Abstract
The paper proposes a procedure for the integrated application of methods for scenario analysis and prediction, represented by graphs of the «tree» type. The task on analysis of risks in software projects has been considered, the cause of which are the possible programming errors that lead to failures in the operation of systems and software. The joint use of a failure tree and a probability tree makes it possible to generate the sequences of scripts for the implementation of an adverse event, whose main cause is possible defects or errors in software or data, as well as to assess the probabilities of their realization. Such an approach allows the identification of the overall result of the influence of certain risk-forming factors (defects) on the development of possible negative consequences (failures and malfunctions) or damage to the operation of complex software systems. This makes it possible to timely identify and propose effective mechanisms to manage software risk in order to reduce and eliminate them.A procedure has been proposed for aggregating individual probabilistic expert assessments of the occurrence of a risk event. Such an approach makes it possible to obtain group expert estimates assessing the feasibility of a risk event based on the constructed system of random events into a generalized expert assessment. The probabilities of the occurrence of a risk event, thus obtained, are used when constructing a probability tree and calculating the ratios of probabilistic inference using it. Aggregation of individual expert estimates is carried out by combining them based on a mathematical apparatus of the theory of evidence and the theory of plausible and paradoxical reasoning. It was established that in order to improve quality of the results of combining it is appropriate to establish an order for combining expert evidence and apply one of the rules of conflict redistribution as a combination rule.Numerical calculations of the proposed procedure for integrated application of a failure tree and a probability tree are provided. The results obtained make it possible to run a more in-depth analysis of the examined software systems and objects, and are aimed at improving the quality and effectiveness of managing risks in software projects caused by defects in programs and data
Highlights
The development of scenario prediction led to the deve lopment of two basic instrumental methods
We set the following tasks to achieve the objective: – to develop a procedure for aggregation of individual expert assessments of possibility of manifestation of a negative event in solution of probabilistic inference problems based on scenarios constructed using probability trees; – to investigate a possibility for an integrated application of a fault tree and a probability tree on the example of gene ration of sequence of scenarios of occurrence of risk events caused by failures of software and analysis of their consequences; – to run a computational experiment and analyze the results obtained
We have proposed in this study to use the combination mechanism based on one of the rules from the theory of evi dence or the theory of plausible and paradoxical reasoning for the aggregation of individual expert assessments of a possibility of the occurrence of a risk event
Summary
The development of scenario prediction led to the deve lopment of two basic instrumental methods. It does not make it possible to reflect a set of reasons that arise simultaneously and cause negative consequences (emergencies) The solution of this problem lies in the integrated application of existing methods and means of scenario prediction aimed at identification of causes of emergence of risk factors and prediction of possible scenarios of development of their consequences. In this context, the combined use of methods aimed at identification of causes of negative events and pro babilistic methods is expedient. It is possible to perform an analysis of such effects using a probability tree
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