An important problem in trust management area is to evaluate the trust value among two nodes in a web of trust using intermediate nodes. This is widely used when the source node has no experience of direct interaction with the target. If trust is used to support decision making, it is important to have not only an accurate estimate of trust, but also a measure of confidence in the intermediate nodes and in the final estimated value of trust. In this paper we introduce a novel approach for representation of trust and confidence -both together- using intervals. Based on this representation, we then propose a kind of summation operation that is a method for calculating the resultant of trust opinions. We show that this operator is more accurate for evaluation of trust resultant than the usual method of weighted­ averaging. We also report and analyze the results of experiments carried out on a well-known trust dataset which show that our proposed method reduces the average absolute difference and increases the correlation among the inferred and direct values of trust comparing to the weighted-averaging method.

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