Automatic Generation of Hierarchical Contracts for Resilience in Cyber-Physical Systems

With the growing scale of Cyber-Physical Systems (CPSs), it is challenging to maintain their stability under all operating conditions. How to reduce the downtime and locate the failures becomes a core issue in system design. In this paper, we employ a hierarchical contract-based resilience framework to guarantee the stability of CPS. In this framework, we use Assume Guarantee (A-G) contracts to monitor the non-functional properties of individual components (e.g., power and latency), and hierarchically compose such contracts to deduce information about faults at the system level. The hierarchical contracts enable rapid fault detection in large-scale CPS. However, due to the vast number of components in CPS, manually designing numerous contracts and the hierarchy becomes challenging. To address this issue, we propose a technique to automatically decompose a root contract into multiple lower-level contracts depending on I/O dependencies between components. We then formulate a multi-objective optimization problem to search the optimal parameters of each lower-level contract. This enables automatic contract refinement taking into consideration the communication overhead between components. Finally, we use a case study from the manufacturing domain to experimentally demonstrate the benefits of the proposed framework.Comment: \copyright 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work

Demo Abstract: Contract-based Hierarchical Resilience Framework for Cyber-Physical Systems

This demonstration presents a framework for building a resilient Cyber-Physical Systems (CPS) cyber-infrastructure through the use of hierarchical parametric assume-guarantee contracts. A Fischertechnik Sorting Line with Color Detection training model is used to showcase our framework.Comment: 2 pages, 5 figures, published in the Demo Session of IEEE International Conference on Cyber-Physical Systems 2019. Publication rights licensed to AC

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Achieving resilience for cyber-physical systems with 4DIAC IEC 61499 through parametric contracts

Industry 4.0 has garnered much interest in traditional manufacturing setups to play catch up with the state-of-the-art. This fourth industrial revolution has caused a proliferation of computing devices and sensors onto the factory floor. This proliferation has also caused a paradigm shift in the designing of the plant supervisory management control systems such as Supervisory Control and Data Acquisition, which traditionally controls the automation systems for manufacturing plants and manages the fault recovery mechanisms. With this said, the fourth industrial revolution requires a new framework to improve resiliency in these systems to account for a large number of interconnected devices in a Cyber-Physical System (CPS). Software-based resilience solutions can provide the necessary flexibility in dealing with failures to reduce downtime and the need for human intervention. We present a contract-based resilience framework for CPS that incorporates Assume-Guarantee contracts to define the user requirements of the CPS. These contracts describe the non-functional requirements which the system is expected to meet and provides a threshold for triggering an alarm (i.e., a fault occurrence). The top-level contract (i.e., root contract) represents the overall requirement of the system, and this necessitates decomposition, which is the process of decomposing the root contract into smaller sub-contracts. The decomposed sub-contracts represent the requirements asked of the different interconnected components in the system. The framework also has observers which serve to check for violations of the sub-contracts and Resilience Managers (RMs) who manage the set of sub-contracts. Together, RMs and observers form a logical hierarchy for decentralized fault monitoring of the entire CPS. A Fischertechnik Sorting Line with Color Detection training model, which represents a factory's assembly line, as well as an industrial Festo Didactic Cyber-Physical Factory, are used to demonstrate the capabilities of the resilience framework. Both the control logic and resilience framework of the assembly line use an open-source platform, 4DIAC, which is a Programmable Logic Controller framework for distributed industrial control based on the International Electrotechnical Commission 61499 standard. The process described above would require a great deal of manual work if it were to be done for a large-scale CPS. As part of our contribution, we present an automated way of generating the contract hierarchy and deploying it on 4DIAC. This process starts from defining the user requirements, which is in the form of a root contract, and the hardware information of the CPS in an AutomationML (AML) file. Then, the information from the AML file is used to decompose the root contract into a hierarchy of sub-contracts. The entire process completes when we port the decomposed contracts onto the 4DIAC platform by generating the function blocks for resilience management (i.e., RM and observer blocks). The user can then download the function blocks onto its associated hardware for deployment. Finally, we demonstrate the framework on an industrial testbed to showcase the framework with better interoperability. This master's report presents the translation of a resilience framework into reality.Master of Engineerin

Profiling a multi-core (Freescale P4080)

Multi-cores can be seen in almost every device out there in the world today. Yet, this processor architecture has yet seen its widespread implementation in safety-critical systems such as the automotive and aerospace industries. Many researchers have tried to theoretically show that multi-cores demonstrate unpredictability in their execution through analysis of the multi-core architecture. This project aims to be able to substantiate such claims that shared resources which include shared cache, memory interconnects and main memory would create contention in these resources and result in un-deterministic execution times. We will be exploring the use of a hypervisor to securely and robustly partition a multi-core system and try to emulate Asymmetric Multiprocessing (AMP) implementations. Our findings show that multi-cores may yet be adequate to support safety-critical applications to meet their real time constraints.Bachelor of Engineering (Computer Engineering

Contract-based Methodology for Developing Resilient Cyber-Infrastructure in the Industry 4.0 Era

As the industrial cyber-infrastructure become increasingly important to realise the objectives of Industry 4.0, the consequence of disruption due to internal or external faults become increasingly severe. Thus there is a need for a resilient infrastructure. In this paper, we propose a contractbased methodology where components across layers of the cyberinfrastructure are associated with contracts and a light-weight resilience manager. This allows the system to detect faults (contract violation monitored using observers) and react (change contracts dynamically) effectively.NRF (Natl Research Foundation, S’pore)Accepted versio

Contract-based hierarchical resilience management for cyber-physical systems

Cyber-physical systems satisfy user requirements through close collaboration among physical and cyber components. Software-based resilience management solutions can provide flexibility in dealing with component failures. To improve efficiency and ease of implementation, we present a contract-based hierarchical resilience management framework.National Research Foundation (NRF)Accepted versionWe acknowledge the contributions from Sidharta Andalam, Delta Electronics Singapore, for input on related works and formalization of contracts. This work was conducted within the Delta-NTU Corporate Lab for Cyber-Physical Systems with funding support from Delta Electronics Inc. and the National Research Foundation Singapore under the Corp Lab @ University Scheme