General Formal Ontology (GFO)
Given that the general approach to roles is initially independent of
other GFO categories, as well as the diversity of individuals
introduced as roles, leads us to question why all roles should fall
within the same category. Stated differently, what should the
intrinsic commonalities between processual and relational roles be?
We must admit that
there are none - a fact that lies in the nature of category ``role''
because, under a meta-level perspective, all general role characteristics apply to
These meta-level aspects further relate to the account of roles given by
Guarino (and colleagues), who characterizes ``role'' as a meta-category of
relationally dependent and anti-rigid categories
(41,28). The latter means that for
each instance of a role category, it is not essential to instantiate
that category. These criteria can be reconstructed in GFO, where
relational dependence corresponds to our contexts and anti-rigidity must
be re-interpreted in terms of player universals. Roles in GFO differ
from this approach in the sense that (1) there are role individuals, and
it may be essential to play a role. For instance, it is essential that the
natural number two is a factor of four, and it is likewise essential
that each human is a child. Anti-rigidity thus does not hold for every
player universal. Nevertheless, in most cases it is a useful indicator for
detecting player universals, and thus roles.