Trust is a key component of relationships in social life. It is commonly argued that trust is the \glue" that holds families, societies,
organizations and companies together. In the literature trust is frequently considered as a strategic asset for organizations. Having a clear understanding
of the notion of trust and its components is paramount to both trust assessment and trust management. Although much progress has
been made to clarify the ontological nature of trust, the term remains overloaded and there is not yet a shared or prevailing, and conceptually
clear notion of trust. In this paper we address this issue by means of an in-depth ontological analysis of the notion of trust, grounded in the
Unified Foundational Ontology. As a result, we propose a concrete artifact, namely, the Reference Ontology for Trust, in which we characterize
the general concept of trust and distinguish between two types of trust, namely, social trust and institution-based trust. We also represent the
emergence of risk from trust relations. In addition, we make a comparative analysis of our Reference Ontology to other trust ontologies. To
validate and demonstrate the contribution of our approach, we apply it to model two application examples.
