System Level Synthesis

This article surveys the System Level Synthesis framework, which presents a novel perspective on constrained robust and optimal controller synthesis for linear systems. We show how SLS shifts the controller synthesis task from the design of a controller to the design of the entire closed loop system, and highlight the benefits of this approach in terms of scalability and transparency. We emphasize two particular applications of SLS, namely large-scale distributed optimal control and robust control. In the case of distributed control, we show how SLS allows for localized controllers to be computed, extending robust and optimal control methods to large-scale systems under practical and realistic assumptions. In the case of robust control, we show how SLS allows for novel design methodologies that, for the first time, quantify the degradation in performance of a robust controller due to model uncertainty -- such transparency is key in allowing robust control methods to interact, in a principled way, with modern techniques from machine learning and statistical inference. Throughout, we emphasize practical and efficient computational solutions, and demonstrate our methods on easy to understand case studies.Comment: To appear in Annual Reviews in Contro

Towards improved performance and interoperability in distributed and physical union catalogues

Purpose of this paper: This paper details research undertaken to determine the key differences in the performance of certain centralised (physical) and distributed (virtual) bibliographic catalogue services, and to suggest strategies for improving interoperability and performance in, and between, physical and virtual models. Design/methodology/approach: Methodically defined searches of a centralised catalogue service and selected distributed catalogues were conducted using the Z39.50 information retrieval protocol, allowing search types to be semantically defined. The methodology also entailed the use of two workshops comprising systems librarians and cataloguers to inform suggested strategies for improving performance and interoperability within both environments. Findings: Technical interoperability was permitted easily between centralised and distributed models, however the various individual configurations permitted only limited semantic interoperability. Significant prescription in cataloguing and indexing guidelines, greater participation in the Program for Collaborative Cataloging (PCC), consideration of future 'FRBR' migration, and greater disclosure to end users are some of the suggested strategies to improve performance and semantic interoperability. Practical implications: This paper informs the LIS research community and union catalogue administrators, but also has numerous practical implications for those establishing distributed systems based on Z39.50 and SRW, as well as those establishing centralised systems. What is original/value of the paper?: The paper moves the discussion of Z39.50 based systems away from anecdotal evidence and provides recommendations based on testing and is intimately informed by the UK cataloguing and systems librarian community

Proposing a secure component-based-application logic and system’s integration testing approach

Software engineering moved from traditional methods of software enterprise applications to com-ponent based development for distributed system’s applications. This new era has grown up forlast few years, with component-based methods, for design and rapid development of systems, butfact is that , deployment of all secure software features of technology into practical e-commercedistributed systems are higher rated target for intruders. Although most of research has been con-ducted on web application services that use a large share of the present software, but on the otherside Component Based Software in the middle tier ,which rapidly develops application logic, alsoopen security breaching opportunities .This research paper focus on a burning issue for researchersand scientists ,a weakest link in component based distributed system, logical attacks, that cannotbe detected with any intrusion detection system within the middle tier e-commerce distributed ap-plications. We proposed An Approach of Secure Designing application logic for distributed system,while dealing with logically vulnerability issue

Towards realization of an Energy Internet: Designing distributed energy systems using game-theoretic approach

Distributed energy systems play a significant role in the integration of renewable energy technologies. The Energy Internet links a fleet of distributed energy systems to each other and with the grid. Interactions between the distributed energy systems via information sharing could significantly enhance the efficiency of their real-time operation. However, privacy and security concerns hinder such interactions. A game-theoretic approach can help in this regard, and enable consideration of some of these factors when maintaining interactions between energy systems. Although a game-theoretic approach is used to understand energy systems\u27 operation, such complex interactions between the energy systems are not considered at the early design phase, leading to many practical problems, and often leading to suboptimal designs. The present study introduces a game-theoretic approach that enables consideration of complex interactions among energy systems at the early design phase. Three different architectures are considered in the study, i.e., energy eystem prior to grid (ESPG), fully cooperative (FCS), and non-cooperative (NCS) scenarios, in which each distributed energy system is taken as an agent. A novel distributed optimization algorithm is developed for both FCS and NCS. The study reveals that FCS and NCS reduce the cost, respectively, by 30% and 15% compared to ESPG. In addition to cost reduction, there is a significant change in the energy system design when moving from FCS to NCS scenarios, clearly indicating the requirement for a scenario that lies between NCS and FCS. This will lead to reducing design costs while maintaining privacy

A Web-Based Distributed Virtual Educational Laboratory

Evolution and cost of measurement equipment, continuous training, and distance learning make it difficult to provide a complete set of updated workbenches to every student. For a preliminary familiarization and experimentation with instrumentation and measurement procedures, the use of virtual equipment is often considered more than sufficient from the didactic point of view, while the hands-on approach with real instrumentation and measurement systems still remains necessary to complete and refine the student's practical expertise. Creation and distribution of workbenches in networked computer laboratories therefore becomes attractive and convenient. This paper describes specification and design of a geographically distributed system based on commercially standard components

Codifying distributed cognition: a case study of emergency medical dispatch

The theory of distributed cognition is recognised as being relevant to system analysis and design but it has lacked visibility for practice. In this paper I develop a codified method of analysis based on distributed cognition which provides both structure and guidance in the use of the theory. The method developed comprises a systematic exploration and description of three functional levels of a system, namely, the information flow model, physical model, and artefact model. These levels are analytically separate but integrate in modelling the propagation and transformation of information within a system. The approach to developing this method has been exploratory and iterative: developing the understanding of distributed cognition and contextual study literature, with practical application to the London Ambulance Service Central Ambulance Control room context. The application of the method to this context reveals a number of design issues and concerns lending support to its use in these situations. Furthermore, this paper introduces a conception of how distributed cognition can be used to deliberate about potential design scenarios, which is a use of distributed cognition that has been alluded to but has not been explained elsewhere. This paper makes progress in narrowing the gap between distributed cognition theory and practice by adding guidance through a structured codified methodology. The method provides an accessible, practical approach to analysing team based systems using distributed cognition