Best matching processes in distributed systems

The growing complexity and dynamic behavior of modern manufacturing and service industries along with competitive and globalized markets have gradually transformed traditional centralized systems into distributed networks of e- (electronic) Systems. Emerging examples include e-Factories, virtual enterprises, smart farms, automated warehouses, and intelligent transportation systems. These (and similar) distributed systems, regardless of context and application, have a property in common: They all involve certain types of interactions (collaborative, competitive, or both) among their distributed individuals—from clusters of passive sensors and machines to complex networks of computers, intelligent robots, humans, and enterprises. Having this common property, such systems may encounter common challenges in terms of suboptimal interactions and thus poor performance, caused by potential mismatch between individuals. For example, mismatched subassembly parts, vehicles—routes, suppliers—retailers, employees—departments, and products—automated guided vehicles—storage locations may lead to low-quality products, congested roads, unstable supply networks, conflicts, and low service level, respectively. This research refers to this problem as best matching, and investigates it as a major design principle of CCT, the Collaborative Control Theory. The original contribution of this research is to elaborate on the fundamentals of best matching in distributed and collaborative systems, by providing general frameworks for (1) Systematic analysis, inclusive taxonomy, analogical and structural comparison between different matching processes; (2) Specification and formulation of problems, and development of algorithms and protocols for best matching; (3) Validation of the models, algorithms, and protocols through extensive numerical experiments and case studies. The first goal is addressed by investigating matching problems in distributed production, manufacturing, supply, and service systems based on a recently developed reference model, the PRISM Taxonomy of Best Matching. Following the second goal, the identified problems are then formulated as mixed-integer programs. Due to the computational complexity of matching problems, various optimization algorithms are developed for solving different problem instances, including modified genetic algorithms, tabu search, and neighbourhood search heuristics. The dynamic and collaborative/competitive behaviors of matching processes in distributed settings are also formulated and examined through various collaboration, best matching, and task administration protocols. In line with the third goal, four case studies are conducted on various manufacturing, supply, and service systems to highlight the impact of best matching on their operational performance, including service level, utilization, stability, and cost-effectiveness, and validate the computational merits of the developed solution methodologies

Speculative Concurrency Control for Real-Time Databases

In this paper, we propose a new class of Concurrency Control Algorithms that is especially suited for real-time database applications. Our approach relies on the use of (potentially) redundant computations to ensure that serializable schedules are found and executed as early as possible, thus, increasing the chances of a timely commitment of transactions with strict timing constraints. Due to its nature, we term our concurrency control algorithms Speculative. The aforementioned description encompasses many algorithms that we call collectively Speculative Concurrency Control (SCC) algorithms. SCC algorithms combine the advantages of both Pessimistic and Optimistic Concurrency Control (PCC and OCC) algorithms, while avoiding their disadvantages. On the one hand, SCC resembles PCC in that conflicts are detected as early as possible, thus making alternative schedules available in a timely fashion in case they are needed. On the other hand, SCC resembles OCC in that it allows conflicting transactions to proceed concurrently, thus avoiding unnecessary delays that may jeopardize their timely commitment

Formal analysis techniques for gossiping protocols

We give a survey of formal verification techniques that can be used to corroborate existing experimental results for gossiping protocols in a rigorous manner. We present properties of interest for gossiping protocols and discuss how various formal evaluation techniques can be employed to predict them

Performances de protocoles transactionnels en environnement mobile

National audience. L'omniprésence d'unités mobiles et le développement des réseaux sans fil motivent des avancées en matière de supports d'exécution pour une grande variété d'applications en envi-ronnement mobile. Des efforts importants sont faits pour offrir une bonne gestion des données malgré les caractéristiques limitées de tels environnements. La notion de transaction a été ré-étudiée pour proposer des modèles et des protocoles permettant d'assurer certaines propriétés transactionnelles. Les algorithmes et protocoles proposés tentent d'optimiser l'utilisation des ressources des unités mobiles et de surmonter les limitations du réseau mobile. Dans cet article nous nous intéressons spécifiquement aux protocoles de validation de transactions réparties sur plusieurs unités dont certaines mobiles. Nous présentons ici les résultats d'un travail qui iden-tifie des propriétés qualitatives et des indices de performance quantitatifs, et étudie ceux-ci sur quatre protocoles (2PC, UCM, CO2PC et TCOT). Trois de ces protocoles sont des propositions spécifiques pour des environnements mobiles et sont représentatifs des propositions actuelles. Nous nous intéressons à la phase de validation des transactions, ainsi qu'à l'influence des dif-férents protocoles sur les performances du déroulement de l'ensemble des transactions. ABSTRACT. This is an abstract. The omnipresence of mobile devices and wireless networks lead to a growing interest in supporting a wide variety of applications in mobile environments. Numerous efforts in providing appropriate data managements for such environments are made. Transaction supports have been revisited to propose adapted transaction models and properties. Proposed algorithms and protocols try to optimise the use of mobile units resources and to overcome wireless network limitations. This work concerns protocols to commit transactions distributed over several mobile and fixed units. Results presented here concern the identification of qualitative properties and quantitative performance indices that are studied on four protocols (2PC, UCM, CO2PC et TCOT). Three of them are specifics propositions for mobile environments and are representative of current proposals. The analysis concerns the transaction validation phase as well as the impact of the protocols on the performances during a transaction execution itself. MOTS-CLÉS : transactions mobiles , evaluation de performances, protocoles de validation

TURTLE-P: a UML profile for the formal validation of critical and distributed systems

The timed UML and RT-LOTOS environment, or TURTLE for short, extends UML class and activity diagrams with composition and temporal operators. TURTLE is a real-time UML profile with a formal semantics expressed in RT-LOTOS. Further, it is supported by a formal validation toolkit. This paper introduces TURTLE-P, an extended profile no longer restricted to the abstract modeling of distributed systems. Indeed, TURTLE-P addresses the concrete descriptions of communication architectures, including quality of service parameters (delay, jitter, etc.). This new profile enables co-design of hardware and software components with extended UML component and deployment diagrams. Properties of these diagrams can be evaluated and/or validated thanks to the formal semantics given in RT-LOTOS. The application of TURTLE-P is illustrated with a telecommunication satellite system