahlreicher Schlüssel-innovationen wird das WWW zur Killer-App des Internet
Chapter
Das Internet verdankt seinen Erfolg wohl auch der Tatsache, dass niemand an den Hebeln der Macht sitzt. Das Internet wird von einer ganzen Reihe internationaler Organisationen gestaltet.
Chapter
Mit mehr IP-Adressen, als es Sterne im Universum gibt, hat das Internet endlich den Raum, den es zu seiner Entfaltung braucht. Noch aber hakt es beim Aufbruch in die endlosen Weiten.
Chapter
Am Anfang war das Web eine Einbahnstraße, doch dann kam plötzlich Gegenverkehr auf. Wie funktioniert das, dass jeder mitmachen kann im Web?
Chapter
Was das Internet angeht, leben wir noch in einem ganz frühen Stadium: in einer Welt voller Rätsel, Mythen und Überraschungen. Es ist Zeit, das zu ändern.
Chapter
Sockets und Ports verbinden Anwendungen auf Computern im Internet, ähnlich wie Häfen in der analogen Welt, die dafür sorgen, dass Waren zielgerichtet verladen und weitertransportiert werden.
Chapter
Suchmaschinen weisen uns in den Weg im riesigen Web-Kosmos. Blitzschnell finden sie, was wir suchen. Ohne sie wären wir im Web hoffnungslos verloren.
Chapter
Weitverkehrsnetzwerke bestehen aus Millionen verteilter Netzknoten. Aber eine genaue Karte ihres Aufbaus gibt es nicht. Wie kommt die Information trotzdem ans Ziel?
Chapter
Eigentlich sind Töne nur Druckschwankungen in der Luft. Damit der Computer damit etwas anfangen kann, muss das in Binärkodierung übersetzt werden.
Chapter
Zig Milliarden Internetcomputer gibt es, jeder davon mit eigener Adresse. Das raffinierte Verfahren, das hier den Überblick behielt, wurde inzwischen Opfer seines Erfolgs.
Chapter
Kaum ein Rechner steht noch für sich. Wie gelingt es, tausende davon zu einem großen Netzwerk zusammenzuschließen? Die LAN-Technologie macht es möglich.
Chapter
Ein Web, das seine Inhalte versteht, wird der nächste große Entwicklungsschritt. Ansätze dafür gibt es bereits.
Chapter
Von diesen Protokollen und Beschreibungssprachen bekommt man als Nutzer kaum etwas mit. Dabei sind sie die Grundfesten des Web.
Chapter
„Smart” ist heute nicht mehr nur das -phone. Maschinen untereinander digital zu verknüpfen, wird die Welt weiter transformieren.
Chapter
Innovation is the only way the EU can maintain a strong, sustainable and competitive economy. However, at present there are large imbalances between degrees of innovation of EU countries. Statistics of 2018 and 2019 classify Romania as the least innovative country of EU. One solution to mitigate this drawback consists of development of collaborativ...
Conference Paper
Traditional (online) teaching approaches put the student into a video-based, classroom-like situation. When asked to reproduce the content, the student can consciously remember what he learned and answer accordingly. Contrasting, knowledge of IT-security aspects requires sensitization for the topic throughout the daily life of a learner. We learned...
Chapter
Within today’s organizations, a Security Information and Event Management (SIEM) system is the centralized repository expected to aggregate all security-relevant data. While the primary purpose of SIEM solutions has been regulatory compliance, more and more organizations recognize the value of these systems for threat detection due to their holisti...
Conference Paper
Learning a programming language requires learners to write code themselves, execute their programs interactively, and receive feedback about the correctness of their code. Many approaches with so-called auto-graders exist to grade students' submissions and provide feedback for them automatically. University classes with hundreds of students or Mass...
Article
Full-text available
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...
Conference Paper
Im Zuge des zweiten Universitätssemesters unter Pandemiebedingungen war nicht nur die Durchführung von digitalen Veranstaltungen eine Hürde, sondern auch die Frage nach den Prüfungen und Klausuren. Losgelöst von Institut, Fachbereich und Standort mussten Lehrende eine Antwort auf technische, organisatorische und rechtliche Fragen finden. Die vorlie...
Chapter
Text style transfer task is transferring sentences to other styles while preserving the semantics as much as possible. In this work, we study a two-step text style transfer method on non-parallel datasets. In the first step, the style-relevant words are detected and deleted from the sentences in the source style corpus. In the second step, the rema...
Conference Paper
Full-text available
The world is experiencing remote interaction in unprecedented frequency, as people stay in touch and work together remotely in pandemic times. IT solutions for remote work such as videoconferencing systems have received a lot of critical attention as they seem to induce fatigue. By contrast, in online video games, people collaborate passionately an...
Chapter
Full-text available
Empathy is a central concept in design thinking. According to human-centred design, developers of novel products shall strive for a good understanding of product users, in order to design for their needs. This requires sophisticated cognitive capacities on behalf of the designers: being able to distinguish between their own knowledge states and nee...
Chapter
Design Thinking is a human-centered approach to innovation that has become increasingly popular globally over the last decade. While the spread of Design Thinking is well understood and documented in Europe and North America, this is not the case when it comes to the Arab world. This study explores the history, application, and understanding of Des...
Preprint
One of the most pressing problems in the automated analysis of historical documents is the availability of annotated training data. In this paper, we propose a novel method for the synthesis of training data for semantic segmentation of document images. We utilize clusters found in intermediate features of a StyleGAN generator for the synthesis of...
Book
Full-text available
Conference proceeding of the EMOCs 2021 confernce in Potsdam (Germany)
Conference Paper
As the Internet becomes more ubiquitous, everyone could access the data and services anytime, anywhere. However, it raises the challenge to enforce physical access control for the data or services to only be accessed in specific locations. Location-based access control (LBAC) systems could provide physical access control by only authorizing access...
Conference Paper
Full-text available
Online learning environments, such as Massive Open Online Courses (MOOCs), often rely on videos as a major component to convey knowledge. However, these videos exclude potential participants who do not understand the lecturer’s language, regardless of whether that is due to language unfamiliarity or aural handicaps. Subtitles and/or interactive tra...
Conference Paper
Since the start of the pandemic in March 2020 at the latest, e-learning has become a key factor. Many students and teachers had to shift from a traditional campus to online platforms and learn new skills in a very short time. Even before the pandemic, lack of technical skills, poor hardware, and unstable internet connections were not the only limit...
Preprint
Recent works on Binary Neural Networks (BNNs) have made promising progress in narrowing the accuracy gap of BNNs to their 32-bit counterparts. However, the accuracy gains are often based on specialized model designs using additional 32-bit components. Furthermore, almost all previous BNNs use 32-bit for feature maps and the shortcuts enclosing the...
Conference Paper
Learners in Massive Open Online Courses offering practical programming exercises face additional challenges next to the actual course content. Beginners have to find approaches to deal with misconceptions and often struggle with the correct syntax while solving the exercises. The paper at hand presents insights from offering contextual tips in a we...
Conference Paper
Students can use personal mobile devices to access Massive Open Online Courses (MOOCs) in addition to desktop comput- ers. However, user interfaces are often only scaled to smaller screen sizes and interaction patterns of a desktop learning experience do not always fit well with the characteristics of mobile devices. Adequate solutions for answerin...
Data
In this video presentation, we shortly introduce our work on contextual tips for auto-gradable programming exercises in Massive Open Online Courses (MOOCs). We measured the effects of our approach in a Python course with over 6,000 active students in a hidden A/B test and additionally used qualitative surveys. While the majority of learners valued...
Conference Paper
PURPOSE: This study investigates the link between employees' Job Insecurity (JI) and Innovation Behavior (IB) while considering a moderation effect of Organizational Support, Participative Decision Making, and Job Autonomy. The findings of this study can help organizations maneuver through difficult times of downsizing, restructuring and organizati...
Chapter
Online services fundamentally rely on identity management to secure and personalize their presence. Within identity management, attribute assurance techniques target correctness and validity of attributes. These properties are an essential foundation for service provisioning in digital businesses. A myriad of attribute assurance trust models has be...
Chapter
Sequencing genomes and analysing their variations can make an essential contribution to healthcare research on drug discovery and advancing clinical care, for instance. Genome sequencing data, however, presents a special case of highly sparsely populated, multi-attribute, high-dimensional data, in which each record (tuple) can be associated with mo...
Chapter
With more cloud customers are storing their data in multiple Cloud Service Providers (CSPs), they are responsible for managing the data in the multi-cloud storage environment, including monitoring the events on the cloud. They could monitor various cloud storage services by collecting, processing, and analyzing the cloud storage log files generated...
Chapter
Determining unique attribute combinations as quasi-identifiers is a common starting point for both re-identification attacks and data anonymisation schemes. The efficient discovery of those quasi-identifiers (QIDs) has been a combinatoric nightmare, actually an enumeration problem [1–3] given its W2-complete nature [4–6]. Proper privacy guarantees...
Chapter
An alternative to passwords for the verification of a user’s identity is authentication based on behavioural biometrics such as gait-based verification. To have good classification performances, knowledge of the specific activity or location while walking is required. In the related discipline of Human Activity Recognition, much work has been done...
Chapter
With his treatise “Experiences in Visual Thinking” first published in 1972, McKim delivers a milestone in the development of design thinking theory and practice. Building on creative thinking theories advanced by John E. Arnold before, McKim develops a comprehensive framework of creativity as embodied and embedded cognition. He elaborates on the ro...
Chapter
Neurodesign is a novel field of research, education and practice that emerges as a cross-disciplinary initiative. In 2019, the Hasso Plattner Institute (HPI) offered for the first time a neurodesign curriculum. The objective of neurodesign as we pursue it is to explore synergies at the intersection of (i) neuroscience, (ii) engineering and (iii) de...
Chapter
Massive Open Online Course (MOOC) instructors often use written discussion forum posts to initiate the course and to onboard their learners. To improve and expand on this practice, we adapted “warm-up games” from the context of design thinking and improvisational theatre to the discussion forum format of three MOOCs. In this chapter we describe how...
Chapter
Full-text available
Live migration is an essential feature in virtual infrastructure and cloud computing datacenters. Using live migration, virtual machines can be online migrated from a physical machine to another with negligible service interruption. Load balance, power saving, dynamic resource allocation, and high availability algorithms in virtual data-centers and...
Preprint
Full-text available
The analysis of the compression effects in generative adversarial networks (GANs) after training, i.e. without any fine-tuning, remains an unstudied, albeit important, topic with the increasing trend of their computation and memory requirements. While existing works discuss the difficulty of compressing GANs during training, requiring novel methods...
Conference Paper
The Hasso Plattner Institute (HPI) successfully operates a MOOC (Massive Open Online Course) platform since 2012. Since 2013, global enterprises, international organizations, governments, and research projects funded by the German ministry of education are partnering with us to operate their own instances of the platform. The focus of our platform...
Chapter
Digitized archives contain and preserve the knowledge of generations of scholars in millions of documents. The size of these archives calls for automatic analysis since a manual analysis by specialists is often too expensive. In this paper, we focus on the analysis of handwriting in scanned documents from the art-historic archive of the Wildenstein...
Chapter
Now we are ready to go deeper into the subject matter, and you have a chance to form a first opinion about blockchain technology – is it an innovation or only hype? Thereby, we will take a closer look at the architecture of blockchain technology using well-known examples such as Bitcoin and Ethereum and addressing challenges including security and...
Chapter
What kind of problems can blockchain technology solve as an “ultimate” technology? Taking a sober look at a new technology is the basis for its potentially successful use. We would therefore like to concentrate on the innovation of blockchain technology and consider the advantages that this technology offers us when compared to already existing sol...
Chapter
The context for the subject of blockchain has now been established. Some readers perhaps may not have a technical background to allow for a complete understanding of the entire mechanism of blockchain technology. In this chapter, we would like to take a closer look at the individual approaches that make up blockchain technology and how they are com...
Chapter
Our digital and geographically distributed society faces great challenges nowadays in managing communication between people—who in most cases—have never met each other before. This is particularly relevant for institutions working with peers that interact in remote environments where team collaboration is an essential driver of strategic innovation...
Chapter
For a better idea of which applications are possible based on blockchain technology, or which areas can profit from this technology, we will look at already existing blockchain projects. We ask you to note that the projects or companies mentioned in this chapter serve only to illustrate ideas and possible implementations.
Chapter
We now know about the basic challenges facing the secure use of decentralized systems, and, by way of an example, have seen what has made blockchain technology possible. Before we dive deeper into the subject matter, we will attempt to gain a better understanding of blockchain technology by way of a previous example. We also want to draw a demarcat...
Book
This book focuses on the innovation of blockchain technology and the advantages it offers. It provides a clear and comprehensive overview of blockchain technology and its possibilities, and thereby helps readers to form an opinion and draw their own conclusions about its potential exploitations. The book begins with a chapter on the topic of decent...