Torben Weis

Requirements of Peer-to-Peer-based Massively Multiplayer Online Gaming

Massively multiplayer online games have become increasingly popular. However, their operation is costly, as game servers must be maintained. To reduce these costs, we aim at providing a communication engine to develop massively multiplayer online games based on a peer-to-peer system. In this paper we analyze the requirements of such a system and present an overview of our current work.

Rapid Prototyping for Pervasive Applications

VisualRDK is a high-level programming language for prototyping pervasive applications. Context is tightly integrated into the language itself, so developers can attach functionality to locations, persons, or situations instead of the device. Pervasive computing appliances range from consumer devices over embedded sensor boards to PCs and large-scale context servers. Because these devices vary tremendously in their capabilities, application developers must create different programming models for every class of device. This makes rapid prototyping infeasible as soon as more than one class of devices is involved. Rapid prototyping therefore requires a programming model that hides the environments heterogeneity.

Model metamorphosis

Model driven architectures (MDA) will become practical only if transformations from platform-independent to platform-specific models can be largely automated. Kafka, an extensible rule-based transformation language, and the Kase modeling tool enable automated, customized transformations that support round-trip engineering. With Kafka and Kase, developers can construct transformations without detailed knowledge of metamodels.

Self-stabilizing publish/subscribe systems: algorithms and evaluation

Most research in the area of publish/subscribe systems has not considered fault-tolerance as a central design issues. However, faults do obviously occur and masking all faults is at least expensive if not impossible. A potential alternative (or sensible supplementation) to fault masking is self-stabilization which allows a system to recover from arbitrary transient faults such as memory perturbations, communication errors, and process crashes with subsequent recoveries. n nIn this paper we discuss how publish/subscribe systems can be made self-stabilizing by using self-stabilizing content-based routing. When the time between consecutive faults is long enough, corrupted parts of the routing tables are removed, while correct parts are refreshed in time, and missing parts are inserted. To judge the efficiency of self-stabilizing content-based routing, we compare it to flooding, which is the naive implementation of a self-stabilizing publish/subscribe system. We show that our approach is superior to flooding for a large range of practical settings.

Optimizing locality for self-organizing context-based systems

Running context-based systems with a fixed infrastructure involves substantial investments. There have been efforts to replace those systems with self-organizing ones. Therefore, recent systems use peer-to-peer (P2P) technology as a basis. Context-information is bound to a specific location and thus should be stored on a nearby node. Common P2P algorithms use one-dimensional ID spaces. However, locations have at least two coordinates, namely x and y. We use space-filling curves to map the two-dimensional area onto the one-dimensional ID space. In this paper we discuss the suitability of different space-filling curves for the average case and for stochastic scenarios.

Customizable pervasive applications

Human behavior and housing resist every standardization effort. Many aspects such as different technical equipment, furniture, and usage patterns make our surroundings as individual as ourselves. Thus, the personalization of pervasive applications is a fundamental requirement. To enable the development of custom pervasive applications, we propose a software development process. This process is based on the successful process for modern desktop applications. There, developers create extensible applications and components. Customizers use the resulting artifacts to develop custom applications. Finally, users configure applications to their individual needs by adjusting predefined settings. To adopt this process for pervasive computing, we present a component system for developers, a graphical toolkit for customizers, and self-configuration algorithms to ease the deployment

Quality of service in middleware and applications: a model-driven approach

Quality of service (QoS) management has become an important requirement for middleware platforms and distributed applications. Early QoS engineering attempts focused on single-category extensions to standard middleware. In recent years generic middleware frameworks have been proposed in order to facilitate multicategory QoS management. Our experience with such a framework has revealed that QoS management cannot be shielded from the applications. Applications need to be designed in a QoS-aware manner and application QoS requirements need to be translated into appropriate middleware extensions. Therefore we propose a comprehensive, model-driven development process for QoS-enabled distributed applications on top of QoS-enhanced middleware platforms. Our approach builds on OMGs Model-Driven Architecture (MDA). We demonstrate the mapping from the platform-independent to the platform-specific model, and we show how the design approach is applied targeting a .NET-based QoS-enabled middleware.

The Internet of Things - Context-based Device Federations

Locating physical devices and accessing their functionality in pervasive environments is strongly restricted by their locality. Since there are more and more devices available, waiting to serve users, a simple way is required to access, connect, and most important to locate them in the real world. In this paper we propose an approach to connect and access arbitrary devices by federating them related to their geographical location. This approach allows us to create context-aware federations of devices - the Internet of things

Scripting your home

Our homes and lives are as individual as ourselves. Many aspects, such as technical equipment, furniture, and usage patterns in these surroundings differ. Thus, personalization of applications that operate in such environments is required. The challenge for tools and programming paradigms is to provide a powerful but yet easy-to-use platform. In this paper we illustrate how our visual scripting language puts these requirements for programming ubiquitous computing environments into action.

Self-organizing and self-stabilizing role assignment in sensor/actuator networks

Developing distributed applications for sensor/actuator networks is challenging, particularly, with regard to unreliable nodes and communication links Splitting applications into roles eases the development significantly but presumes a reliable role management that autonomously assigns roles to devices depending on their capabilities In this paper, we present a self-organizing and self-stabilizing role assignment mechanism as an integral part of a light-weight, flexible middleware The deployed algorithms tolerate the addition and removal of devices at runtime and are also able to recover from any transient fault Considering that resources are restricted on many devices, we analyze the proposed algorithms with respect to communication overhead, memory usage, and stabilization time.