{"content":[{"text":"Software Test Techniques for \n System Fault-Tree Analysis","bbox":{"left":0.338358,"top":0.143413,"width":0.323344,"height":0.05442499999999997}},{"text":"John C. Knight & Luís G. Nakano \n Department of Computer Science, University of Virginia \n Charlottesville, VA 22903-2442, USA","bbox":{"left":0.314436,"top":0.215011,"width":0.37114700000000006,"height":0.056306999999999996}},{"text":"Abstract \n System fault-tree analysis is a technique for modeling dependability that is in \n widespread use. For systems that include software, the integration of software \n data into fault trees has proved problematic. In this paper we discuss a number \n of techniques that can be used to make the assessment of software dependabil- \n ity by testing both more tractable and more suitable for use in system fault-tree \n analysis. Some of the techniques are illustrated using an experimental control \n system for a research nuclear reactor as an example.","bbox":{"left":0.268553,"top":0.298345,"width":0.463197,"height":0.12157199999999996}},{"text":"1 Introduction \n Computers are introduced into applications for the many advantages that they pro- \n vide. But these advantages do not come without a price. The price is the complexity \n that the computer system brings with it. In addition to providing several advantages, \n the increased complexity has the potential for decreasing the dependability of the \n overall system. This can be dangerous in safety-critical systems where incorrect com- \n puter operation can be catastrophic [14]. \n For safety-critical systems, it is essential that various aspects of the dependabil- \n ity of the complete system, e.g., probability of failure per unit time, either be assessed \n or predicted before deployment. Assessment is usually performed by observing the \n system operating in a test environment. Predictions are usually obtained from mathe- \n matical models. \n The treatment of software has been a source of difficulty in the development of \n predictive models of computer-based systems. Acceptable quantification of a sys- \n tem’s software components has proved elusive. In this paper we consider the problem \n of making system dependability predictions using system fault-tree models that \n include appropriate analysis of software. We focus in particular on how the results of \n software testing can be made a practical source of probabilistic data for fault-tree \n analysis. By employing a variety of techniques including restricting software’s func- \n tionality and a very rigid software architecture, we show how various limitations in \n previous models can be overcome, and useful dependability predictions of complex \n systems produced. We illustrate the concepts using a small research nuclear reactor as \n an example. \n The reactor system example is reviewed in the next section. Following that, the \n issues in fault-tree analysis and the issues surrounding software are discussed. In the","bbox":{"left":0.222081,"top":0.440799,"width":0.555939,"height":0.40748900000000005}}],"images_bbox":[],"images_bbox_not_text_overlap":[]}