Combining personal trust Sample Clauses

Combining personal trust. The local trust introduced in Section 26.2.2 reflects a service consumer’s personal opinion of a service provider. To comprehensively analyse a service provider’s capability to enforce SLAs based on its historic performance, a service consumer’s local trust should be combined with other service consumer’s local trust when evaluating the service consumer’s global trust over the service provider. By doing so, the service consumer can obtain a global and comprehensive view of the service provider. A simple approach to the combination is to simply average all the local trust. An advanced approach is to compute a weighted average of all the local trust, where the weights represent the credibility of the local trust. The credibility of a service consumer’s local trust over a service provider depends not only on how old the local transactional ratings are (see Section 26.2.1), but also on how long the service consumer has had interactions with the service provider. Experience with the service provider in the longer-term gives the service consumer more information and knowledge about the service provider, thus enabling the service consumer to predict the service provider’s ability and behaviour better [29, 93]. It also provides a firmer basis for calculating the credibility of the service consumer’s local trust over the service provider. Therefore, when incorporating other service consumers’ local trust into evaluating a service consumer’s global trust over a service provider, we consider the relationship duration between the service consumers and the service provider, measured by the number of past service transactions between them. The longer relationship duration a service consumer has had with the service provider, the more credible its local trust over the service provider is. We adopt Rayleigh cumulative distribution functions [30] to calculate the weights according to the number of a service consumer’s past service transactions with the service provider. The credibility of service consumer i’s local trust over service provider j, denoted as βi,j , is calculated as follows: xx, x = 1 − exp( −x2 ) ( σ > 0 ) 2σ 2 (6.3) whereσ is a parameter that inversely controls how fast βi,j increases as the number of interactions, denoted as x, increases.σ can be set by the application developers, from 0 to theoretically∞ , to capture the characteristics of different application scenarios. Figure 6.3 presents an example of the calculation of βi,j using differentσ . Compare...