Expert Assessment of Arguments: A Method and Its Experimental Evaluation

Argument structures are commonly used to develop and present cases for safety, security and other properties. Such argument structures tend to grow excessively. To deal with this problem, appropriate methods of their assessment are required. Two objectives are of particular interest: (1) systematic and explicit assessment of the compelling power of an argument, and (2) communication of the result of such an assessment to relevant recipients. The paper gives details of a new method which deals with both problems. We explain how to issue assessments and how they can be aggregated depending on the types of inference used in arguments. The method is fully implemented in a software tool. Its application is illustrated by examples. The paper also includes the results of experiments carried out to validate and calibrate the method.