Abstract
The Unified Foundational Ontology (UFO-A) is a foundational ontology about endurants that has been built as a foundation for conceptual modeling, and which focuses on static aspects of endurants. In addition to UFO-A, we have the Unified Foundational Ontology–Part B (UFO-B), a formal theory dealing with the interplay between endurants and the dynamic aspects of reality (e.g., events, processes, causation, dispositions, situations). Given the objective of characterizing this interplay between endurants and perdurants, these two ontologies are meant to form an integral whole. However, currently, they diverge in the way they approach modality. While UFO-A uses a general notion of alethic modality without committing to any notion of time, UFO-B is centered around temporal aspects. As an attempt to address this issue, we here define a translation of the axioms of UFO-A to FOL, and revisit an excerpt of UFO-B in order to accommodate a partial order of time points. With the goal of producing a unified theory, we interpret the alethic modalities of necessity and contingency of UFO-A in terms of this temporal structure, paying a special attention to the interplay between the determinism of a causal nexus and the existence of counterfactual situations. The revisited UFO-B is called UFO-B? and the unified theory is called UFO-AB.