Browsing by Author "Müller, Christian"

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Open Access
Automated data validation in model-driven IoT applications
(2023) Müller, Christian
Building large IoT applications using a model-driven approach, has become an important methodology for building such applications. A tool intended to help with this process is the IoT Application Modelling tool developed at the University of Stuttgart. However, this tool is lacking validation capabilities. To implement validation in a (semi) automated manner, this work proposes an approach to assist the modeller with the task of selecting the best suited outlier detection method for a context model. based on existing or accumulated data. To achieve this a semi-automated wizard, integrated into the IoT Application Modelling Tool is proposed. Furthermore, concepts on how the resulting outlier detection can be deployed on the IoT infrastructure are discussed. The provided value and the usability of the tool are evaluated using a survey on a small set of researchers and IT professionals. The result of this survey have shown, that the proposed approach does partially automate and simplify the process of choosing an machine-learning based outlier detection method.
Open Access
Practical aspects of FaaS applications' migration
(2019) Müller, Christian
With the huge variety of available FaaS platforms in cloud and self-hosted environments the idea of migrating function applications from one provider to another is becoming a important consideration. This work investigates the challenges developers encounter when manually migrating applications between Amazon Web Services, Microsoft Azure and IBM Cloud regarding the efforts needed to migrate the functions and the services. This work also proposes a simple approach to reduce the coupling between the function application and the cloud provider by externalizing the business logic into a serparate, completely vendor independant, package. We see that this approach reduces the efforts needed to migrate the source code to another provider but it does not reduce the effort of migrating the functions configuration and services. We see that the efforts for migration are not only affected by the migration of the source code but also by the migration of the services, especially in self-hosted environments. There developers also have to find a proper substitution of the service for their use-case.