Towards Representing Change in the BFO

The Basic Formal Ontology (BFO) is an upper ontology that embraces both continuants and occurrents. Continuants can persist through time while undergoing changes through their participation in processes. Processes are held not to change as they are said to <i>be</i> changes. Yet, the BFO is silent about what sorts of changes might exist: <i>history</i> is the only type that is subsumed by <i>process</i>. Although representing and tracking instance data by means of the BFO's time-indexed relations allows one to infer that some change must have happened in the portion of reality described by the data, change is not explicitly represented. When a change exists, there must be a change of something. However, when <i>the color of that flower</i> (a quality inhering in, but distinct from, <i>that flower</i>) instantiates red at one time, and brown at a later time, then that change, alone, is not a process under the current definitions and axioms of the BFO. This is because qualities can participate in a process p, but never by itself: p must have a material entity as participant. Furthermore, processes can only have other processes and process boundaries as parts; if the BFO would accept the change of qualities, or specifically dependent continuants in general, as occurrents, though not processes, then such change cannot be <i>occurrent-part-of</i> a process. In this paper we explore the basis of a theory, and the beginnings of an axiomatization thereof, as an extension to the BFO that recognizes <i>change</i> as a subtype of occurrent so that instances thereof <i>happen-in</i> processes and <i>happen-to</i> continuants whereby these continuants participate in the processes these changes <i>happen-in</i>. We anticipate re-expressing the ideas presented here as axioms expressed in terms of processes and participation in a future revision of the BFO-FOL axioms that currently prevent a tighter integration.