BFO roles are realizable entities external to(i.e., not intrinsic to) the bearer. Roles are assigned to a bearer in a physical, social, or institutional set of circumstances and the bearer does not cease to exist when it stops bearing a role. Due to these reasons, a single bearer may bear multiple roles throughout its lifetime, e.g., the same person can be a buyer (iof:BuyerRole), a customer (iof:CustomerRole), and a supplier (iof:SupplierRole) at different time periods. But multiple roles can also be held concurrently by a single bearer. However, BFO does not provide a way to express the time when the bearer has started or stopped bearing a role and for how long the role was held.
To fill in these shortcomings, two new subclasses of bfo:process were introduced to IOF Core. Users can use the two processes to express exact or relative time points (relative to the time region the processes occupy) when a role has started or stopped to exist. However, flexibility is provided where the exact starting and stopping time points during the process are not required. This allows the user to choose a suitable scheme for representing the time of gaining and losing the role in a variety of ways per their data requirements. The classes are also axiomatized such that the bearer of the role is clear (as a participant in the process).