Elisabeth A. Strunk

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The computer systems that provide the information underpinnings for critical infrastructure applications, both military and civilian, are essential to the operation of those applications. Failure of the information systems can cause a major loss of service, and so their dependability is a major concern. Current facets of dependability, such as reliability(More)
Assurance based development (ABD) is the synergistic construction of a critical computing system and an assurance case that sets out the dependability claims for the system and argues that the available evidence justifies those claims. Co-developing the system and its assurance case helps software developers to make technology choices that address the(More)
The failure of a safety-critical system, though undesirable, is often a source of valuable lessons that can help prevent future failures. Current analysis practices do not always yield as much knowledge as they might about possible flaws in the system safety argument. In this paper, we introduce the lifecycle for safety cases. We use it to develop a(More)
Software-intensive systems often exhibit dimensions in size and complexity that exceed the scope of comprehension of system designers and analysts. With this complexity comes the potential for undetected errors in the system. While software often causes or exacerbates this problem, its form can be exploited to ameliorate the difficulty in what is referred(More)
Problem frames and assurance cases are two current research areas that can improve - and have improved - system dependability, in critical and noncritical systems alike. While these two techniques are effective separately, their synthesis is much more powerful. This paper describes the rationale behind the synthesis, the particular pieces that influence(More)
Predictably achieving requirements validity has proven extremely difficult because of the informal nature of this property, and poor communication of application domain knowledge is implicated as a main barrier to increasing this validity. In related work, we developed a methodology that exploits cognitive psychology research to improve this communication.(More)
In many software systems, properties necessary for dependable operation are only a small subset of all desirable system properties. Assuring properties over the simpler subset can provide assurance of critical properties over the entire system. This work provides a method for constructing systems to be dependably reconfigurable. A system's primary function(More)
Hardware dependability improvements have led to a situation in which it is sometimes unnecessary to employ extensive hardware replication to mask hardware faults. Expanding upon our previous work on assured reconfiguration for single processes and building upon the fail-stop model of processor behavior, we define a framework that provides assured(More)