37787829
The epistemics of accidents
Human intervention has played a critical role in the causes of many major accidents. At Three Mile Island, the operators isolated a reactor from its heat sink. The pilots of the Boeing 737 at Kegworth managed to shut down their one functioning engine. Staff continued to allow trains to deposit passengers in Kings? Cross after the fire had started. In retrospect, it seems impossible to predict all of the ways that human intervention might threaten safety. It is, therefore, important that we learn as much as possible from those accidents that do occur. This task is complicated because conventional accident reports contain many hundreds of pages of prose. They present findings drawn from many different disciplines: metallurgy; systems engineering; human factors; meterology. These findings are, typically, separated into a number of distinct chapters. Each section focuses upon a different aspect of the accident. This makes it difficult for designers to recognize the ways in which operator intervention and system failure combine during major failures. The following pages use formal methods to address these concerns. It is argued that mathematical specification techniques can represent human factors and system failures. Unfortunately, formal methods have not previously been used to analyse the factors that motivate operator intervention. This paper, therefore, argues that epistemic extensions of mathematical notations must be recruited in order to support the formal analysis of major accidents.
846602
Incident and Accident Investigation Techniques to Inform Model-Based Design of Safety-Critical Interactive Systems
The quality of the design of an interactive safety-critical system can be enhanced by embedding data and knowledge from past experiences. Traditionally, this involves applying scenarios, usability analysis, or the use of metrics for risk analysis. In this paper, we present an approach that uses the information from incident investigations to inform the development of safety-cases that can, in turn, be used to inform a formal system model, represented using Petri nets and the ICO formalism. The foundations of the approach are first detailed and then exemplified using a fatal mining accident case study.
18914756
The Impact of Time and Place on the Operation of Mobile Computing Devices
Recent improvements in the quality and reliability of wireless communications has led to the development of a range of mobile computing devices. Many portable computers now offer modem connections through cellular and satellite telephone networks. Taxi services, emergency vehicles, domestic repair teams all now rely upon mobile links to central computing systems. In spite of these advances, a number of technical problems still affect the quality of interaction with mobile applications. Electromagnetic interference blocks radio signals. Obstacles in the line of sight can interrupt microwave and infra-red transmissions. Tracking problems frustrate the use of low-level satellites. Transmission delays affect the service provided by higher, geostationary satellites. From the users’ point of view, these problems manifest themselves as geographical constraints upon the usability of their ‘mobile’ device. This lead to delays in the transmission of critical information. These, in turn, lead to the frustration and error that often complicates the operation of mobile computer systems. In the short term, it seems unlikely that the technical limitations will be resolved. The following pages, therefore, argue that interface designers must consider means of reducing the impact of geographic allocation upon the operation of mobile computing devices.
10158972
On the Problems of Validating DesktopVR
For the last twenty years, human-computer interfaces have been dominated by two-dimensional interaction techniques. Things are changing. Techniques that were previously restricted to specialized CAD/CAM tools and immersive VR systems are now being extended to the mass market. The photo-realistic facilities offered by QuicktimeVR and the model based renderings of VRML (Virtual Reality Mark-up Language) provide sophisticated tools for interface design. As a result, three dimensional visualization techniques are being widely exploited in the financial services industry, airports and even off-shore oil production. In January 1997, there were some 2,000 VRML models on the web. By January 1998, this number had grown to over 20,000. Research in human-computer interaction has, however, lagged behind these developments. Few guidelines can be applied to support the design of desktopVR. This paper, therefore, describes three criteria that can be applied to assess the usability of these interfaces. We then go on to validate these criteria against a number of case studies. Unfortunately, it is concluded that standard measures of task performance, successful navigation and subjective satisfaction cannot easily be applied to assess the utility of 3D systems.
15495731
The Team-Based Operation of Safety-Critical Programmable Systems in US Commercial Aviation and the UK Maritime Industries
This paper analyzes a range of incidents involving team-based interaction with safety-critical programmable systems. The incidents were submitted to NASA’s Aviation Safety Reporting System (ASRS) and to the UK Marine Accident Investigation Branch (MAIB) between December 2001 and February 2003. Our results show that incidents, which complicated the team-based operation of safety-critical, computer systems in commercial aviation, are now being reported within the UK maritime industry. This reflects the increasing use of programmable navigation and collision avoidance devices both in ferry operations and in commercial fishing. For example, many incidents in both industries now stem from operators making inappropriate assumptions about the likely behavior of co-workers and their programmable systems even though part of their task is to actively monitor those activities. Our results also show that a growing number of incidents are triggered when teams must rapidly reprogram complex, safety-critical systems in response to unpredictable changes in their operational requirements.
9129216
A formal and structured approach to the use of task analysis in accident modelling
Recent work (Telford & Johnson, 1996; Johnson, 1997), involving the application of formal notations to analyse accident reports has shown that the quality of these accident reports is poor, so much so that their conclusions can be misleading. The proposed solution has been to use formal notations in combination with traditional analysis to produce a report, the conclusions of which can be verified by formal reasoning. However, there are weaknesses with the formal notations used up until now. Firstly, they have not allowed the representation of all aspects of an accident or incident. For example, human factors have either not been represented or not clearly delineated from system factors. In particular, there has not been an attempt to provide a task analysis of the incident. Secondly, the notations used do not easily facilitate the system engineering concepts of modularity, encapsulation or scalability. In consequence, it is difficult to model different aspects of an accident, compose these different aspects to build up the model or make changes to parts of the model without affecting the rest of the model. The purpose of this paper is to demonstrate how a formal object-oriented specification language can be used to provide the benefits offered by an engineering approach and in particular, by using this approach, how a task analysis model can be constructed. The task analysis incorporates Hollnagel's (1993) classification of erroneous actions, so that scenarios, deriving from human error, can be reasoned about. An air accident investigation report, issued by the UK Civil Aviation Authority, is used as a case study.
18085576
Semantic errors - diagnosis and repair
In compiler technology, semantic error handling has too often used ad hoc techniques and terse messages of fixed content. In contrast, we present general models of diagnosis and repair of semantic errors and illustrate their use in the York Ada Workbench Compiler. The diagnostic model focuses upon the problem of selecting suitable information from which the programmer can locate and correct an error; following a brief discussion of an approach in which <underline>filters</underline> are applied to reports, and we give a more extensive account of a new approach using an <underline>interactive diagnostic interpreter</underline>. The repair model is based upon the idea of <underline>plastic</underline> nodes which are introduced into the compiler's internal representation of a program to replace <underline>normal</underline> nodes which are missing or erroneous.
35998651
Artificial Immune System Programming for Symbolic Regression
Artificial Immune Systems are computational algorithms which take their inspiration from the way in which natural immune systems learn to respond to attacks on an organism. This paper discusses how such a system can be used as an alternative to genetic algorithms as a way of exploring program-space in a system similar to genetic programming. Some experimental results are given for a symbolic regression problem. The paper ends with a discussion of future directions for the use of artificial immune systems in program induction.
17884377
Converse to the Parter-Wiener theorem: The case of non-trees
Through a succession of results, it is known that if the graph of an Hermitian matrix A is a tree and if for some index j, @l@?@s(A)@?@s(A(j)), then there is an index i such that the multiplicity of @l in @s(A(i)) is one more than that in A. We exhibit a converse to this result by showing that it is generally true only for trees. In particular, it is shown that the minimum rank of a positive semidefinite matrix with a given graph G is =
21779382
Computational Engineering and Science Program at the University of Utah
We describe a new graduate program at the Univesity of Utah that we consider a first step towards the modernization of the University's curriculum in what we call "Computational Engineering and Science" (CES). Our goal is to provide a mechanism by which a graduate student can obtain integrated expertise and skills in all areas that are required for the solution of a particular computational problem.
7042682
Choosing people: the role of social capital in information seeking behaviour
It is an almost universal finding in studies investigating human information behaviour that people choose other people as their preferred source of information. An explanation for the use of people as information sources is that they are easier to approach than more formal sources and therefore are a least effort option. However there have been few studies that have investigated who the people chosen as information sources are and what their relationship to the information seeker is. This paper reports findings that come out of a larger investigation of the information seeking behaviour of a random sample of residents of Ulaanbaatar, Mongolia. Using the theory of social capital as a conceptual framework and the methods of social network analysis, this study investigated the relational factors associated with the choice of people as information sources. Results indicate that respondents chose people who had better resources than they had and were not well known by them. This suggests that respondents were deliberate in their choice of people information sources and therefore it is speculated that people are not necessarily the least effort option but may require considerable effort to seek out and consult.