General Formal Ontology (GFO)
Based on the literature, the following categories serve as contexts in
various role approaches: relations, processes, and (social) objects.
Accordingly, we distinguish three role types with the following
- A relational role corresponds to the way in which an
argument participates in some relation;
- A processual role corresponds to the manner in which a
single participant behaves in some process;
- A social role corresponds to the involvement of a
social object within some society.
Note that relational and processual roles have been discussed earlier,
in the sections on their corresponding context categories (see sect. 8 and 10, respectively). Here, we
focus on the relationships to the general role notions identified above.
Moreover, the given classification is not meant to be complete, i.e.,
other categories may be contexts, thus yielding further role
Relators are the contexts of relational roles, i.e., a relator can be
decomposed into at least two relational roles which complement each
other. Intuitively, the role-of relation seems like a part-of relation
in this case. Because relational roles refer to exactly one player, the
plays relation corresponds to has-property. Accordingly, relational
roles are subsumed by the category of properties.
Consider that the number two is a factor of
four. This refers to a relator with two role individuals, one instantiating
the role universal ``factor'', the other instantiating ``multiple''. The
first of these role individuals is played by two, while four plays the
second role individual.
The generality of relations regarding the entities they connect is
reflected in the fact that players of relational roles cannot be restricted
by any specific category; hence, the natural universal for relational roles
in general is the category ``entity''.
Processual roles have processes as their contexts. As such they are
processes themselves, and sect. 8.1 identifies them as
special layers of a process, because role-of is understood as a part-of
relationship (as in the case of relational roles). The plays relation is
different from plays for relational roles, because here plays corresponds to
participation in a process.
When John moves a pen, for example, the movement is a process in which John
and the pen are involved, in different ways. Accordingly, the process can be
broken into two roles, ``the mover'' and ``the moved''. John plays the
first role, the pen the second. Imagining John as a mime who pretends to
a pen should provide a natural illustration of the notion of processual
The case of the mime further exemplifies an uncommon case of roles:
a single processual role may itself form a context. Almost all role
notions are relational in nature, in the sense that their contexts are
composed of several roles. In contrast, processes that comprise
only a single participant are understood as a processual role, and
likewise, as a
context. Considering the plays relation, the potential players of processual
roles are restricted to persistants, because a persisting entity is
required to carve out roles from processes.
Note that the similarities of relational and processual roles leads to a
category of abstract roles. The latter is functionally defined as
providing ``a mechanism of viewing some entity –- namely the player -– in a
defined context'' (37). Given this abstraction, we can
now introduce a final type.
Social roles differ from abstract roles in that their understanding depends much
less on their context. Instead, social roles come with their
own properties and behavior, which is a common requirement in many role
approaches in computer science, cf. (55). For example,
if John is a student, he is issued a registration number and gains new
rights and responsibilities. From a philosophical perspective, this view
is further inspired by Searle (51) and the
ontological levels of Poli (45), see sect.
Social roles are considered to be social structures in GFO, which is an
analogous category to material structures, but in the social stratum.
However, social roles also need a foundation on the material level,
which in general role terms corresponds to the plays relation. For
instance, the human John plays a social role that is characterized by
specific rights and responsibilites. Note that so far we do not exclude
that social roles themselves may play other social roles; hence, there may
be chains of the plays relationship that must ultimately terminate by a
role played by a material structure.
The contexts of social roles are also social structures, which may be
called societies or institutions, cf. (51).
Accordingly, a rough similarity between role-of and part-of is present
for social roles as well. However, there are complex
interrelations among entities of the social stratum, and the ontology of
this stratum requires much more work.