Reactive Safety

The distinction between safety and liveness properties is a fundamental classification with immediate implications on the feasibility and complexity of various monitoring, model checking, and synthesis problems. In this paper, we revisit the notion of safety for reactive systems, i.e., for systems whose behavior is characterized by the interplay of uncontrolled environment inputs and controlled system outputs. We show that reactive safety is a strictly larger class of properties than standard safety. We provide algorithms for checking if a property, given as a temporal formula or as a word or tree automaton, is a reactive safety property and for translating such properties into safety automata. Based on this construction, the standard verification and synthesis algorithms for safety properties immediately extend to the larger class of reactive safety.Comment: In Proceedings GandALF 2011, arXiv:1106.081

Learning-Based Synthesis of Safety Controllers

We propose a machine learning framework to synthesize reactive controllers for systems whose interactions with their adversarial environment are modeled by infinite-duration, two-player games over (potentially) infinite graphs. Our framework targets safety games with infinitely many vertices, but it is also applicable to safety games over finite graphs whose size is too prohibitive for conventional synthesis techniques. The learning takes place in a feedback loop between a teacher component, which can reason symbolically about the safety game, and a learning algorithm, which successively learns an overapproximation of the winning region from various kinds of examples provided by the teacher. We develop a novel decision tree learning algorithm for this setting and show that our algorithm is guaranteed to converge to a reactive safety controller if a suitable overapproximation of the winning region can be expressed as a decision tree. Finally, we empirically compare the performance of a prototype implementation to existing approaches, which are based on constraint solving and automata learning, respectively

Correct-by-synthesis reinforcement learning with temporal logic constraints

We consider a problem on the synthesis of reactive controllers that optimize some a priori unknown performance criterion while interacting with an uncontrolled environment such that the system satisfies a given temporal logic specification. We decouple the problem into two subproblems. First, we extract a (maximally) permissive strategy for the system, which encodes multiple (possibly all) ways in which the system can react to the adversarial environment and satisfy the specifications. Then, we quantify the a priori unknown performance criterion as a (still unknown) reward function and compute an optimal strategy for the system within the operating envelope allowed by the permissive strategy by using the so-called maximin-Q learning algorithm. We establish both correctness (with respect to the temporal logic specifications) and optimality (with respect to the a priori unknown performance criterion) of this two-step technique for a fragment of temporal logic specifications. For specifications beyond this fragment, correctness can still be preserved, but the learned strategy may be sub-optimal. We present an algorithm to the overall problem, and demonstrate its use and computational requirements on a set of robot motion planning examples.Comment: 8 pages, 3 figures, 2 tables, submitted to IROS 201

Reporting Error in Aircraft Maintenance: are engineers reporting safety concerns? : A thesis presented in partial fulfilment of the requirements for the degree of Master of Aviation At Massey University, Manawatu, New Zealand

Aviation accidents seldom occur as the consequence of an isolated incident, but as the result of a series of contributing factors. The industry has focussed on detecting and predicting these casual factors to support accident prevention. However, the complexity of aircraft maintenance errors makes them somewhat harder to capture. One method adopted to support error identification is error-reporting systems. The primary aim of study was to identify if reporting systems were being utilised by maintenance personnel. The secondary aim was to distinguish the factors that contribute to maintenance personnel rejecting reporting systems as a supportive tool. This was achieved through an online questionnaire. Due to a lack of research on error reporting and usability of reporting systems by aircraft maintenance personnel it proved difficult to use an existing survey, so survey questions were developed from an extensive literature review and a focus group made up of front-line personnel. Survey questions focussed on reporting system design, company attitude, error recognition and finally maintenance personnel personality patterns. Results showed several issues affected reporting system usage including lack of company support, inadequate training, and lack of feedback. Perhaps the most significant discovery were engineers believing that they would report error, but were inadequately able to recognise error. Although regulatory authorities and organisations themselves are seeing the benefits of a positive reporting culture the current study showed there are still significant issues with current reporting systems, without these inhibiting factors being addressed the industry cannot solely rely on self-reporting to manage error

Safety Culture ≈ Multi - Dimensional Phenomenon

Článok poukazuje na rozdielnosť vnímania pojmu kultúra bezpečnosti v odbornej sfére ako aj na nejednotu defi nícií pojmu. Prezentuje možné modely fungovania kultúry bezpečnosti a základné otázky, ktoré je nutné zodpovedať. Ďalej poukazuje na nevyhnutnosť zapojenia managementu fi rmy pre dobré fungovanie systému, ako aj na ďalšie faktory, ktoré fi remnú kultúru bezpečnosti ovplyvňujú.The paper refers to the difference of perception of the concept of safety culture in the professional sphere as well as the defi nitions of disunity. It presents possible models of functioning safety culture and the fundamental questions that must be answered. Furthermore, it highlights the need for the involvement of the company management for the proper functioning of the system as well as other factors that infl uence the corporate culture of safety

Tracking Report 2011 Fifth & Pacific, India 980232266J

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.FLA_2011_Fifth_Pacific_TR_India_980232266J.pdf: 15 downloads, before Oct. 1, 2020

Tracking Chart 2011 American Eagle Outfitters, India 980232266J

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.FLA_2011_AmericanEagleOutfitters_TR_India_980232266J.pdf: 33 downloads, before Oct. 1, 2020

Development of a Safety Performance Decision-Making Tool for Flight Training Organizations

The purpose of the research was to create and validate a safety performance decision-making tool to transform a reactive safety model into a predictive, decision-making tool, specific to flight training organizations, to increase safety and aid in operational decision-making. Using Monte Carlo simulation, the study conducted simulation runs based on operational ranges to simulate the operating conditions with varying levels of controllable resources in terms of personnel (Aviation Maintenance Technicians and Instructor Pilots) and expenditures (active flight students and available aircraft). Four What-if Scenarios were conducted by manipulating the controllable inputs. Changes to the controllable inputs are reflected by variations to the outputs demonstrating the utility and potential for the safety performance decision-making tool. The outputs could be utilized by safety personnel and administrators to make more informed safety-related decisions without expending unnecessary resources

An Analysis of the Role of Safety Nets in the National Airspace System

Safe operations of aircraft in the National Airspace System (NAS) may be attributed to many factors, including the application of a variety of safety nets (SNs) as a last line of defense. In preparation for the Next Generation Air Transportation System (NextGen), a review of Aviation Safety Reporting System (ASRS) reports for incidents with positive outcomes was conducted to investigate the importance of current safety nets. The examination of positive outcomes not only shows what went wrong, but also what went right to prevent accidents and save the day. More than 400 incident reports for 2015 from the voluntary ASRS reporting database were studied in detail to create event sequence diagrams (ESDs), illustrating the effectiveness of SNs. The developed ESDs are considered top-level, representative models and are limited with respect to being reliably quantitative because they are based on only reports from a single year. The ESDs could offer insights into human systems integration research, such as strategically using technologies as SNs without human interface or alleviating human workload with new technologies to provide resilient recovery from off-nominal conditions ensuring flight safety