We start from the claim that trust in information sources is in fact just
a kind of social trust. We are interested in the fact that the relevance
and the trustworthiness of the information acquired by an agent X from
a source F, strictly depends and derives from the X's trust in F with
respect the kind of that information. Even if, of course, we have also to
consider the potential (positive and negative) interferences between this
information and the previous X's beliefs. In this paper, we analyze the
dierent dimensions of trust in information sources and formalize the
degree of subjective certainty or strength of the X's belief P, considering
three main factors: the X's trust about P just depending from the
X's judgement of the source's competence and reliability; the sources'
degree of certainty about P; and the X's degree of trust that P derives
from that given source. Finally we present a computational approach
based on fuzzy sets and some interesting examples of significant cases.
