Stefan Schulte

Stefan Schulte
Technische Universität Hamburg | TUHH · Institute of Data Engineering

Professor

About

175
Publications
77,628
Reads
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3,157
Citations
Additional affiliations
September 2021 - present
Technische Universität Hamburg
Position
  • Head of Department
March 2019 - August 2021
TU Wien
Position
  • Professor (Associate)
January 2015 - February 2019
TU Wien
Position
  • Professor (Assistant)
Education
February 2005 - November 2005
The University of Newcastle, Australia
Field of study
  • Information Technology
October 2001 - August 2006
Carl von Ossietzky Universität Oldenburg
Field of study
  • Computer Science
October 2000 - March 2006
Carl von Ossietzky Universität Oldenburg
Field of study
  • Economics (Major: Computer Science)

Publications

Publications (175)
Article
Business Process Management is a matter of great importance in different industries and application areas. In many cases, it involves the execution of resource-intensive tasks in terms of computing power such as CPU and RAM. Due to the emergence of Cloud computing, theoretically unlimited resources can be used for the enactment of business processe...
Article
The article is available here: http://authors.elsevier.com/a/1Qa4O_,OQCKOpe Abstract: With the advent of cloud computing, organizations are nowadays able to react rapidly to changing demands for computational resources. Not only individual applications can be hosted on virtual cloud infrastructures, but also complete business processes. This allow...
Article
With the Internet of Services, Web services from all areas of life and business will be offered to service consumers. Even though Web service technologies make it easy to consume services on arbitrary devices due to their platform-independence, service messaging is heavyweight. This may cause problems if services are invoked using devices with limi...
Conference Paper
Full-text available
Today's extensive business process landscapes make it necessary to handle the execution of a large number of workflows. Especially if workflow steps require the invocation of resource-intensive applications or a large number of applications needs to be carried out concurrently, process owners may have to allocate extensive computational resources,...
Article
Full-text available
Although virtual factories are a well-established approach to managing distributed, cross-organizational manufacturing processes, corresponding end-to-end IT support is still lacking. Service-oriented virtual factories use and extend well-known methods and technologies from service-oriented computing, the Internet of Things, and business process ma...
Preprint
Within this Technical Report, we present the full analysis of 61 routing protocols for Wireless Sensor Networks (WSNs) for the purposes of routing in Payment Channel Networks (PCNs). In addition, we present the full results of the implementation of the three algorithms E-TORA, TERP, and M-DART.
Article
Machine Learning (ML) is increasingly applied in industrial manufacturing, but often performance is limited due to insufficient training data. While ML models can benefit from collaboration, due to privacy concerns, individual manufacturers often cannot share data directly. Federated Learning (FL) enables collaborative training of ML models without...
Article
Based on the collective input of Dagstuhl Seminar (21342), this paper presents a comprehensive discussion on AI methods and capabilities in the context of edge computing, referred as Edge AI. In a nutshell, we envision Edge AI to provide adaptation for data-driven applications, enhance network and radio access, and allow the creation, optimization,...
Preprint
Full-text available
Based on the collective input of Dagstuhl Seminar (21342), this paper presents a comprehensive discussion on AI methods and capabilities in the context of edge computing, referred as Edge AI. In a nutshell, we envision Edge AI to provide adaptation for data-driven applications, enhance network and radio access, and allow the creation, optimization,...
Preprint
Today's blockchain landscape is severely fragmented as more and more heterogeneous blockchain platforms have been developed in recent years. These blockchain platforms are not able to interact with each other or with the outside world since only little emphasis is placed on the interoperability between them. Already proposed solutions for blockchai...
Chapter
Offloading of computation, e.g., to the cloud, is today a major task in distributed systems. Usually, consumers which apply offloading have to trust that a particular functionality offered by a service provider is delivering correct results. While redundancy (i.e., offloading a task to more than one service provider) or (partial) reprocessing help...
Preprint
Offloading of computation, e.g., to the cloud, is today a major task in distributed systems. Usually, consumers which apply offloading have to trust that a particular functionality offered by a service provider is delivering correct results. While redundancy (i.e., offloading a task to more than one service provider) or (partial) reprocessing help...
Article
Full-text available
Fog computing enables the execution of IoT applications on compute nodes which reside both in the cloud and at the edge of the network. To achieve this, most fog computing systems route the IoT data on a path which starts at the data source, and goes through various edge and cloud nodes. Each node on this path may accept the data if there are avail...
Article
Full-text available
Due to the proliferation of edge computing, cloud providers have started offering compute nodes at the edge of the network in addition to traditional compute nodes in data centers. So far, various systems have been proposed for processing Internet of Things (IoT) data on both edge and cloud compute nodes in order to reduce the communication latency...
Article
Full-text available
Recently, a multitude of conceptual architectures and theoretical foundations for fog computing have been proposed. Despite this, there is still a lack of concrete frameworks to setup real-world fog landscapes. In this work, we design and implement the fog computing framework FogFrame —a system able to manage and monitor edge and cloud resources in...
Article
Industry 4.0 will only become a reality through the convergence of Operational and Information Technologies (OT & IT), which use different computation and communication technologies. Cloud Computing cannot be used for OT involving industrial applications, since it cannot guarantee stringent non-functional requirements, e.g., dependability, trustwor...
Book
This book integrates the material of the lecture series “Blockchain and Robotic Process Automation”, offered at Kiel University. The lecture series sheds light on current research topics on blockchain and robotic process automation (RPA) also in combination with business process management (BPM) or process mining. In this series, leading scientists...
Article
Full-text available
Various performance benefits such as low latency and high bandwidth have turned fog computing into a well-accepted extension of the cloud computing paradigm. Many fog computing systems have been proposed so far, consisting of distributed compute nodes which are often organized hierarchically in layers. To achieve low latency, these systems commonly...
Preprint
Full-text available
In recent years, manifold blockchain protocols have been proposed by researchers and industrial companies alike. This has led to a very heterogeneous blockchain landscape. Accordingly, it would be desirable if blockchains could interact with each other. However, current blockchain technologies offer only limited support for interoperability, thus p...
Chapter
Federated Learning (FL) is a very promising approach for improving decentralized Machine Learning (ML) models by exchanging knowledge between participating clients without revealing private data. Nevertheless, FL is still not tailored to the industrial context as strong data similarity is assumed for all FL tasks. This is rarely the case in industr...
Preprint
Industry 4.0 will only become a reality through the convergence of Operational and Information Technologies (OT & IT), which use different computation and communication technologies. Cloud Computing cannot be used for OT involving industrial applications, since it cannot guar-antee stringent non-functional requirements, e.g., dependability, trustwo...
Article
Full-text available
As data collected and provided by Internet of Things (IoT) devices power an ever-growing number of applications and services, it is crucial that this data can be trusted. Data provenance solutions combined with blockchain technology are one way to make data more trustworthy by providing tamper-proof information about the origin and history of data...
Preprint
Full-text available
Federated Learning (FL) is a very promising approach for improving decentralized Machine Learning (ML) models by exchanging knowledge between participating clients without revealing private data. Nevertheless, FL is still not tailored to the industrial context as strong data similarity is assumed for all FL tasks. This is rarely the case in industr...
Conference Paper
Full-text available
Since the proliferation of fog computing, various distributed architectures have been proposed to extend the cloud to the edge of the network. However, so far there exists no study that compares different fog computing architectures, and produces quantitative results in order to examine the efficiency of each architecture for different use cases. S...
Preprint
Full-text available
Today, solutions for cross-blockchain asset transfers are either tailored for specific assets, require certain means of cross-blockchain communication, or neglect finality guarantees that prevent assets from getting lost in transit. In this paper, we present a cross-blockchain asset transfer protocol that supports arbitrary assets, is adaptable to...
Conference Paper
Full-text available
In recent years, the Internet of Things (IoT) has gained a lot of attention due to connecting various sensor devices with the cloud, in order to enable smart applications such as: smart traffic management, smart houses, and smart grids, among others. Due to the growing popularity of the IoT, the number of Internet-connected devices has increased si...
Chapter
Distributing data in a tamper-proof and traceable way is a necessity in many Internet of Things (IoT) scenarios. Blockchain technologies are frequently named as an approach to provide such functionality. Despite this, there is a lack of concrete solutions which integrate the IoT with the blockchain for data distribution purposes.
Preprint
Full-text available
Current blockchain technologies provide very limited means of interoperability. In particular, solutions enabling blockchains to verify the existence of data on other blockchains are either very costly or are not fully decentralized. To overcome these limitations, we introduce Testimonium, a novel blockchain relay scheme that applies a validation-o...
Research
Full-text available
Blockchain relay schemes offer the ability to verify transactions across blockchains in a decentralized manner. While this enables blockchain interoperability applications like cross-blockchain token transfers, relays can become expensive since state-of-the-art relays require every single block header of the source blockchain to be stored by the de...
Research
Full-text available
Blockchain relay schemes rely on off-chain clients constantly submitting block information from a source block-chain to the relay running on a destination blockchain. As clients incur costs when submitting block headers, an incentive structure needs to be in place that compensates clients for their efforts. In this paper, we develop an incentive st...
Conference Paper
As more and more applications and services depend on data collected and provided by Internet of Things (IoT) devices, it is of importance that such data can be trusted. Data provenance solutions together with blockchain technology are one way to make data more trustworthy. However, current solutions do not address the heterogeneous nature of IoT ap...
Conference Paper
Full-text available
Edge computing describes a paradigm for combining computational resources at the edge of the network with the cloud. Even though complementing the cloud with these resources provides benefits, e.g., low latency, it also introduces new challenges to the operational staff. Such challenges can be: deciding if the applications should be placed in the c...
Conference Paper
In recent years, distributed ledger technologies like blockchains have gained much popularity both within industry and research. Today, blockchains do not only act as the underlying technology for cryptocurrencies like Bitcoin, but have also been identified as a potentially disruptive technology in many different fields, e.g., supply chain tracking...
Research
Full-text available
Interoperability between blockchains remains an open problem with current interoperability approaches providing very limited means of cross-blockchain interaction. In particular, current solutions for cross-blockchain token transfers suffer from limitations such as excessive synchronization of any balance change across blockchains. To overcome thes...
Chapter
In recent years, distributed ledger technologies like blockchains have gained much popularity both within industry and research. Today, blockchains do not only act as the underlying technology for cryptocurrencies like Bitcoin, but have also been identified as a potentially disruptive technology in many different fields, e.g., supply chain tracking...
Article
Full-text available
Current blockchain technologies provide very limited interoperability. Restrictions with regard to asset transfers and data exchange between different blockchains reduce the usability and comfort of users, and hinder novel developments within the blockchain space. As a first step towards blockchain interoperability, we propose the DeXTT cross-block...
Article
Full-text available
In volatile data streams as encountered in the Internet of Things (IoT), the data volume to be processed changes permanently. Hence, to ensure timely data processing, there is a need to reconfigure the computational resources used for processing data streams. Up to now, mostly cloud-based computational resources are utilized for this. However, clou...
Conference Paper
Full-text available
Elastic data stream processing enables applications to query and analyze streams of real time data. This is commonly facilitated by processing the flow of the data streams using a collection of stream processing operators which are placed in the cloud. However, the cloud follows a centralized approach which is prone to high latency delay. For avoid...
Preprint
Current blockchain technologies provide very limited interoperability. Restrictions with regards to asset transfers and data exchange between different blockchains reduce usability and comfort for users, and hinder novel developments within the blockchain space. As a first step towards cross-blockchain interoperability, we propose the DeXTT cross-b...
Preprint
Full-text available
As more and more applications and services depend on data collected by Internet of Things (IoT) devices, it is of utmost importance that such data can be trusted. While data provenance solutions together with blockchain technology are one way to make data more trustworthy, current solutions do not address the heterogeneous nature of IoT application...
Preprint
Full-text available
The suitability of a particular blockchain for a given use case depends mainly on the blockchain's functional and non-functional properties. Such properties may vary over time, and thus, a selected blockchain may become unsuitable for a given use case. This uncertainty may hinder the widespread adoption of blockchain technologies in general. To mit...
Research
Full-text available
Interoperability between blockchains remains an open problem, with current interoperability approaches providing very limited means of cross-blockchain interaction, mostly in the form of atomic swaps. More general means of blockchain in-teroperability such as cross-blockchain data exchange, including cross-blockchain token transfer would contribute...
Article
Business Process Management Systems (BPMS) need to be able to take into account the fluctuating demand for computational resources during the execution of business process activities. Today, BPMS rely on the leasing and releasing of virtual machines (VMs) on cloud resources, which leads to a rather coarse-grained allocation of computational resourc...
Conference Paper
Stream processing systems are able to integrate data from various sources, and to invoke self-hosted and external operators. In case of faults, such systems usually rely on the redundancy of single stream processing operators, while the relationship between the single operators is not taken into account. Hence, there is a lack of approaches towards...
Research
Full-text available
Interoperability between blockchains remains an open problem, with current approaches providing very limited means of cross-blockchain interaction, mostly in the form of atomic swaps. However, very little means of cross-blockchain data exchange, including cross-blockchain token transfers, are found in literature. To address this issue, within the T...
Article
Full-text available
Elastic distributed stream processing systems are able to dynamically adapt to changes in the workload. Often, these systems react to the rate of incoming data, or to the level of resource utilization, by scaling up or down. The goal is to optimize the system's resource usage, thereby reducing its operational cost. However, such scaling operations...
Research
Full-text available
Technologies enabling interoperability across blockchains have recently gained much popularity in science and industry. Cross-blockchain asset transfers are one particular use case which has been proposed to foster such interoperability. In previous work, we have presented the concept of claim-first transactions as a method of transferring assets f...
Technical Report
Full-text available
In software testing, verification of a system's dynamic properties such as auto-scaling behavior can be vital for a project's success. However, testing such properties can be difficult when parts of the system are not implemented yet, mocked or simply not available, as those parts might have a great impact on the system's runtime behavior. To addre...
Chapter
A key challenge for elastic business processes is the resource-efficient scheduling of cloud resources in such a way that Quality-of-Service levels are met. So far, this has been difficult, since existing approaches use a coarse-granular resource allocation based on virtual machines.
Conference Paper
Full-text available
Fog computing provides a paradigm for executing Internet of Things services. Enabling the coordinated cooperation among computational, storage, and networking resources in the fog can be challenging due to the volatility of resources. For this reason, we design an architecture and implement a representative framework called FogFrame that defines th...
Conference Paper
Full-text available
In cloud computing, detecting violations of Service Level Agreements (SLAs) is possible by measuring certain metrics, which can be done by both the provider and the consumer of a service. However, both parties have contradicting interests with regards to these measurements, which makes it difficult to reach consensus about whether SLA violations ha...
Research
Full-text available
Cryptocurrencies share a broad overall purpose, enabling distributed, decentralized and trustless transfers of value. Nevertheless, the various blockchains upon which each cryptocurrency is implemented remain, for the most part, unconnected. While approaches for atomic swaps (the secure exchange of tokens on one chain for another) are emerging, the...
Research
Full-text available
Blockchains, the fundamental technology upon which cryptocurrencies are implemented, have gained considerable interest in finance, economics, and research. Nevertheless, the numerous blockchains in existence remain mostly unconnected, with no possibilities for interoperability. While approaches for atomic swaps (the atomic exchange of value on two...
Article
Agile business networking is an emerging concept aimed at helping companies face the challenges of the dynamic economy of the 21st century. It integrates a technology and a business perspective, arriving at highly dynamic Internet-based processes. Despite its importance, there is no common understanding of this concept; many interpretations exist,...
Conference Paper
Full-text available
The continuing growth of the Internet of Things (IoT) requires established stream processing engines (SPEs) to cope with new challenges, like the geographic distribution of IoT sensors and clouds hosting the SPEs. These challenges obligate SPEs to support distributed stream processing across different geographic locations which also require a new a...
Article
Full-text available
(Note that we have updated the paper to the accepted version on 23 Jan 2018) Blockchain technology offers a sizable promise to rethink the way inter-organizational business processes are managed because of its potential to realize execution with- out a central party serving as a single point of trust (and failure). To stimulate research on this pro...