# Toward a Trust Evaluation Mechanism in the Social Internet of Things
## 2 Augmentation of Trust Concept in the SIoT
### Trustworthiness and Trustworthiness Attributes  
According to the proposed conceptual trust model, in order to quantify trust, it is necessary to investigate trustee's trustworthiness by specifying TAs associated with it. As mentioned above, trustworthiness is as a composite of a variety of TAs that illustrate different characteristics of the trustee. Despite a large number of TAs have been figured out in trust-related literature, TAs are mostly fallen into three categories as the three main dimensions of trustworthiness: Ability, Benevolence and Integrity. This classification is well-known and widely-accepted in the field of social organization settings [19]; and we believe it is also appropriate for consideration of trustworthiness in the SIoT environment.  
* _Ability_: is a dimension of trustworthiness showing the capability of a trustee to accomplish a trust goal. An entity may be high benevolent and integrity for fulfilling a trust goal but the results may not be satisfactory if it is not capable. This term incorporates some other terms that have been used as TAs in many trust-related literature such as competence, expertness, and credibility.
* _Benevolence_: is a dimension of trustworthiness showing to what extent a trustee is willing to do good things or not harm the trustor. Benevolence ensures that the trustee will have good intentions toward the trustor. This term incorporates some TAs such as credibility, relevance, and assurance as TAs.
* _Integrity_: is a dimension of trustworthiness showing the trustee adheres to a set of principles that helps the trustor believe that the trustee is not harmful and not betray what it has committed to do. These principles can come from various sources such as fairness, or morality. This term incorporates some TAs such as honesty, completeness, and consistency.  
Table 1 lists a miscellany of TAs keywords classified into the three categories. Some of the TAs in Table 1 are frequently used in trust literature ranging from social science to computer science, the other are rarely used and only existed in specific contexts. Even though each of the three factors Ability, Benevolence and Integrity captures some unique elements of trustworthiness, many of these keywords are not necessarily separated, and the interpretations of them clearly depend on particular environments and trust goals. For some specific environments and goals, certain TAs are similar whereas they are different in other contexts.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Ability TAs** & **Benevolence TAs** & **Integrity TAs** \\ \hline Competence, ability, capability, & Good intention, goodness, & Honesty, morality, completeness, \\ expertness, credibility, & certainty, cooperation, & consistency, accuracy, certainty, \\ predictability, timeliness, & cooperativeness, loyalty, & associativeness, responsiveness, faith, \\ robustness, safety, stability, & openness, caring, receptivity, & fulfilment, persistence, responsibility, \\ scalability, reliability, & assurance & tactfulness, sincerity, value \\ dependability & & congenality, accessibility \\ \hline \hline \end{tabular}
\end{table}
Table 1: Some keywords of trustworthiness from trust-related literatures classified into three dimensions.