Distributed Real-time Systems - Deterministic Protocols for Wireless Networks and Model-Driven Development with SDL

In a networked system, the communication system is indispensable but often the weakest link w.r.t. performance and reliability. This, particularly, holds for wireless communication systems, where the error- and interference-prone medium and the character of network topologies implicate special challenges. However, there are many scenarios of wireless networks, in which a certain quality-of-service has to be provided despite these conditions. In this regard, distributed real-time systems, whose realization by wireless multi-hop networks becomes increasingly popular, are a particular challenge. For such systems, it is of crucial importance that communication protocols are deterministic and come with the required amount of efficiency and predictability, while additionally considering scarce hardware resources that are a major limiting factor of wireless sensor nodes. This, in turn, does not only place demands on the behavior of a protocol but also on its implementation, which has to comply with timing and resource constraints. The first part of this thesis presents a deterministic protocol for wireless multi-hop networks with time-critical behavior. The protocol is referred to as Arbitrating and Cooperative Transfer Protocol (ACTP), and is an instance of a binary countdown protocol. It enables the reliable transfer of bit sequences of adjustable length and deterministically resolves contest among nodes based on a flexible priority assignment, with constant delays, and within configurable arbitration radii. The protocol's key requirement is the collision-resistant encoding of bits, which is achieved by the incorporation of black bursts. Besides revisiting black bursts and proposing measures to optimize their detection, robustness, and implementation on wireless sensor nodes, the first part of this thesis presents the mode of operation and time behavior of ACTP. In addition, possible applications of ACTP are illustrated, presenting solutions to well-known problems of distributed systems like leader election and data dissemination. Furthermore, results of experimental evaluations with customary wireless transceivers are outlined to provide evidence of the protocol's implementability and benefits. In the second part of this thesis, the focus is shifted from concrete deterministic protocols to their model-driven development with the Specification and Description Language (SDL). Though SDL is well-established in the domain of telecommunication and distributed systems, the predictability of its implementations is often insufficient as previous projects have shown. To increase this predictability and to improve SDL's applicability to time-critical systems, real-time tasks, an approved concept in the design of real-time systems, are transferred to SDL and extended to cover node-spanning system tasks. In this regard, a priority-based execution and suspension model is introduced in SDL, which enables task-specific priority assignments in the SDL specification that are orthogonal to the static structure of SDL systems and control transition execution orders on design as well as on implementation level. Both the formal incorporation of real-time tasks into SDL and their implementation in a novel scheduling strategy are discussed in this context. By means of evaluations on wireless sensor nodes, evidence is provided that these extensions reduce worst-case execution times substantially, and improve the predictability of SDL implementations and the language's applicability to real-time systems

Model-driven and Compositional Service Creation in the Internet of Services

Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 2012In the Future Internet, billions of devices will be connected to the Internet. Devices at any levels of hierarchy provide software functionality that can be used by others. We can call the device’s functionality a service, which in turn, introduces the concept of the Internet of Services. From the software developer perspectives, a new service can be created by utilizing services in the Internet of Services. An important issue of the creation of such service-based application is regarding their deployment method on personalized and embedded devices. For each device with different capability and configuration, different tailored code is required. For this, a flexible method and tools that support an automatic code generation for a device with a specific capability and configuration are mandatory. This thesis proposes PMG-pro (Present, Model, Generate and provide), a language- independent, bottom-up and model-driven method for the service creation in the Internet of Services. With this method, a service is created by providing the new functionality of a service-based application as a service. By using existing service frameworks and APIs, from a service description, PMG-pro generates an abstract graphical service representation (service model) and source code implementing for service invocations. Depending on the target modeling languages, different graphical notations can be used to represent services. Similarly, different programming languages can also be used to implement the service invocations. We call these pairs (i.e., the service model and the source code) platform-specific models. With these platform models, service composers use the graphical service representation to model new service-based applications, while the machine (i.e., computer system) uses the source code to generate code from the service-based application model. This thesis contributes to the service engineering method that applies a modeldriven development approach. Three main contributions are a model-driven method for service creation, an automatic service presentation of pre-made services, and a new method of handling device capability and configuration. With these, service creation in the Internet of Services can be done in a rapid and automatic manner. Service designers can create a new service by defining a model of service-based applications using pre-made service models, while code for a specific device can be generated automatically from the model. The PMG-pro method has been partly prototyped and validated on various case studies in the domain of smart homes that have produced encouraging results. The method promotes a rapid, language-independent, and unified process of software service development

Model-driven and Compositional Service Creation in the Internet of Services

Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 2012In the Future Internet, billions of devices will be connected to the Internet. Devices at any levels of hierarchy provide software functionality that can be used by others. We can call the device’s functionality a service, which in turn, introduces the concept of the Internet of Services. From the software developer perspectives, a new service can be created by utilizing services in the Internet of Services. An important issue of the creation of such service-based application is regarding their deployment method on personalized and embedded devices. For each device with different capability and configuration, different tailored code is required. For this, a flexible method and tools that support an automatic code generation for a device with a specific capability and configuration are mandatory. This thesis proposes PMG-pro (Present, Model, Generate and provide), a language- independent, bottom-up and model-driven method for the service creation in the Internet of Services. With this method, a service is created by providing the new functionality of a service-based application as a service. By using existing service frameworks and APIs, from a service description, PMG-pro generates an abstract graphical service representation (service model) and source code implementing for service invocations. Depending on the target modeling languages, different graphical notations can be used to represent services. Similarly, different programming languages can also be used to implement the service invocations. We call these pairs (i.e., the service model and the source code) platform-specific models. With these platform models, service composers use the graphical service representation to model new service-based applications, while the machine (i.e., computer system) uses the source code to generate code from the service-based application model. This thesis contributes to the service engineering method that applies a modeldriven development approach. Three main contributions are a model-driven method for service creation, an automatic service presentation of pre-made services, and a new method of handling device capability and configuration. With these, service creation in the Internet of Services can be done in a rapid and automatic manner. Service designers can create a new service by defining a model of service-based applications using pre-made service models, while code for a specific device can be generated automatically from the model. The PMG-pro method has been partly prototyped and validated on various case studies in the domain of smart homes that have produced encouraging results. The method promotes a rapid, language-independent, and unified process of software service development

Multi-Agent Systems

This Special Issue ""Multi-Agent Systems"" gathers original research articles reporting results on the steadily growing area of agent-oriented computing and multi-agent systems technologies. After more than 20 years of academic research on multi-agent systems (MASs), in fact, agent-oriented models and technologies have been promoted as the most suitable candidates for the design and development of distributed and intelligent applications in complex and dynamic environments. With respect to both their quality and range, the papers in this Special Issue already represent a meaningful sample of the most recent advancements in the field of agent-oriented models and technologies. In particular, the 17 contributions cover agent-based modeling and simulation, situated multi-agent systems, socio-technical multi-agent systems, and semantic technologies applied to multi-agent systems. In fact, it is surprising to witness how such a limited portion of MAS research already highlights the most relevant usage of agent-based models and technologies, as well as their most appreciated characteristics. We are thus confident that the readers of Applied Sciences will be able to appreciate the growing role that MASs will play in the design and development of the next generation of complex intelligent systems. This Special Issue has been converted into a yearly series, for which a new call for papers is already available at the Applied Sciences journal’s website: https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems_2019

Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields

Innovations in Road, Railway and Airfield Bearing Capacity – Volume 2 comprises the second part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field

Modèles algorithmes et méthodologie pour la conception de systèmes de sécurité physique basés sur des microcontrôleurs protégés des attaques cyber-physiques

Un moyen d'assurer la sécurité de systèmes basés sur des micro-contrôleurs (mCS) est de considérer une approche de génération à partir de spécifications. Malheureusement, les approches existantes souffrent d'inconvénients, et le but de la méthodologie présentée dans cette thèse est de les éviter dans le cas particulier des mCS pour la sécurité physique (mCS-Sec). Les principaux résultats de ce travail sont le développement de modèles, d'algorithmes, et d'une méthodologie originale de création de mCS-Sec, et leur implémentation. L'applicabilité de la méthode a été évaluée sur un système de robot de surveillance d'une zone. Dans ce cas, notre évaluation a montré que l'approche développée satisfaisait toutes les contraintes imposées, tout en offrant certains avantages par rapport aux solutions existantes. Nous pensons que cette approche permettra de réduire le nombre de faiblesses et les problèmes d'architecture dans les mCS, ce qui en réduira la surface d'attaque.One of the possible ways to ensure the security of microcontroller-based systems is the implementation of security by design approach. Unfortunately, existing approaches are not without drawbacks, that is why this thesis is aimed at developing the new one. Moreover, among all possible systems, in this work, only physical security systems were chosen as an area of the application. The main findings of the work are containing original models, algorithms, methodology and software implementation. Their correctness was checked on a system of mobile robots for perimeter monitoring. The evaluation of the developed solution showed that it satisfies all requirements while having advantages over commercial and scientific analogues, which means that the goal of this work was reached. It is assumed that the use of the developed solution will help to reduce the number of weak places and architectural defects in microcontroller-based systems, thereby significantly reducing their attack surface