GFO Part I Basic Principles
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8.4 Process Classifications

Above we have presented two ways of classifying processes, first into as either discrete or continuous, and second as either simple or complex processes. However, neither is well suited as a general process classification, because the first case is a relative notion, whereas the second one is very structural in nature and appears useful from a technical point of view. Philosophical literature offers some other classifications which we analyze below.

Casati and Varzi (16) draw a classical distinction of what they call events (``things that happen``) between activities, achievements, accomplishments, and states20. This classification is summarized in table 1. The classification criteria are homogeneity, culmination, and instanteity. An event is homogeneous if the same description applies to its sub-events. Culmination is understood as having a natural finishing point. Instantaneity refers to the duration of the event.

Table: Types of events compiled according to (16)
Type of Event Homogeneity Culmination Instantaneity Example
Activity homogeneous never culminates extended in time John is walking uphill.
Accomplishment not homogeneous may culminate extended in time John is climbing a mountain.
Achievement not applicable is a culmination instantaneous John reaches to top of the mountain.
State homogeneous not applicable not applicable John knows the mountain.

Obviously, these types involve more kinds of occurrents than only processes. First, achievements appear to be extrinsic changes, as they are assumed to happen instantaneously. The choice of extrinsic changes, as opposed to intrinsic, is based on the notion of culmination which seems to refer to a realizable difference. States, as defined by Casati and Varzi (16) seem to refer to the realm of relations and facts, since there are no changes (in an intuitive sense) involved.

What remains are achievements and accomplishments, which are at least extended in time like processes. However, we doubt that these are an adequate classification of processes due to relying on the notion of homogeneity. Homogeneity is not a property of a process individual, but it is a property of some process universal, like walking. Neglecting granularity aspects, one can agree that all temporal parts of an individual walking are also instances of walking. However, this is not a property of the individual. For instance, we may extend the description to ``John walks from $A$ to $B$.'', which still refers to a walking, but more precisely to a walking from $A$ to $B$. The latter is no longer homogeneous, but it has the same instance.

Culmination allows for a similar argument. It seems to be based on identifying what can be derived at the end of the process. A culminating event is associated with an end point. This does not mean, however, that a non-culminating event does not have an end point. Each walking of John finds an end, and could thus also be classified as an accomplishment in the form, John walked to $X$.

For the above reasons, we refrain from accepting the distinction between achievements and accomplishments as a classification for process individuals, although we acknowledge that these terms refer to process universals. Note that difficult questions of the identity of processes touch the issues just discussed. Nevertheless, we will not address such issues, as they are not in the focus of this work.

Robert Hoehndorf 2006-10-18


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