Friendship in this sense is a symmetric relation, and transitive closure implies that
trust between friends is transitive. This is also reflected in the way we evaluate the
intentions of others. Our friends have positive intentions towards us. However, not
all friends are considered competent for a specific goal. There is no reason to expect
that ability is symmetric or transitive. We will investigate this issue in more detail in
the later chapters. Clearly, transitivity is an assumption that may apply to some trust
constructs but not all.
Similar considerations exist when computational trust is concerned. The cues
used to assess trust must be useful, and free of bias as much as possible. System
design must take into account how to correctly optimize for trust. For example,
a crowdsourcing system that makes previous votes available to voters introduces a
bias towards the votes of the earlier voters. There is reason not to trust such a system.
In our opinion, these issues impact trust computation greatly but have not yet been
discussed in great detail.
In summary, we must consider which cues are available to the trustor to judge
trust as well as the trustor's goals. Factors in the environment may impact how the
trustor's choices are framed and whether the trustor is primed to evalute them in a
specific way. The mental load and alertness of the trustor may impact which factors
will be evaluated. The order in which factors become available and are evaluated
may change the final trust evaluation. The relevant enviromental factors depend on
the trust constructs and trustees. Modeling these factors is an important part of any
A common norm in online sites is to complete a long chunk of text with a section
called tl;dr (Too Long Didn't Read). This section summarizes the trust context in a
few sentences to accommodate readers with limited cognitive resources.
The trust context defines who the trustor is and who the trustees are. The
dependence for a specific trusting choice specifies in detail which trustee to depend
on for which goal and how much. A utility is defined for each specific choice, which
in turn is used in defining trust.
However, to evaluate trust, a set of external cues regarding the trustees must be
used based on the environmental factors. Their evaluation is greatly impacted by
a set of external factors that need to be considered when modeling and measuring
1. C. Castelfranchi, R. Falcone, Trust Theory: A Socio-Cognitive and Computational Model
2. C. Dellarocas, Reputation mechanism design in online trading environments with pure moral
hazard. Inf. Syst. Res. 16 (2), 209-230 (2005)