Sebastian VanSyckel

A survey on engineering approaches for self-adaptive systems

The complexity of information systems is increasing in recent years, leading to increased effort for maintenance and configuration. Self-adaptive systems (SASs) address this issue. Due to new computing trends, such as pervasive computing, miniaturization of IT leads to mobile devices with the emerging need for context adaptation. Therefore, it is beneficial that devices are able to adapt context. Hence, we propose to extend the definition of SASs and include context adaptation. This paper presents a taxonomy of self-adaptation and a survey on engineering SASs. Based on the taxonomy and the survey, we motivate a new perspective on SAS including context adaptation.

Extending Context Management for Proactive Adaptation in Pervasive Environments

Proactive Adaptation enables application not only to react to changes in context, but to choose, whether they adapt themselves or the context based on context prediction. This can lead to more stable configurations and thus a higher user satisfaction. An integral part of proactive adaptation is context management. In contrast to reactive approaches that typically only read context information, proactive adaptation requires the integration of context manipulation via actuators. Further, the unsteady nature of predictions requires a form of notification. We present a comprehensive approach that offers both.

A survey of proactive pervasive computing

Pervasive computing applications are context-aware and adapt in order to cope with changes in their environment. In this, they should be as unobtrusive as possible. Proactive computing aims at acting on behalf of the user. Proactive adaptation allows to change the application and/or the context based on prediction. In this paper, we discuss and classify proactive pervasive computing research, as well as give an outlook on the field.

Tasklets: "Better than Best-Effort" Computing

The modern computing landscape consists of numerous heterogeneous devices, all of which can contribute to a distributed environment as generic computation resources. In unstructured environments, resources can easily be shared and consumed at the cost of certainty. While some applications can handle such a best-effort service, many others require execution qualities, e.g., reliability or speed. We introduce Quality of Computation (QoC) as a thin layer on top of uniformly abstracted best-effort resources, which allows to tailor computation tasks to application-specific needs. The QoC layer provides execution guarantees for reliability, speed, precision, privacy, cost, and energy. We demonstrate QoC on the basis of the Tasklet system. Tasklets are fine-grained units of computation that can be issued for local or remote execution. The Tasklet system has two layers. Below is the best-effort execution layer, a virtual machine that provides raw computation. Above is the orchestration layer, which federates these virtual machines to one distributed computing environment and enforces the mechanisms that guarantee the requested QoC. We evaluated the performance of QoC in the Tasklet system in various scenarios. Results indicate that our system provides QoC guarantees at minimal performance cost.

Configuration Management for Proactive Adaptation in Pervasive Environments

Pervasive computing applications have to adapt in order to cope with changes in their environment. Proactive adaptation allows to change the application and/ or the context based on prediction of context and user behavior, in order to reduce adaption delay and provide a seamless service to the user. Thus, such applications are self-organizing systems. Ideally, self-organizing systems adapt by changing their structure or behavior without requiring the users intervention. A prerequisite to that is the knowledge of the possible configurations and their order with respect to the suitability. We introduce a comprehensive framework based on an application model with suitability and cost metrics. Based on the application model, we construct a CSP and develop an algorithm with two heuristics that finds all configurations. We rate the configurations depending on their expected instantiation using novel utility and cost functions. In the evaluation, we show the feasibility of our approach.

COMITY: Coordinated application adaptation in multi-platform pervasive systems

Pervasive applications are designed to support users in their daily lives. In order to provide their services, these applications interact with the environment, i.e. their context. They either adapt themselves as a reaction to context changes, or adapt the context via actuators according to their needs. If multiple applications are executed in the same context, interferences are likely to occur. In this paper, we present COMITY-a framework for interference management in multi-platform pervasive systems. Based on contracts specifying an applications interaction with the context, the framework automatically detects interferences and resolves them through a coordinated application adaptation. We analyze the problem of interference resolution, discuss respective algorithms and extensively evaluate our prototype.

Towards Reusability in Autonomic Computing

Reusability of software artifacts reduces development time, effort, and error-proneness. Nevertheless, in the development of autonomic systems, developers often start from scratch when building a new system instead of reusing existing components. Many frameworks offer reusability on a higher level of abstraction, but neglect reusability on the lower component implementation level. In this short paper, we present a reusable adaptation logic by separating the generic structure and mechanisms of Autonomic Computing systems from its custom functionality. That is, we provide a reusable communication architecture with abstract component templates that enables a faster development and easier runtime adaptation. We evaluate our approach in a case study with two implementations.

COMITY: A framework for adaptation coordination in multi-platform pervasive systems

Pervasive applications are designed to support users in their daily lives. In order to provide their services, these applications interact with the environment, i.e., their context. They either adapt themselves as a reaction to context changes, or adapt the context via actuators according to their needs. If multiple applications are executed in the same context, interferences are likely to occur. In this paper, we present COMITY-a framework for interference management in multi-platform pervasive systems. Based on contracts specifying an applications interaction with the context, the framework automatically detects interferences and resolves them through a coordinated application adaptation.

FESAS: Towards a Framework for Engineering Self-Adaptive Systems

The complexity and size of information systems are growing, resulting in an increasing effort for maintenance. Self-adaptive systems (SAS) that autonomously adapt to changes in the environment or in the system itself (e.g. disfunction of components) can be a solution. So far, the development of SAS is frequently tailored to specific use case requirements. The creation of frameworks with reusable process elements and system components is often neglected. However, with such a framework developing SAS would become faster and less error prone. This work addresses this gap by providing a framework for engineering SAS.

Tasklets: Overcoming Heterogeneity in Distributed Computing Systems

Distributed computing is a good alternative to expensive supercomputers. There are plenty of frameworks that enable programmers to harvest remote computing power. However, until today, much computation power in the edges of the Internet remains unused. While idle devices could contribute to a distributed environment as generic computation resources, computation-intense applications could use this pool of resources to enhance their execution quality. In this paper, we identify heterogeneity as a major burden for distributed and edge computing. Heterogeneity is present in multiple forms. We draw our vision of a comprehensive distributed computing system and show where existing frameworks fall short in dealing with the heterogeneity of distributed computing. Afterwards, we present the Tasklet system, our approach for a distributed computing framework. Tasklets are fine-grained computation units that can be issued for remote and local execution. We tackle the different dimensions of heterogeneity and show how to make use of available computation power in edge resources. In our prototype, we use middleware and virtualization technologies as well as a host language concept.