The Unified Foundational Ontology (UFO), developed by Giancarlo Guizzardi and associates, incorporating developments from GFO, DOLCE and the Ontology of Universals underlying OntoClean in a single coherent foundational ontology. The core categories of UFO (UFO-A) have been completely formally characterized in Giancarlo Guizzardi’s Ph.D. thesis and further extended at the Ontology and Conceptual Modelling Research Group (NEMO) in Brazil with cooperators from Brandenburg University of Technology (Gerd Wagner) and Laboratory for Applied Ontology (LOA). UFO-A has been employed to analyze structural conceptual modeling constructs such as object types and taxonomic relations, associations and relations between associations, roles, properties, datatypes and weak entities, and parthood relations among objects. More recent developments incorporate an ontology of events in UFO (UFO-B), as well as an ontology of social and intentional aspects (UFO-C). The combination of UFO-A, B and C has been used to analyze, redesign and integrate reference conceptual models in a number of complex domains such as, for instance, Enterprise Modeling, Software Engineering, Service Science, Petroleum and Gas, Telecommunications, and Bioinformatics. Another recent development aimed towards a clear account of services and service-related concepts, and provided for a commitment-based account of the notion of service (UFO-S), UFO is the foundational ontology for OntoUML, an ontology modeling language.