Roles are entities that pervade our everyday life as well as biologists' and medical specialists' actual practice. Their nature nonetheless remains nebulous in spite of a large amount of recent research on it in various disciplines. This paper aims to provide an in-depth study of the term 'role' in alignment with an upper ontology Basic Formal Ontology (BFO). Closer examination reveals that the meanings of the term 'role' can be well disambiguated in terms of five BFO categories: a generically dependent continuant, a site, a role, a disposition, and a function. We also discuss the BFO characterization of role and its practical utility in the biomedical field with a focus on its relation with the BFO methodological principle of ontological realism and other BFO realizable entities: dispositions and functions.
Talk of roles is ubiquitous in our ordinary life and in a number
of different academic fields, ranging from knowledge
representation [
the role of a stone in marking a boundary [4, p. 100] the role of a magnet to attract iron objects the role of the heart to pump blood Roles are vital to biomedical ontologies at least in two respects.
First, the term ‘role’ is frequently used in the biomedical
literature: e.g., “the specific role of calcium in preventing
disease.” Second, healthcare systems would not be completely
accounted for unless their organizational structure is
wellspecified in terms of roles, or especially so-called ‘social roles’
[
Roles nevertheless remain nebulous entities, although they have
been extensively researched in foundational ontology research
for the last few decades [
Despite some endeavors to meet it [
In this paper we provide a close ontological investigation into
the meanings of the term ‘role’ with an emphasis its usage of the
term ‘role’. To do so, we exploit Basic Formal Ontology (BFO)
[
In the most basic BFO framework, entities fall into two kinds: universals (aka types, classes) and particulars (aka tokens, instances). Particulars (e.g., Mary) bear the instance-of relation to universals (e.g., Human). Particulars, on which we place a primary focus in this paper, fall into two categories: continuants and occurrents. Characteristically, continuants can persist, that is to say, they can exist at one time and also exist at another different time; whereas occurrents (including processes) extend through time. Continuants can be further divided into independent continuants (including objects) and dependent continuants (intuitively: properties). Independent continuants, or especially objects (e.g., stones) can be bearers of dependent
Copyright © 2019 for this paper by its author. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0). continuants (e.g., hardness) and they can also participate in occurrents (e.g., a fall of the stone).
For this purpose, we draw upon Toyoshima’s [
The paper is structured as follows. Section II presents
Toyoshima’s [
Section V concludes the paper with some brief remarks on future possible directions of research.
II.
Toyoshima [
This observation would lead to an analogy between a role and a
specification. The ontological nature of a specification remains
obscure, but Turner [
A role specification refers to a role that is understood by analogy
with a specification and role-bearing is interpreted as meeting a
role specification. On this specification view of role, a
rolebearer is to its role what an artifact is to its specification. In this
respect, roles and artifacts are closely linked from a modeling
perspective [
Despite their striking similarity, a role specification and a
specification (resp. a role-bearer and an artifact) differ greatly
from each other at least in two points. First, they are temporally
different: a role specification and a role-bearer are temporary
(time-relative) but a specification and an artifact are permanent
(time-insensitive). For instance, an American aircraft emerges
when it is built to the FAA specification and it continues to exist
until it is physically destroyed; whereas, Mary is a UB student as
long as she meets a UB-student role specification and she can
survive even after ceasing to be a student. Second and
connectedly, they are modally contrary: the former are
contingent (accidental) but the latter are necessary (essential).
(Note that, pace Fine [
Another possibility for understanding Mary’s studentness is based on the kind of situation in which Mary bears a student role. As a UB student, Mary can use various facilities and enjoy educational opportunities (e.g., taking classes). Mary’s studenteness may then consist in the fact that she locates herself in a specific ‘sphere’ or ‘position’ where she can do something role-related.
A role as conceptualized this way is analogous with a relative
place [
A role position means a role that is figured out by analogy to a
relative place and role-bearing is construed as occupying a role
position. Seen from this positional perspective, roles stand in
fixed ‘conceptual’ relations towards one or more entities, which
may be sometimes called ‘context’ in the relevant literature
[
In this section we delineate into which BFO category falls each
of the role triad (a role specification, a role position, and a role
performance) and other ontological accounts of the term ‘role’.
We also illustrate them with the examples (1)-(8) listed in
Section I. Note that this section draws partially upon Toyoshima
[
We introduce a fine-grained classification of dependent continuants for the sake of future argument. In BFO, there are two kinds of dependent continuants. One is a specifically dependent continuant: “A continuant entity that depends on precisely one independent continuant for its existence. The former is dependent on the latter in the sense that, if the latter ceases to exist, then the former will as a matter of necessity cease to exist also” [4, p. 185]. Examples include the mass of a kidney and the shape of a hand.
The other is a generically dependent continuant: “A continuant that is dependent on one or other independent continuants and can migrate from one bearer to another through a process of copying. We can think of generically dependent continuants as complex continuant patterns either of the sort created by authors or designers or (in the case of DNA sequences) brought into being through the processes of evolution” [4, p. 179]. Examples include the pdf file on Mary’s laptop and the pdf file that is a copy thereof on John’s laptop. Characteristically, a generically dependent continuants exists only if it is concretized in some counterpart specifically dependent continuant. To take one example, a paragraph of a novel in concretized in each pattern (quality) of ink on the pages of the printed novel.
One subtype of specifically dependent continuant is a realizable entity (subtypes of which are to be discussed in detail below): “A specifically dependent continuant entity that has at least one independent continuant as its bearer, and whose instances can be realized (manifested, actualized, executed) in associated processes of specific correlated types in which the bearer participates” [4, p. 183]. Examples include the role of being a doctor, the disposition of a fragile glass to break, and the function of a hammer to hit nails.
A)
A role specification would be most reasonably classified as a
generically dependent continuant. For one thing, a specification
is plausibly taken to be a generically dependent continuant.
Duncan [
Examples (1)-(3) are explicable in terms of a role specification as a generically dependent continuant (see [5, p. 101] concerning Examples (2)-(3)). In Example (1), a pilot role of a passenger means a generically dependent continuant whose bearers are passengers, or especially those who know well about the operation of the plane. In Example (2), the role of director of the institute depends generically on people (including Jane) with some qualifications (e.g., age and career). In Example (3), the particular role in the play can migrate among actors (such as Joe), e.g., with a certain level of acting proficiency.
B)
The BFO categorization of a role position would be more controversial than that of a role specification owing to the still unclear character of the former. A role position is however arguably most persuasively regarded as a site. A site is “a threedimensional immaterial entity that either (1) is (partially or wholly) bounded by a material entity or (2) is a threedimensional immaterial part of an entity satisfying (1)” [4, p. 112], where a material entity is an “independent continuant that has some portion of matter as part, is spatially extended in three dimensions, and that continues to exist through some interval of time, however short” [4, p. 180] and an immaterial entity is an “independent continuant that contains no material entities as parts” [ibid.]. Examples of sites include a rabbit hole, Mary’s nasal cavity, and a kangaroo pouch.
A site-based perspective on a role position has its advantages
and disadvantages. A site obviously represents the BFO way of
incorporating a relative place (see e.g., [
C)
It is not hard to see that a role potential accords well with the BFO category of role: “A realizable entity that (1) exists because the bearer is in some special physical, social, or institutional set of circumstances in which the bearer does not have to be, and (2) is not such that, if this realizable entity ceases to exist, then the physical make-up of the bearer is thereby changed. A role is thus always optional” [4, p. 184]. Given the BFO conception of role, for instance, Mary is a UB student in virtue of her student role that can be realized in, e.g., a process of her using a student discount. This would mean that a BFO-role is closely akin to a circumstantial ability, which underlies the idea of a role potential.
As said above, the potential view of role would require elucidation of roles and other comparable entities such as dispositions and functions. This issue is to be addressed in Section IV. In addition, it will be also discussed there the question of why BFO takes a potential-centered approach to role. Examples (5)-(6) are interpretable in terms of a role performance as a role. In Example (5), Jim’s nurse role is a role that can be realized in processes of his taking care of sick or injured people. In Example (6), the stone in question bears a role that can be realized in a process of boundary demarcation.
‘Role’ as a BFO-disposition We have above pondered three facets of role and their BFO categories, but the term ‘role’ may be too polysemous to be understood in terms of the ontological notion of role alone. Consider Example (7): ‘the role of a magnet to attract iron objects’. None of the role triad captures the meaning of the term ‘role’ of this example. In particular, a magnet attracts iron objects permanently and essentially rather than temporally and accidentally. We submit that, contrary to its linguistic surface, the term ‘role’ thereof refers to the BFO entity of disposition. A disposition is: “A realizable entity (a power, potential, or tendency) that exists because of certain features of the physical makeup [material basis] of the independent continuant that is its bearer” [4, p. 178, with our supplementary explanation]. A classical example of a disposition is fragility: the disposition to break when pressed with a certain force. More specifically, fragility of a glass is the disposition of the glass (bearer) to break (realization) that depends on a particular physical molecule structure (material basis) of the glass.
In BFO, dispositions sharply contrast with roles in terms of ‘groundedness’. Dispositions are internally grounded: if a disposition ceases to exist, then its bearer is physically changed. Roles are externally grounded in the sense that this is not the case; see the item (2) of the BFO definition of role. The BFO grounding differentiation between dispositions and roles would mesh with our temporal and modal one between artifactness and role. When a bearer (whether natural or artifactual) of a disposition fails to have the disposition, the bearer may sometimes (if not always) lose its essence. An aircraft would be no longer an aircraft when it loses a disposition to fly, for example. In that case, the disposition of a bearer determines the essence of the bearer (or at least serves to do so). In Example (7), a magnet has a disposition to attract iron objects and this disposition embodies the essence of the magnet. However, a bearer of a role is always the same physically even when the bearer loses that role, and a role is a mere accidental feature of its bearer. Mary remains physically unchanged when she is admitted to UB, and her studentness is (ontologically) irrelevant to her essential nature (which may be extremely difficult to define explicitly, though).
E)
‘Role’ as a BFO-function
The dispositional clarification of the term ‘role’ extends to the
BFO category of function because BFO, or precisely the latest
version of BFO (BFO 2.0) conceives function dispositionally
[
To illustrate this, consider Example (8): ‘the role of the heart to pump blood’. First of all, the heart has a disposition to pump blood: it depends on a certain organic structure of the heart and the heart would undergo physical change when it loses this disposition. Analyzed more meticulously, the disposition of the heart to pump blood is a function of the heart because it has emerged through evolutionary processes of the organism. To take another example, consider the phrase ‘the role of an aircraft to carry goods or passengers’. In ontological parlance, an aircraft has a function (but not a role) to carry good or passengers because the aircraft has been designed and produced to do so. A relationship between role and function is however further complicated by the issue of ‘use function’ to be addressed in Section IV.
A)
Although we have identified the five BFO meanings of the term
‘role’, questions remain about a detailed description of the BFO
conception of the role triad. Here three of them will be brought
up for discussion. First, why does BFO put a premium on a role
potential, as is supported by the finding that it is classified as a
role in BFO? Toyoshima [
Toyoshima [
Second, how can a role specification and a role position be
described or defined given the BFO performance-oriented view
of role? This amounts to the problem of what kind of generically
dependent continuant (resp. site) is a role specification (resp. a
role position), assuming the ontology-design method of the
Aristotelian definition [
Taking all this into consideration, first of all, it is reasonable to think that a role specification has as its bearer a bearer of a role and it is also concretized in the role of the bearer. Suppose for instance that, in Example (2), Bob was the sixth director of the institute. In this scenario, Jane’s director role differs from Bob’s, but they both concretize the same role specification to the effect that, e.g., a director of the institute is in charge of activities of the members of the institute. Next, informally speaking, a role position would be plausibly relativized to the context in which a certain independent continuant can have some role. It could be further added that a role position can be occupied by the rolebearer under discussion. In Example (4), a role position exists in relation with the brain and it was at first occupied by a healthy stellar neuron, but later it is by the pyramidal neuron. Finally, preliminary definitions of a role specification and a role position are provided as follows: •
BFO-role specification =def. a generically dependent continuant (i) whose bearer has a role and (ii) that is concretized in the role of the bearer. • BFO-role position =def. a site that (i) exists relative to the special physical, social, or institutional set of circumstances in virtue of which an independent continuant can have a role and (ii) can be occupied by the role-bearer.
It should be noted that the item (i) of the definition of a role position depends on part of the BFO existing definition of a role; and that a role position does not always need to be occupied by some role-bearer and it can be occupied by different role-bearers at different times. We intend to leave room for the flexibility of role positions so that they could help to solve some existing problems with a BFO-role (see below for details).
Third and lastly, why does BFO specify only the role-having
relation (has_role) but not the role-playing one [3, p. 58]? As is
indicated by Examples (1), (3), and (4), talk of role-playing is
quite commonplace in our everyday life. It is however
contentious whether and how the phrase ‘plays a role’ should be
taken with ontological seriousness (see e.g., [
There is a broad consensus on the high utility for ontologizing a
wide array of entities that is possessed by realizable entities,
ranging from the BFO subtypes of realizables [
First, a cloud of suspicion may hang over the ‘grounding distinction’ between roles and dispositions. Guarino [38, p. 17] asserts, for example: “I think that, especially for social roles, the corresponding attitudes/commitments/dispositions are not independent from the physical make-up of their bearer. For instance, the commitment to realize a student role of course requires some changes in the brain’s “make-up” of its bearer. I would say that, in general, active role-properties (being the lover of Mary) presuppose some (non-essential) change in the physical make-up of their role bearers, while this is not required for passive roles (being loved by John).” Paraphrased using the Mary-student example, the core of his argument is that Mary’s student role should not be a BFO-role (an externally grounded realizable entity) because there must be some physical change involved in Mary’s entering UB.
Although it may be a misinterpretation of a BFO-role, Guarino’s criticism would help to elucidate the difference between roles and dispositions. Quite important is the observation that the change (including emergence and disappearance) of roles are frequently concurrent with that of dispositions. To see this point, let us stipulate that Mary became more diligent after graduation from UB. It would appear that Mary’s assiduity was caused by her neural transformation, which was in turn by her student role. Actually, however, Mary’s diligence should be ascribed to the fact that Mary’s disposition to work hard was strengthened by realizations (e.g., taking classes at UB) of her student role which she no longer bears after graduation. On the other hand, Mary’s disposition to go to UB may have been greatly weakened when she lost her UB-student role.
Second, we have seen the cases in which the term ‘role’ refers to
a disposition or a function. One may wonder about their
opposite: the term ‘disposition’ or ‘function’ means a role when
coming under scrutiny. To the best of our knowledge, the term
‘disposition’ rarely, if ever, refers to a role; whereas greater care
may be needed to ensure that the term ‘function’ does not
designate a role. To illustrate the latter, consider the issue of ‘use
function’: roughly, the kind of functions that agents attribute to
objects in actually using them for their use purpose (see e.g.,
[
As was alluded to in Section I, roles are crucial for biomedical
ontologies, partly because of the widespread usage of the term
‘role’ in the biomedical literature, partly because of a growing
importance of social roles in ontologies of healthcare systems.
As for the former, we have explicated the term ‘role’ by
leveraging some existing BFO categories. This will help
biologists and medical specialists to understand correctly the
term ‘role’ and represent accurately its meaning on a
case-bycase basis when they build and/or ameliorate OBO ontologies.
We have also shown that the BFO potential-centered conception
of role is well-suitable for scientific ontologies in general. This
is all the more the case with biomedical ontologies for several
reasons. First, ontological realism is currently one of the most
prevailing approaches to biomedical ontologies [
As for the latter, our work will have implications for the
construction of social ontologies in the biomedical domain. For
one thing, there is general agreement among researchers in
social ontologies aligned with BFO that deontic entities (e.g.,
claims, obligations, and rights) are most appropriately classified
as generically dependent continuants that are concretized in
(social) roles, regardless of whether they are, more concretely,
socio-legal generically dependent continuants [
the role of a stone in marking a boundary
In the future we will be able to proceed along two main
directions of research. On the theoretical side, further
development is warranted of the BFO characterization of a role
specification and a role position, which will require in turn a
deeper understanding of a generically dependent continuant and a
site. Besides, further clarification should be given to complex
relationships between roles, dispositions, and function. On the
practical side, the utility of the BFO specification hitherto of the
term ‘role’ needs to be verified through its application to the
building and enhancement of biomedical ontologies, e.g., of
healthcare systems [