=Paper=
{{Paper
|id=Vol-2931/ICBO_2019_paper_16
|storemode=property
|title=Roles and Their Siblings in Basic Formal Ontology
|pdfUrl=https://ceur-ws.org/Vol-2931/ICBO_2019_paper_16.pdf
|volume=Vol-2931
|authors=Fumiaki Toyoshima
|dblpUrl=https://dblp.org/rec/conf/icbo/Toyoshima19a
}}
==Roles and Their Siblings in Basic Formal Ontology==
https://ceur-ws.org/Vol-2931/ICBO_2019_paper_16.pdf
Roles and Their Siblings in Basic Formal Ontology
Fumiaki Toyoshimaa
a
Graduate School of Advanced Science and Technology, Japan Advanced Institute of Science and Technology, Nomi, Japan
Abstract disease.” Second, healthcare systems would not be completely
accounted for unless their organizational structure is well-
Roles are entities that pervade our everyday life as well as specified in terms of roles, or especially so-called ‘social roles’
biologists’ and medical specialists’ actual practice. Their nature [5,6]. Examples of those medical roles include healthcare
nonetheless remains nebulous in spite of a large amount of providers (e.g., doctors and pharmacists), receivers (e.g.,
recent research on it in various disciplines. This paper aims to patients), and policy makers (e.g., members of the World Health
provide an in-depth study of the term ‘role’ in alignment with an Organization). Therefore, a deeper understanding of roles will
upper ontology Basic Formal Ontology (BFO). Closer contribute to a robust construction and an effective utilization of
examination reveals that the meanings of the term ‘role’ can be biomedical ontologies.
well disambiguated in terms of five BFO categories: a
generically dependent continuant, a site, a role, a disposition, Roles nevertheless remain nebulous entities, although they have
and a function. We also discuss the BFO characterization of role been extensively researched in foundational ontology research
and its practical utility in the biomedical field with a focus on its for the last few decades [7]. For instance, it is a long-standing
relation with the BFO methodological principle of ontological issue whether there is any single definition of role, some prior
realism and other BFO realizable entities: dispositions and attempts [2,8] to offer it notwithstanding. Moreover, it is still a
functions. worthwhile challenge to provide a generic characterization of
multiple meanings of role within a single theoretical framework.
Keywords: Despite some endeavors to meet it [9,10], little careful
role, Basic Formal Ontology (BFO), ontological realism consideration has been given to a general ontology of roles vis-
à-vis the biomedical domain.
I. Introduction In this paper we provide a close ontological investigation into
the meanings of the term ‘role’ with an emphasis its usage of the
Talk of roles is ubiquitous in our ordinary life and in a number term ‘role’. To do so, we exploit Basic Formal Ontology (BFO)
of different academic fields, ranging from knowledge [3,4] as an upper ontology (aka foundational ontology), namely
representation [1] and conceptual modeling [2] to cognitive an ontology to furnish the most general categories (e.g., space
science and linguistics. Several examples of expressions and time) and relations (e.g., identity and parthood) to serve as a
comprising the term ‘role’ are listed below: useful guideline for building domain ontologies of high semantic
interoperability. The BFO-based exploration of the term ‘role’
1. A passenger plays the role of a pilot on a commercial would be of great value for biomedical ontologies because the
plane in an emergency. [3, p. 58] practical utility of BFO to them is shown by the achievement of
2. Jane’s being the seventh person to fill the role of the Open Biomedical Ontologies (OBO) Foundry [11]: a
director of this institute [4, p. 100] collaborative project to coordinate ontologies to support
biomedical data integration such that BFO can provide a
3. Joe’s being the third person to play a particular role in a common semantic basis for all the OBO ontologies.
play [4, p. 101]
In the most basic BFO framework, entities fall into two kinds:
4. A pyramidal neuron plays the role occupied by a universals (aka types, classes) and particulars (aka tokens,
damaged stellar neuron in the brain. [3, p. 58] instances). Particulars (e.g., Mary) bear the instance-of relation
5. Jim has the role of a nurse. [4, p. 100] to universals (e.g., Human). Particulars, on which we place a
primary focus in this paper, fall into two categories: continuants
6. the role of a stone in marking a boundary [4, p. 100] and occurrents. Characteristically, continuants can persist, that is
7. the role of a magnet to attract iron objects to say, they can exist at one time and also exist at another
different time; whereas occurrents (including processes) extend
8. the role of the heart to pump blood through time. Continuants can be further divided into
Roles are vital to biomedical ontologies at least in two respects. independent continuants (including objects) and dependent
First, the term ‘role’ is frequently used in the biomedical continuants (intuitively: properties). Independent continuants, or
literature: e.g., “the specific role of calcium in preventing 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 of the device, my device is defective relative to the specification
occurrents (e.g., a fall of the stone). of a stack” [14, pp. 16-17]. Quite importantly, Turner considers
specifications as intentional: “Our intentional stance determines
For this purpose, we draw upon Toyoshima’s [12] thesis that,
what we take to be the specification: something is a specification
based on a detailed analysis of upper ontologies, there are (at
if we give it normal force over the construction of an artefact”
least) three closely intertwined notions of role at a foundational
[13, p. 147].
level: a role specification, a role position, and a role potential. It
is found on closer examination that those three facets of roles A role specification refers to a role that is understood by analogy
(and other meanings of the term ‘role’) can be well-defined in with a specification and role-bearing is interpreted as meeting a
terms of some existing BFO categories. This would also testify role specification. On this specification view of role, a role-
to the explanatory force of BFO (with regard to roles) as bearer is to its role what an artifact is to its specification. In this
compared to its relative smallness among upper ontologies. respect, roles and artifacts are closely linked from a modeling
perspective [15]. In the U.S., for instance, an aircraft has to meet
The paper is structured as follows. Section II presents
the strict specification laid down by the Federal Aviation
Toyoshima’s [12] argument for three roles. Section III analyzes
Administration (FAA). This means that an aircraft-like
from the BFO viewpoint those three aspects of role and other
aggregate of mechanical parts is not an aircraft unless it is
possible meanings of the term ‘role’. Section IV discusses the
constructed exactly to the FAA specification. Likewise, UB has
BFO notion of role, its connections with the BFO principle of
drawn up intentionally its ‘student role specification’ (e.g.,
ontological realism as well as the BFO categories of disposition
admission requirements), and Mary fails to be a student (in other
and function, and its practical utility in the biomedical domain.
words: to bear a student role) unless she satisfies the UB-student
Section V concludes the paper with some brief remarks on
role specification.
future possible directions of research.
Despite their striking similarity, a role specification and a
specification (resp. a role-bearer and an artifact) differ greatly
II. Three Facets of Roles from each other at least in two points. First, they are temporally
different: a role specification and a role-bearer are temporary
Toyoshima [12] examines some preceding accounts of role, (time-relative) but a specification and an artifact are permanent
being motivated to know which ontological conception of role is (time-insensitive). For instance, an American aircraft emerges
suitable for which type of conceptual modeling. He then when it is built to the FAA specification and it continues to exist
hypothesizes that different theories of role might depend on until it is physically destroyed; whereas, Mary is a UB student as
different ‘role choices’ made by the theories: choices as to long as she meets a UB-student role specification and she can
which is most fundamental among ‘three facets’ of role (which survive even after ceasing to be a student. Second and
he calls the ‘role triad’), or its three main ontological connectedly, they are modally contrary: the former are
interpretations: namely, a role specification, a role position, and contingent (accidental) but the latter are necessary (essential).
a role potential. On his view, the role triad would defy explicit (Note that, pace Fine [16], we lightly assume throughout this
analysis, but it can be elucidated by analogy and illustrated with paper a conceptual overlap between modality and essentiality
the question of what it is supposed to mean to say, e.g., that merely for a practical purpose.) While artifactness (e.g., FAA-
Mary is a student of University at Buffalo (UB), given the fact aircraftness) constitutes the essence of an American aircraft, for
that a student is taken to be a paradigmatic example of role and example, roleness (e.g., UB-studentness) is inessential to Mary.
Mary bears a student role, or simply Mary is a role-bearer. It must be emphasized that temporality and
contingency/accidentality are key characteristics of a general
A) Role Specification notion of role irrespective of which role choice is taken.
One approach to Mary’s studentness focuses on the deontic or B) Role Position
normative dimension of her student role. Mary must gain
admission to UB in order to become a UB student. To enjoy a Another possibility for understanding Mary’s studentness is
full-time student status, she needs to register for a certain based on the kind of situation in which Mary bears a student
number of credit hours per semester. She is also required to role. As a UB student, Mary can use various facilities and enjoy
defend her dissertation to obtain a doctoral degree from UB. educational opportunities (e.g., taking classes). Mary’s
Mary’s studentness is thus explicable in terms of the satisfaction studenteness may then consist in the fact that she locates herself
of the constraints or conditions that are, so to speak, ‘embedded’ in a specific ‘sphere’ or ‘position’ where she can do something
in her student role. role-related.
This observation would lead to an analogy between a role and a A role as conceptualized this way is analogous with a relative
specification. The ontological nature of a specification remains place [17]. Given the Newtonian conception of absolute space,
obscure, but Turner [13] maintains insightfully that a both absolute places and relative places persist and may be
specification is something that has “correctness jurisdiction over occupied by various (material) objects at various times. Unlike
an artefact” [13, p. 147]. By ‘correctness jurisdiction’ he means absolute places (which are parts of absolute space that are
that the specification places “empirical demands on the physical independent of objects), relative places stand in fixed spatial
device” [13, p. 144]. If an artifact is not built to a certain relations with one or more objects (reference objects [17]).
specification, the artifact is defective with respect to that Examples include places in and around a ship whose reference
specification. Duncan [14] illustrates this point as follows: “For object is the ship.
example, if I build a physical implementation of a stack and the
device does not allow me to add and remove items from the top 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 We introduce a fine-grained classification of dependent
fixed ‘conceptual’ relations towards one or more entities, which continuants for the sake of future argument. In BFO, there are
may be sometimes called ‘context’ in the relevant literature two kinds of dependent continuants. One is a specifically
[10,18]. (Note that, despite Smith’s [19] warning against dependent continuant: “A continuant entity that depends on
concepts in ontology research, we are using the term precisely one independent continuant for its existence. The
‘conceptual’ in its broad sense as a kind of placeholder. Its former is dependent on the latter in the sense that, if the latter
precise meaning should be further clarified in the future ceases to exist, then the former will as a matter of necessity
investigation.) In bearing a UB-student role, for example, Mary cease to exist also” [4, p. 185]. Examples include the mass of a
occupies the student role position that exists relative to UB. kidney and the shape of a hand.
The analogy between role positions and relative places would The other is a generically dependent continuant: “A continuant
shed light on the alleged relational nature of roles [7,8,20]. One that is dependent on one or other independent continuants and
salient feature of relative places is that they may move relative can migrate from one bearer to another through a process of
to one another when their reference objects move relative to one copying. We can think of generically dependent continuants as
another. Using Donnelly’s [17] example, when a ship moves complex continuant patterns either of the sort created by authors
relative to the earth, places with the ship as their reference object or designers or (in the case of DNA sequences) brought into
(e.g. the ship’s hold) move relative to places with the earth as being through the processes of evolution” [4, p. 179]. Examples
their reference object. In a similar vein, role positions may include the pdf file on Mary’s laptop and the pdf file that is a
‘conceptually move’ relative to one another when their contexts copy thereof on John’s laptop. Characteristically, a generically
‘conceptually move’ relative to one another. For instance, when dependent continuants exists only if it is concretized in some
a human resource department changes its importance with counterpart specifically dependent continuant. To take one
respect to its company, personnel director role positions (whose example, a paragraph of a novel in concretized in each pattern
context is the human resource department) change their (quality) of ink on the pages of the printed novel.
relationship with executive role positions (whose context is the
One subtype of specifically dependent continuant is a realizable
company).
entity (subtypes of which are to be discussed in detail below):
C) Role Potential “A specifically dependent continuant entity that has at least one
independent continuant as its bearer, and whose instances can be
Yet another interpretation of Mary’s studentness builds upon the realized (manifested, actualized, executed) in associated
ability of Mary to do something role-associated (which is processes of specific correlated types in which the bearer
sometimes informally called ‘circumstantial possibility’). Since participates” [4, p. 183]. Examples include the role of being a
she is a UB student, Mary can do many things (e.g., getting a doctor, the disposition of a fragile glass to break, and the
student discount). She is able to acquire a degree from UB, function of a hammer to hit nails.
whereas non-UB students are not. Mary’s studentness would be
explainable in terms of the potential that she can have in bearing A) Role Specification as a BFO-generically Dependent
a student role. Continuant
A role potential designates a role that is thought of as a sort of A role specification would be most reasonably classified as a
circumstantial ability and role-bearing is translated as having a generically dependent continuant. For one thing, a specification
role potential. It is important to remark that a role-bearer has is plausibly taken to be a generically dependent continuant.
only to possess the role-related ability instead of demonstrating Duncan [14] analyzes Turner’s [13] conception of specification
it actually. To remain a UB student (i.e., to bear a UB-student on the basis of BFO and contends that it is a kind of information.
role), Mary does not need to use any student discount; it is only To our eyes, information is naturally seen as a generically
necessary that she be able to do it. dependent continuant because it obeys the ‘rule of migration’.
A role potential may be easiest to understand in the role triad For another, an ontological theory of role that endorses
because it is intuitively grasped as a special kind of ability and explicitly a role specification can be construed in the BFO
avoids complications added by analogies with the complex fashion as a commitment to the view that a role is a generically
notions such as a specification (in the case of a role dependent continuant. Masolo et al. [8] propose a general
specification) and a relative place (in the case of a role position). framework for social roles in compliance with an upper ontology
In contrast, a role potential should be treated with the utmost the Descriptive Ontology for Linguistic and Cognitive
caution because it could be otherwise conflated with other Engineering (DOLCE) [21]. At the nub of their argument is that
apparently similar but different entities, viz. dispositions and social roles are fundamentally characterized by the DOLCE
functions (see Section IV for details on this point). entity of description. As Toyoshima [12] argues, they take a
specification approach to role and a DOLCE-description could
be well conceived as a generically dependent continuant that is
III. Roles and Their Siblings in BFO
connected to agents’ intentionality.
In this section we delineate into which BFO category falls each Examples (1)-(3) are explicable in terms of a role specification
of the role triad (a role specification, a role position, and a role as a generically dependent continuant (see [5, p. 101] concerning
performance) and other ontological accounts of the term ‘role’. Examples (2)-(3)). In Example (1), a pilot role of a passenger
We also illustrate them with the examples (1)-(8) listed in means a generically dependent continuant whose bearers are
Section I. Note that this section draws partially upon Toyoshima passengers, or especially those who know well about the
[12] (especially its Section 4.3). 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 D) ‘Role’ as a BFO-disposition
particular role in the play can migrate among actors (such as
Joe), e.g., with a certain level of acting proficiency. We have above pondered three facets of role and their BFO
categories, but the term ‘role’ may be too polysemous to be
B) Role Position as a BFO-site understood in terms of the ontological notion of role alone.
Consider Example (7): ‘the role of a magnet to attract iron
The BFO categorization of a role position would be more objects’. None of the role triad captures the meaning of the term
controversial than that of a role specification owing to the still ‘role’ of this example. In particular, a magnet attracts iron
unclear character of the former. A role position is however objects permanently and essentially rather than temporally and
arguably most persuasively regarded as a site. A site is “a three- accidentally. We submit that, contrary to its linguistic surface,
dimensional immaterial entity that either (1) is (partially or the term ‘role’ thereof refers to the BFO entity of disposition. A
wholly) bounded by a material entity or (2) is a three- disposition is: “A realizable entity (a power, potential, or
dimensional immaterial part of an entity satisfying (1)” [4, p. tendency) that exists because of certain features of the physical
112], where a material entity is an “independent continuant that makeup [material basis] of the independent continuant that is its
has some portion of matter as part, is spatially extended in three bearer” [4, p. 178, with our supplementary explanation]. A
dimensions, and that continues to exist through some interval of classical example of a disposition is fragility: the disposition to
time, however short” [4, p. 180] and an immaterial entity is an break when pressed with a certain force. More specifically,
“independent continuant that contains no material entities as fragility of a glass is the disposition of the glass (bearer) to break
parts” [ibid.]. Examples of sites include a rabbit hole, Mary’s (realization) that depends on a particular physical molecule
nasal cavity, and a kangaroo pouch. structure (material basis) of the glass.
A site-based perspective on a role position has its advantages In BFO, dispositions sharply contrast with roles in terms of
and disadvantages. A site obviously represents the BFO way of ‘groundedness’. Dispositions are internally grounded: if a
incorporating a relative place (see e.g., [22,23]), and it would be disposition ceases to exist, then its bearer is physically changed.
straightforward to label a role position as a site. On the other Roles are externally grounded in the sense that this is not the
hand, a role position would be considerably different from a site case; see the item (2) of the BFO definition of role. The BFO
in the sense of not being explicitly bound or demarcated in grounding differentiation between dispositions and roles would
relation to material entities. In the Mary-student example, it mesh with our temporal and modal one between artifactness and
might be possible to think that Mary’s role position is the kind role. When a bearer (whether natural or artifactual) of a
of site that is formed with respect to physical buildings disposition fails to have the disposition, the bearer may
possessed by UB, but only with a worry over a somewhat sometimes (if not always) lose its essence. An aircraft would be
arbitrary reification of role positions. It is nonetheless equally no longer an aircraft when it loses a disposition to fly, for
true that there is no other promising BFO-categorical candidate example. In that case, the disposition of a bearer determines the
for a role position. Finally, Example (4) can be well explained essence of the bearer (or at least serves to do so). In Example
from the viewpoint of a role position as a site: the role of the (7), a magnet has a disposition to attract iron objects and this
damaged stellar neuron refers to a site that is identified relative disposition embodies the essence of the magnet. However, a
to the brain (context) and it is now ‘occupied’ by the pyramidal bearer of a role is always the same physically even when the
neuron. bearer loses that role, and a role is a mere accidental feature of
its bearer. Mary remains physically unchanged when she is
C) Role Potential as a BFO-role admitted to UB, and her studentness is (ontologically) irrelevant
It is not hard to see that a role potential accords well with the to her essential nature (which may be extremely difficult to
BFO category of role: “A realizable entity that (1) exists because define explicitly, though).
the bearer is in some special physical, social, or institutional set E) ‘Role’ as a BFO-function
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 The dispositional clarification of the term ‘role’ extends to the
physical make-up of the bearer is thereby changed. A role is thus BFO category of function because BFO, or precisely the latest
always optional” [4, p. 184]. Given the BFO conception of role, version of BFO (BFO 2.0) conceives function dispositionally
for instance, Mary is a UB student in virtue of her student role [24] (see [25,26] for criticism): “A function is a special kind of
that can be realized in, e.g., a process of her using a student disposition. It is a realizable entity whose realization is an end-
discount. This would mean that a BFO-role is closely akin to a directed activity of its bearer that occurs because this bearer is
circumstantial ability, which underlies the idea of a role (a) of a specific kind and (b) in the kind or kinds of contexts that
potential. it is made or selected for. Thus a function is a disposition that
As said above, the potential view of role would require exists in virtue of the bearer’s physical make-up, and this
elucidation of roles and other comparable entities such as physical make-up is something the bearer possesses because of
dispositions and functions. This issue is to be addressed in how it came into being --- either through natural selection (in the
Section IV. In addition, it will be also discussed there the case of biological entities) or through intentional design (in the
question of why BFO takes a potential-centered approach to case of artifacts)” [4, pp. 102-103].
role. Examples (5)-(6) are interpretable in terms of a role To illustrate this, consider Example (8): ‘the role of the heart to
performance as a role. In Example (5), Jim’s nurse role is a role pump blood’. First of all, the heart has a disposition to pump
that can be realized in processes of his taking care of sick or blood: it depends on a certain organic structure of the heart and
injured people. In Example (6), the stone in question bears a role the heart would undergo physical change when it loses this
that can be realized in a process of boundary demarcation. disposition. Analyzed more meticulously, the disposition of the
heart to pump blood is a function of the heart because it has Aristotelian definition [32] where a term can be defined by dint
emerged through evolutionary processes of the organism. To of a genus (as a species with a differentia). The identity of a
take another example, consider the phrase ‘the role of an aircraft generically dependent continuant is a highly debatable topic (see
to carry goods or passengers’. In ontological parlance, an aircraft e.g., [6,33,34]); and so is a site (but see [17] for some thoughts).
has a function (but not a role) to carry good or passengers We can safely say however that both of the definitions of a role
because the aircraft has been designed and produced to do so. A specification and a role position should comprise the BFO term
relationship between role and function is however further ‘role’ since it is so paramount as to ground all other role-related
complicated by the issue of ‘use function’ to be addressed in notions in BFO; and that a role specification needs to be
Section IV. constrained at least by its bearer and its concretization, and a
role position at least by which material entity bounds or
demarcates it.
IV. Discussion
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
A) The Role Triad in BFO and Ontological Realism
and it is also concretized in the role of the bearer. Suppose for
Although we have identified the five BFO meanings of the term instance that, in Example (2), Bob was the sixth director of the
‘role’, questions remain about a detailed description of the BFO institute. In this scenario, Jane’s director role differs from Bob’s,
conception of the role triad. Here three of them will be brought but they both concretize the same role specification to the effect
up for discussion. First, why does BFO put a premium on a role that, e.g., a director of the institute is in charge of activities of
potential, as is supported by the finding that it is classified as a the members of the institute. Next, informally speaking, a role
role in BFO? Toyoshima [12] holds that there is a strong position would be plausibly relativized to the context in which a
correlation between role choices of upper ontologies and their certain independent continuant can have some role. It could be
meta-ontological choices [27]: roughly, choices that are further added that a role position can be occupied by the role-
fundamental enough to determine ontological choices [21], bearer under discussion. In Example (4), a role position exists in
namely choices as to whether and how a certain ontological relation with the brain and it was at first occupied by a healthy
category or relation is adopted. The DOLCE theory of role stellar neuron, but later it is by the pyramidal neuron. Finally,
focuses on a role specification, for instance, because DOLCE preliminary definitions of a role specification and a role position
aims to represent categories with a clear cognitive bias that are are provided as follows:
associated with e.g., human cognition and socio-cultural artifacts • BFO-role specification =def. a generically dependent
(which is a DOLCE meta-ontological choice), and a role continuant (i) whose bearer has a role and (ii) that is
specification is arguably the most cognitive and/or linguistic concretized in the role of the bearer.
way of understanding roles in the sense of emphasizing their
intentional aspect. • BFO-role position =def. a site that (i) exists relative to
the special physical, social, or institutional set of
Toyoshima [12] attributes the BFO role choice of a role circumstances in virtue of which an independent
potential to the BFO meta-ontological adoption of ontological continuant can have a role and (ii) can be occupied by
realism [28] (see [29,30] for criticism): “The realist the role-bearer.
methodology is based on the idea that the most effective way to
It should be noted that the item (i) of the definition of a role
ensure mutual consistency of ontologies over time and to ensure
position depends on part of the BFO existing definition of a role;
that ontologies are maintained in such a way as to keep pace and that a role position does not always need to be occupied by
with advances in empirical research is to view ontologies as some role-bearer and it can be occupied by different role-bearers
representations of the reality that is described by science. This is at different times. We intend to leave room for the flexibility of
the fundamental principle of ontological realism” [28, p. 139]. It role positions so that they could help to solve some existing
is a rather complicated matter to assess exactly what ontological problems with a BFO-role (see below for details).
realism entails (see e.g., [31]), but one plausible corollary of this
policy would be that BFO-based ontologies should maximize Third and lastly, why does BFO specify only the role-having
symbiosis with empirically scientific inquiry, which would relation (has_role) but not the role-playing one [3, p. 58]? As is
imply in turn that the BFO notion of role should be consistent indicated by Examples (1), (3), and (4), talk of role-playing is
quite commonplace in our everyday life. It is however
with scientific activities. This results reasonably in the BFO
contentious whether and how the phrase ‘plays a role’ should be
choice of a role potential because scientists typically focus on taken with ontological seriousness (see e.g., [35]). One tenable
the structure and behavior of the natural world. To investigate idea would be that role-playing conveys the level of achievement
the human mind, for instance, contemporary cognitive scientists of role-related goals. Mary’s behavior is evaluable by a criterion
and psychologists tend to highlight the importance of people’s (e.g., obtained credits) for being a student, for instance. Different
behaviors such as their facial expressions and actions. Taken role choices would yield different understandings of role-playing,
with a scientific attitude, roles (e.g., Mary’s student role) would namely as meeting a role specification, as occupying a role
be preferably ontologized in terms of externally observable position, or as having a role potential. Characteristic of the BFO
performances of role-bearers (e.g., Mary’s using a student construal of role is to reduce the alleged role-playing to
discount). realization. Mary’s student actions are explicable in terms of
realizations of her student role. Accordingly, BFO only needs the
Second, how can a role specification and a role position be standard property-having relation (one subtype of which is the
described or defined given the BFO performance-oriented view has_role relation), instead of a new primitive role-playing one.
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
B) Roles, Dispositions, and Functions C) Roles in Biomedical Ontologies
There is a broad consensus on the high utility for ontologizing a As was alluded to in Section I, roles are crucial for biomedical
wide array of entities that is possessed by realizable entities, ontologies, partly because of the widespread usage of the term
ranging from the BFO subtypes of realizables [36] (i.e., ‘role’ in the biomedical literature, partly because of a growing
dispositions, functions, and roles) to other kinds of realizables importance of social roles in ontologies of healthcare systems.
(e.g., tendencies [37]). It is nevertheless a highly controversial As for the former, we have explicated the term ‘role’ by
subject how BFO-realizables are to be individuated. It would be leveraging some existing BFO categories. This will help
indeed valuable to elaborate on a comparatively revisionary biologists and medical specialists to understand correctly the
classification of BFO-realizables (see e.g., [25]). To simplify the term ‘role’ and represent accurately its meaning on a case-by-
matter, however, we will confine ourselves to two topics case basis when they build and/or ameliorate OBO ontologies.
regarding the interrelationships between roles and other two
We have also shown that the BFO potential-centered conception
realizable entities while retaining the present, BFO 2.0
of role is well-suitable for scientific ontologies in general. This
characterization of them.
is all the more the case with biomedical ontologies for several
First, a cloud of suspicion may hang over the ‘grounding reasons. First, ontological realism is currently one of the most
distinction’ between roles and dispositions. Guarino [38, p. 17] prevailing approaches to biomedical ontologies [40]. Second,
asserts, for example: “I think that, especially for social roles, the BFO-roles are relatively understandable for biomedical experts
corresponding attitudes/commitments/dispositions are not because they are closely akin to dispositions, which are central
independent from the physical make-up of their bearer. For to biomedicine [37] and serve as a useful conceptual tool for an
instance, the commitment to realize a student role of course ontological analysis of the explanatory practice in biomedicine
requires some changes in the brain’s “make-up” of its bearer. I from both theoretical [41] and practical [42,43,44] points of
would say that, in general, active role-properties (being the lover view. Third, it has been pointed out that “many so-called
of Mary) presuppose some (non-essential) change in the physical functions in biomedical ontologies are, strictly speaking, roles”
make-up of their role bearers, while this is not required for [25, p. 11].
passive roles (being loved by John).” Paraphrased using the
As for the latter, our work will have implications for the
Mary-student example, the core of his argument is that Mary’s
construction of social ontologies in the biomedical domain. For
student role should not be a BFO-role (an externally grounded
one thing, there is general agreement among researchers in
realizable entity) because there must be some physical change
social ontologies aligned with BFO that deontic entities (e.g.,
involved in Mary’s entering UB.
claims, obligations, and rights) are most appropriately classified
Although it may be a misinterpretation of a BFO-role, Guarino’s as generically dependent continuants that are concretized in
criticism would help to elucidate the difference between roles (social) roles, regardless of whether they are, more concretely,
and dispositions. Quite important is the observation that the socio-legal generically dependent continuants [45] or directive
change (including emergence and disappearance) of roles are information entities [46] or others. Deontic entities as construed
frequently concurrent with that of dispositions. To see this point, this way can be viewed as a subtype of role specifications; and
let us stipulate that Mary became more diligent after graduation in this regard, we might have discussed in some way a
from UB. It would appear that Mary’s assiduity was caused by theoretical foundation for deontic entities in social ontology.
her neural transformation, which was in turn by her student role.
For another, it is nowadays fairly popular to model organizations
Actually, however, Mary’s diligence should be ascribed to the
(totally or partially) upon interrelations among roles in various
fact that Mary’s disposition to work hard was strengthened by
disciplines, including multiagent systems [47,48] and
realizations (e.g., taking classes at UB) of her student role which
foundational ontology research [49,50,51]. It is sometimes
she no longer bears after graduation. On the other hand, Mary’s
claimed however that the BFO conception of role fits badly with
disposition to go to UB may have been greatly weakened when
this approach because it faces what may be called the ‘problem
she lost her UB-student role.
of non-transferability’ [46] or especially the ‘problem of vacant
Second, we have seen the cases in which the term ‘role’ refers to (empty) role’. Being postulated to be represented by a
a disposition or a function. One may wonder about their configuration of roles, an organization should remain the same
opposite: the term ‘disposition’ or ‘function’ means a role when even when there exists a ‘vacant role’: a role to be beard by
coming under scrutiny. To the best of our knowledge, the term nobody. Recall an extensive story of Example (2) in Section IV-
‘disposition’ rarely, if ever, refers to a role; whereas greater care A: the structure of the institute has not changed itself since Bob
may be needed to ensure that the term ‘function’ does not resigned as the sixth director until Jane is newly elected as the
designate a role. To illustrate the latter, consider the issue of ‘use seventh director. BFO-roles would nonetheless seem to embrace
function’: roughly, the kind of functions that agents attribute to the discrepancy between the real structure of an organization and
objects in actually using them for their use purpose (see e.g., its ‘role structure’ because they have to depend specifically on
[39] for more details). If Mary uses a screw driver to open her individual agents (such as Bob and Jane) and they are thus non-
paint cans, for instance, it has the use function to open paint cans transferable. The issue of vacant role is still unresolved, but one
[25]. In spite of an ongoing discussion about BFO-functions, the possible answer to this question may be to ground an
disputants generally acknowledge that use functions should be organizational structure upon a constellation of role positions
categorized as roles because they are ‘accidental functions’: they (rather than roles) of the organization because role positions
have nothing to do with the essence of their bearers [24,25]. thereof, by definition, exist even in the case of vacant roles,
insofar as does the organization. Our complete solution to the
general problem of non-transferability will require not only
clearer delineation of the idea of a role position but also careful
ontological consideration of the identity of organizations (see Guarino [38, p. 14] states that it “reflects a very peculiar
e.g., [52]). understanding of the role notion which, although useful, would
require a broader framework”. We hope that our argument over
BFO-roles and their sibling entities will dispel this kind of worry.
V. Conclusion
To summarize, we examined within the BFO framework the Address for correspondence
meanings of the term ‘role’. We also discussed the BFO
potential-oriented conception of role as an externally grounded Fumiaki Toyoshima. E-mail: toyo.fumming@gmail.com;
realizable entity with a focus on its connections with ontological fumiakit@buffalo.edu.
realism, dispositions, and functions as well as its usefulness for
an ontological modeling in the biomedical field. We ended up References
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