


Overview
General Formal Ontology (GFO)

Material persistants are particular universals whose instances are
material structures; they are related to those entities that are
sometimes called continuants or objects, as apples, cars or houses. Material
persistants represent the phenomenon of persistance through time of a material
object. A material
persistant satisfies a number of neccessary conditions. For every
material persistant , there exists a process such that
the set of instances of coincides with the set of processboundaries
of . This implies the existence of a chronoid ,
such that for every timepoint of , there exists exactly
one instance of at time point . Persistants exhibit a particular
kind of categorial abstraction over a collection of presentials that are
boundaries of processes. The construction of persistants seems to be
connected to the cognitive abilities of agents, human beings or animals.
^{13}^{14}
The complete specfication of a material structure, say an ordinary object,
integrates three aspects into
one system: the object as a presential, as a process, and as a persistant.
We explain and demonstrate this interrelation and integration using an
ontological analysis.
Consider an everyday name like ``John''.
What does John refer to in an ontologically precise sense?
There are, obviously, three possibilities, i.e.,
three entities of different categories:
 John denotes a presential
at some point in
time,
 John refers to a persistant , or
 the name is given to a process .
The following connections between these three entities can be stated.
Starting with an act of perception of John, we assume that
a presential is recognized, call it
. If one has seen John several times, with probably
varying properties, but still being able to identify him, this forms
the basis for a persistant, say . Now one may consider
the extension of this persistant (which is a universal), i.e., the
class
.
Obviously, the entity
referred to
above is a member of this class. Also, one can say that any two
members of that class represent ``the same John''.
In the third interpretation, the name John denotes a process
of a special kind. We postulate the existence of a process
whose set of projections to its timeboundaries equals the class of
instances of . Such processes are called
persistantprocesses, and they exhibit an integration of an
object (a continuant, a persistant) with a process. Furthermore, we see
that the presentials associated to John can be derived from a process
by taking the projections of this process to timeboundaries. On the other
hand, the persistant cannot be directly derived from a process
because a categorial abstraction must be taken into consideration.
Hence, the system
represents the complete
information about the entity whose name is ``John''.
The categorial abstraction over the presentialist Johns captures
an important aspect of John's personal identity.^{15}
Finally, we show that a complete understanding and decription of
concrete individuals needs all three aspects specified in
our integrative system. If one of these aspects is missing we will face
problems. If, for example, we consider John as a persistant only, then
this John cannot engage in any temporal action, for example, the
activity of eating. John's actions and activities are realized on the process
level. If we consider John as the set of all presentialist Johns, then we have
the same problem; since any action takes time a presentialist John cannot
carry out any action. If John is a process only, then the problem
becomes identifying the boundaries of the process because any natural process
may be prolonged both into the future and into the past. Furthermore, we perceive
John as a presential, which is missing in a pure processual understanding.
We face similar problems pertaining to a full understanding of
concrete entities, if we combine only two of the above
aspects.^{16}
Robert Hoehndorf
20061018

