=Paper=
{{Paper
|id=Vol-2050/foust-paper4
|storemode=property
|title=YAMATO: Yet Another More Advanced Top-Level
Ontology with Analysis of Five Examples of Change
|pdfUrl=https://ceur-ws.org/Vol-2050/FOUST_paper_4.pdf
|volume=Vol-2050
|authors=Riichiro Mizoguchi,Fumiaki Toyoshima
|dblpUrl=https://dblp.org/rec/conf/jowo/MizoguchiT17
}}
==YAMATO: Yet Another More Advanced Top-Level
Ontology with Analysis of Five Examples of Change==
https://ceur-ws.org/Vol-2050/FOUST_paper_4.pdf
YAMATO: Yet Another More Advanced
Top-level Ontology with Analysis of Five
Examples of Change
Riichiro MIZOGUCHI a,1 and Fumiaki TOYOSHIMA b,2
a Research Center for Service Science, Japan Advanced Institute of Science and
Technology (JAIST), Nomi, Japan
b Graduate School of Advanced Science and Technology, Japan Advanced Institute of
Science and Technology (JAIST), Nomi, Japan
Abstract. A late-comer upper ontology YAMATO is summarized in this paper.
YAMATO distinguishes itself from the other existing upper ontologies in the follow-
ing respects. (1) One of its most salient features is that it is designed with both en-
gineering and philosophical minds. (2) Because the world is full of roles, it is based
on a solid theory of roles. (3) In order to deal with artifacts effectively, YAMATO
has a sophisticated theory of functions. (4) Information is another kind of entity
which differs from entities that philosophers have traditionally discussed to date
in the sense of being a content-bearing thing. Considering the modern society in
which a flood of information occurs, YAMATO also has a theory of informational
objects (representations). (5) Quality and quantity are carefully organized for inter-
operability of real-world data. (6) Its philosophical contribution includes a theory
of objects, processes and events. YAMATO has been intensively applied through the
exploitation of those features. Five cases given by the organizers of the first edition
of FOUST workshop are analyzed to demonstrate how YAMATO models the real
world.
Keywords. YAMATO, foundational ontology, ontological analysis, formal ontology
1. Introduction
Upper ontology is the core of ontology engineering. It plays a key role in ontology devel-
opment by giving developers a guideline about how to view the target domain. There al-
ready exist several well-designed upper ontologies such as DOLCE [1], BFO [2], GFO [3],
and UFO [4]. It seems that there is no need to add yet another upper ontology. The paper
summarizes the reason why we adventure to develop a new upper ontology YAMATO [5]
(Yet Another More Advanced Top-level Ontology). YAMATO was developed to make
up for what the existing upper ontologies badly mishandle. Although it is currently be-
ing axiomatized and is not yet fully so, YAMATO is implemented in the ontology editor
Hozo3 and OWL. It is freely available for use.4
1 Corresponding Author: Riichiro Mizoguchi, Research Center for Service Science, Japan Advanced
Instituite of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292, Japan; E-mail:
mizo@jaist.ac.jp.
2 fumiaki.toyoshima@jaist.ac.jp
3 http://www.hozo.jp/
4 http://www.ei.sanken.osaka-u.ac.jp/hozo/onto library/upperOnto.htm
YAMATO claims to reveal secrets of reality so well that its utility in practice can be
maximized, although some might criticize its structure for being too large and complex.
If users think it specifies too much detail, they can use only categories down to the level
which they think is appropriate from the top level by neglecting the rest of those at lower
levels. Many of the existing upper ontologies do not seem good enough for explaining
reality or for guiding domain people to help them build ontologies. What they need are
not only the distinction between objects and qualities but also that between quality and
quantity and that between quality and a description of quality; not only the distinction
between objects and representation but also that between a copy of book and a book one
writes and that between a novel and a musical score; and not only the distinction between
process and event but also that between a pulse and a sequence of pulses and that between
to separate and to cut. They also need to know how much similar a procedure and a piece
of music are in what sense, why events cannot change while processes can, etc. YAMATO
is designed to answer all of the above questions and the like.
This paper illustrates YAMATO with five-case analyses to discuss how it models
a couple of crucial things for future comparison with other existing upper ontologies.
The organization of this paper is based on the specified format of the first workshop of
FOUST. In particular, five cases discussed in Section 3 are given by the workshop orga-
nizers and they concern various kinds of change in the real world. The heart of YAMATO
is summarized below:
(1) YAMATO is designed with both engineering and philosophical minds. It accepts
fundamental distinctions such as continuant vs. occurrent, independent entity vs. depen-
dent entity, and quality vs. quantity as well as several meta-level properties such as in-
tegrity, unity, dissectivity to define fundamental types. For example, an object is defined
as an integral, unitary and non-dissective continuant, and a continuant is defined as any-
thing which enacts its external processes. It adopts strict single inheritance in is-a hier-
archy which is organized according to the rigid definition of is-a and instance-of rela-
tions based on the set membership with the notion of essential property.5 Thus it does
not allow to put a role under an independent entity in is-a hierarchy, e.g., teacher cannot
be subsumed by person. It accepts the theory of entity stacking to deal with the issue of
the occupation by multiple entities of a single spatiotemporal region like a vase and an
amount of clay.
(2) To deal with engineering problems, especially the interoperability of engineering
data, YAMATO takes seriously the issues of property and attribute. It adopts the trope
theory and distinguishes between attribute and property. The former is a quality type and
the latter a tuple of a quality type and its value (qualia). YAMATO accepts two ways of
formalizing the characteristics of entities: one is the pair and the other
is the triple . Note here that, by “attribute”, we do not mean the
relation between an entity and its attribute value but the quality type which corresponds
to the dimension of entity characterization [5].
(3) YAMATO fully develops the notion of function [6][7][8] in order to deal well
with not only organisms but also artifacts [9], taking it that functions are at the heart of
artifacts. We introduce the idea of systemic function [10] to cover both biological and
artifact functions in a single framework. It strictly distinguishes behaving and function-
ing, since function is defined as a role played by a behavior in a context. In other words,
whether a behavior can perform a function or not depends entirely on in what context
5 For YAMATO’s axiomatization of is-a and instance-of relations, see Subsection 2.1. The paper on this work
is currently under review in a journal.
it is performed. For example, waving your hands is said to be functioning only in the
case where it is performed towards persons; otherwise, it is just moving your hands (not
functioning).
(4) YAMATO sharply distinguishes processes from events to capture the unfolding
process of an event which is usually left implicit [11]. An event must be dealt with as a
whole which extends in its full interval and is constituted by a process whose progress
corresponds to the unfolding process of the event. A sequence of events (e.g., a sequence
of impulses) can form a process. A process is intrinsically progressive (ongoing) and
hence it exists as a whole at any time instant after the beginning and before the ending
time points. Therefore, a process can change but an event cannot.
(5) YAMATO develops a theory of roles, taking into account the fact that the real
world is full of roles. Its unique feature is to cope well with a vacant role, namely a role
without a player. Our theory of roles claims that any part of an object has its own role
to the object as a whole which provides a context where the role is defined. YAMATO is
thus based on a principle of mutual dependence of parts and the whole. Furthermore, it
distinguishes two types of parts: a genuine part and a replaceable part. In the case of a
bike, for example, the former corresponds to the front wheel and the latter to just a wheel
that you can buy at a bike shop. This distinction plays a vital role in addressing the issue
of object modeling as is shown in Subsections 3.1 and 3.2.
(6) To deal with informational objects including conceptualization, YAMATO has a
theory of representation according to which a representation is composed of (representa-
tion) form and content. A written (realized) character is also dealt by with a representa-
tion whose form is the specification of the 2D image and the content is the corresponding
symbol. Examples of representations include an algorithm, a procedure, a plan, a com-
puter program, a piece of music, a novel, a painting, data, a symbol, a sentence, a musical
score, and a specification,
2. Elements and Organization of YAMATO
2.1. Is-a relation and Top-level Categories
Using is-a relation, YAMATO adopts single inheritance to make its taxonomic structure
clean like BFO and DOLCE. That is, the type hierarchy is made in YAMATO only when
the lower type inherits its intrinsic properties from the super types. Many of the multiple
context-dependencies are covered with the help of roles [12]. For the cases where gen-
uine multiple inheritance is necessary, Hozo prepares IS-A relation which is nothing to
do with identity problem of instances but only with property inheritance like subclass-
of relation in OWL. It may be used only when is-a relation already exists between the
two types of interest.6 The early version of YAMATO was designed under a considerable
influence of Guarino’s view on upper ontology [13].
Is-a relation in YAMATO is something more than usual property inheritance.
YAMATO formalizes instance-of and is-a relations as follows:
(A1) ∃R■Rx
(D1) Class(X) ≡de f . ∀x(x ∈ X → ∃R(■Rx ∧ X = {y|Ry}))
(D2) InstO f (x, X) ≡de f . ∃R(■Rx ∧ X = {y|Ry})
6 Hozo has a graphical interface with on-line partial consistency checking, which enables it to detect such
situations.
(D3) Xi ≡de f . {x | Class(X) ∧ InstO f (x, X)}
(D4) Is A(X, Y ) ≡de f . Class(X) ∧ Class(Y ) ∧ Xi ⊆ Yi
For every object, that object has some essen-
tial property: a property in virtue of which an
entity preserves its identity (A1). We call the
symbol ‘■’ an ‘essence operator’ and it se-
mantically means “Essentially, ...” or “It is es-
sential that ...”. An essential property of an
object determines the essential nature of that
object.
Most importantly, a class and instance-of
relation are set-theoretically defined in terms
of an essential property. A set X qualifies as
a class when and only when, for every ele-
ment x of X, x has an essential property in
common and this property satisfies the inten-
sion of X (D1); and at the same time, x bears
instance-of relation to (that is to say, x is an
instance of) X (D2). The notational definition
being used (D3), is-a relation holds between
a set X and a set Y when and only when X
and Y are classes and the set of the instances
of X is a subset of the set of the instances of
Y (D4).
Given the formalization presented above,
is-a relation implies inheritance of identity Figure 1.: Top-level categories in
criterion, so that when an instance of such a YAMATO
class loses the essential property, then it stops
being an instance of all its super classes. On the other hand, whatever happen with such
properties of an instance that are inherited through IS-A relation, no influence occurs
concerning the identity of the instance. Note that a type is not a property in YAMATO.
Therefore, human is a type and is not dealt with as a property. Instead, human type has
properties/qualities such as height, weight, and age. Figure 1 shows the top-level cate-
gories of YAMATO. At this level, YAMATO has no significant difference from other exist-
ing upper ontologie in spite of its unique treatment of quality and quantity [5].
2.2. Relevant Axioms
YAMATO is partially axiomatized:
for instance, its process/event-related Category Description
module [14] and its role-related mod- EV NT event
ule [15] have been formalized. This I N ST temporal instant
section presents part of the former for- I NT R temporal interval
malization [14]. Table 1 and Table 2 OBJ whole object
show the relevant categories and the PROC process
relations among them, respectively. ROLE role
They are also graphically shown in T IME time
Figure 2.
Table 1.: Relevant YAMATO categories [14]
Relation Description Relation Description
CC NT R causally contributes C NT X context
E NCT enacts EV NTT event spans time
EV NT K N D event-kind IntFnPRC process playing an internal role
KO N ST constitutes P part of
PC participates in PL AY play
PRE present at PROCKND process-kind
PROCT process at time ∗H asPRC has internal process
O overlap ∗PP proper part
PROD product ∗SU M sum
Table 2.: Relevant YAMATO relations [14]. Relations marked with ‘*’ are defined.
The parthood relation P
used in YAMATO has the ax-
iomatization of Closed Exten-
sional Mereology (CEM) [16].
It is binary on events and tem-
poralized, and thus ternary, on
processes and objects.
The other mereological re-
lations and operators, such as
O (O(x, y) stands for “x and
y overlap”), PP (PP(x, y) for
“x is a proper part of y”),
SU M (SU M(z, x, y) for “z is Figure 2.: Graphic representation of relevant
the sum of x and y”) and YAMATO categories and relations [14]
PROD (PROD(z, x, y) for “z is
the product of x and y”), are defined as usual in CEM [16]. When P is applied to pro-
cesses, it is written P(x, y, t) and reads “process x is part of process y at instant t.” The
temporal parameter must be a temporal instant since in YAMATO a process can be part of
another only relatively to an instant. From these constraints and the theory of processes
in YAMATO, the notion of a ‘whole process’ (a process from its beginning to its end) is
either understood as an event or is conceptually incoherent.
(A2) says that P is addictive on the category of objects OBJ (as usual, we assume
that free variables in formulas are universally quantified):
(A2) OBJ(x) ∧ OBJ(x) ∧ SU M(z, x, y) → OBJ(z) (addictivity on OBJ)
This holds as well on events (EV NT) and processes (PROC) which are also additive.
For processes, we need to introduce the binary relation ‘being present at’, written PRE,
which has as second argument a time, and is itself dissective:
(A3) EV NT(x) ∧ P(y, x) → EV NT(y) (dissectivity on EV NT)
(A4) EV NT(x) ∧ EV NT(y) ∧ SU M(z, x, y) → EV NT(z) (addictivity on EV NT)
(A5) PRE(x, t) → T I M E(t)
(A6) PRE(x, t) ∧ P(t ′, t) → PRE(x, t ′) (dissectivity on PRE)
(A7) PRE(x, t) ∧ PROC(x) ∧ P(y, x, t) → PRE(y, t) ∧ PROC(y)
(dissectivity on PROC)
(A8) PRE(x, t) ∧ PROC(x) ∧ PRE(y, t) ∧ PROC(y) ∧ SU M(z, x, y, t) → PRE(z, t) ∧
PROC(z) (addictivity on PROC)
We anticipate that P(x, y, t), with x, y processes, holds only if t is an instant, both x, y
exist at this instant t, and all the (active) participants in y are (active) participants in x.
Furthermore, the notion of enactor, which we can model logically as the sum of all the
active participants, would suffice to define P on processes.
3. Analysis of Formalizarion by YAMATO: Five Examples
This section presents how YAMATO can formalize the five cases which were given by the
organizers of the first FOUST workshop as common cases for comparing several upper
ontologies in terms of the modeling results obtained by them.
3.1. Roles
Case (1) “Mr. Potter is the teacher of class 2C at Shapism School and resigns at the
beginning of the spring break. After the spring break, Mrs. Bumblebee replaces Mr. Potter
as the teacher of 2C. Also, student Mary left the class at the beginning of the break and
a new student, John, joins in when the break ends.” GOAL: the example aims to show if
and how the ontology models the relationships between roles, players and organizations.
FOCUS: the change of roles/players; the vacancy of the teaching position; persistence
of the class while students come and go.
Simplified axioms of roles (see [15] for more details)
Context-o f (x, r) → Object(x) ∧ Role(r)
”An object x is the context of the role r.”
Role(r) → ∃x, q (Qualit y(q) ∧ Depend-on(q, x) ∧ Inhere-in(q, r) ∧ Context-o f (x, r))
”A role r has at least one quality q dependent on the context x.”
Possess(x, y, t) → Object(x) ∧ Qualit y(y) ∧ Time(t).
Hold(x, r, y, t) → ∃q (Qualit y(q) ∧ Possess(x, q, t) ∧ Object(x) ∧ Role(r) ∧ Context-
o f (y, r) ∧ Play(x, r, t) ∧ Time(t))
”An object x is playing a role r in the context y at time t, thereby becoming a role-
holder, and hence it possesses a quality q at t. x is called a player of the role r.”
Role-holder(x, t) ↔ ∃r, y Hold(x, r, y, t).
T eacher-role(r) → ∃c, s (Class(c) ∧ Inhere-in(c, r) ∧ Role(r) ∧ Context-o f (s, r) ∧
School(s))
”A teacher role has a quality c inhering in it.”
T each(x, c, t) → ∃s (Per son(x) ∧ Class(c, s))
T eacher(x, s, t) → ∃r, c (Hold(x, r, s, t)∧T eacher-role(r)∧T each(x, c, t)∧ School(s))
”A teacher holds a teacher role and temporarily possesses a quality c.”
T eacher-role(T eacher-role1 ); School(Shapism); Class(2C, Shapism); Per son(Potter);
Per son(Bumblebee)
As for Mr. Potter
Before being hired at Shapism School: Mr. Potter has no role to play.
At time t1 : Mr. Potter is hired by Shapism School and starts to play a teacher role and to
teach a class 2C, and thereby has been a teacher of Shapism School since then.
At time t2 ⩾ t1 : T eacher(Potter, Shapism, t) and T each(Potter, 2C, t),
Hold(Potter, T eacher-role1, Shapism, t) and Role-holder(Potter, t) hold.
At time t2 : Potter leaves the school and a new person Bumblebee replaces Potter.
After t2 : Potter is just a man, so only Per son(Potter) holds; that is, ¬T eacher(Potter, Shapism, t)
where t ⩾ t2 .
As for Mrs. Bumblebee
At t ⩾ t3 : T eacher(Bumblebee, Shapism, t) and T each(Bumblebee, C2, t),
Hold(Bumblebee, T eacher-role1, Shapism, t) and Role-holder(Bumblebee, t) hold.
Note that Bumblebee plays the same role instance T eacher-role1 which Potter does
until t3 . In other words, T eacher-role1 exists from t1 to t3 and exists after t3 with keep-
ing its identity even during the period when no one plays it. Either Shapism School or
Class 2C keeps its identity through the replacement. As for replaceability, Mrs. Bumble-
bee replaces Mr. Potter because T eacher-role1 is a functional part of Shapism School,
while it is not the case that John replaced Mary. This is because Student-role1 is not a
functional part of Shapism School.
3.2. Composition/Constitution
Case (2) “There is a four-legged table made of wood. Some time later (at t1), a leg of the
table is replaced. Even later (at t2), the table is demolished so it ceases to exist although
the wood is still there after the demolition.” GOAL: the example aims to show if and how
the ontology models materials, objects, and components and the relationships among
them. FOCUS: the relationship between the wood and the table and the table’s parts
over time. (Artefacts and functions are not the focus.)
The modeling of a table is fully based on the role theory discussed in Case (1). In
terms of a role theory, there is no difference between a table and a school both of which
are composed of parts that have roles in the context of the whole. Now, let the wooden
table be table1 which is composed of a top-board top-boar d1 and four legs: leg1 , leg2 ,
leg3 and leg4 . We here identify an amount of wood as well as a table and its parts. All
parts (components) used for making the table are made of wood whose total amount
shares the same spatiotemporal region with the table. There are two amounts of wood in
this case. One exists from the beginning until the exchange of a leg and the other after
the exchange and even after demolition.
Preliminary formalization
Made-o f (x, y) → (Object(x) ∧ Material(y) ∧ Constituted-by(x, y))
∃legi, rodi, top-boar d, boar d1, table1 (Leg-role(legi ) ∧ Rod(rodi ) ∧ Leg(rodi, table1, t) ∧
Boar d(boar d1 ) ∧ T opBoar d(boar d1, table1, t) ∧ T opBoar dRole(top-boar d) ∧ T able(table1 ))
↔ ComposedO f (table1, top-boar d, leg1, leg2, leg3, leg4, t) ∧ P(rodi, table1, t) ∧
P(boar d1, table1, t)
”If legi roles and their players rodi , and top-boar d and its player boar d1 are given,
then table1 is composed of those roles together with their players.”
P(x, y, t) → ∃r(Role-holder(x, t) ∧ Role(r) ∧ Context-o f (y, r) ∧ Play(x, r, t))
”If an object x is a part of y, x is playing a role r specified by the context y.”
Rod(x) ∧ T able(y) ∧ P(x, y, t) → ∃r(Role-holder(x, t) ∧ LegRole(r) ∧ Context-
o f (y, r) ∧ Play(x, r, t).
”If a rod is a part of a table, there exists a leg role which the rod is playing in the context
of the table.”
Boar d(x)∧T able(y)∧P(x, y, t) → ∃r(Role-holder(x, t)∧T opBoar dRole(r)∧Context-
o f (y, r) ∧ Play(x, r, t)
Leg(x, y, t) → Rod(x) ∧ T able(y) ∧ Time(t)
T opBoar d(x, y, t) → Boar d(x) ∧ T able(y) ∧ Time(t)
LegRole(r) → ∃c, s(LegPosition(c) ∧ Inhere-in(c, r) ∧ Role(r) ∧ T able(s) ∧ Context-
o f (s, r)
”A leg role of a table has a quality called the leg position inhering in it in the context
of the table.”
Leg(x, tbl, t) → ∃r, c, bd(Hold(x, r, tbl, t) ∧ LegPosition(c) ∧ Possess(x, c, t) ∧
LegRole(r) ∧ Play(x, r, t) ∧ T opBoar d(bd, tbl, t) ∧ P(bd, tbl, t) ∧ Support(x, bd, t))
”If an object x is a leg of a table, x is a leg-role-holder of the table by playing the leg
role, possesses the leg position of the table, and supports the top-board which is a part of
the table.”
T opBoar dRole(r) → ∃c, s(T opBoar dPosition(c) ∧ Inhere-in(c, r) ∧ Role(r) ∧
T able(s) ∧ Context-o f (s, r))
T opBoar d(x, tbl, t) → ∃r, c(Hold(x, r, tbl, t)∧T opBoar dPosition(c)∧T opBoar dRole(r)∧
Possess(x, c, t) ∧ Play(x, r, t))
During its life time, an artifact table1 can change while keeping its identity inde-
pendently of the replacement of parts unless the specification is violated. In this table
example, there are five replaceable parts such as boar d1 , rod1 , rod2 , rod3 and rod4 and
they play those five roles such as top-board role and leg1 , leg2 , leg3 and leg4 roles, re-
spectively, thereby becoming top-boar d1 , leg1 , leg2 , leg3 and leg4 role-holders which
are genuine parts of the table. Before t1 : T able1 is composed of top-boar d1 ; leg1 , leg2 ,
leg3 and leg4 . w1: Amount of wood exists which is the summation of the wooden ma-
terial used for all the replaceable parts. It shares the same spatiotemporal region with
table1 . At time t1 : A leg, say leg2 , is replaced. This means that rod2 is removed and a
new rod, say rod2−1 starts to play the leg2 role, thereby becomeing a new leg leg2 . Rod2
is no longer leg2 and it turns back to a rod as it was before it was used for leg2 . T able1
keeps its identity after this replacement. At the same time, a new amount of wooden
material, w2 (= w1 − rod2 + rod2−1 ) appears and starts to share the same spatiotempo-
ral region with table1 . At time t2 : T able1 is demolished and then it disappears, since
the specification has been violated. Assuming that no part is broken (that is, it was de-
composed), top − boar d1, leg1, leg2, leg3 and leg4 turn back to the original boar d1 ; and
rod1, rod2−1, rod3 and rod4 , respectively. W2 continues to exist.
3.3. Property Change
Case (3) “A man is walking when suddenly he starts walking faster and then breaks into
a run.” GOAL: the example aims to show if and how the ontology models change during
an event. FOCUS: the change in the speed and mode of locomotion.
As stated earlier, YAMATO distinguishes processes and events. An event is consti-
tuted by the process. Although processes can change, events cannot. Let us assume that
the change of the speed happened at t1 and the running process started at t2 . This case
consists of three occurrents such as a walking with a steady speed, another walking with
increasing speed and a running each of which is separated by a clear boundary. Since
no event can change, the second occurrent needs YAMATO’s idea of process. The man
apparently participates in a single moving occurrent which consists of a walking process
and a running process. Because the walking process exists at any time as a whole during
the process is ongoing, it can have quality, and in fact it has a speed quality. Thus the
change under consideration is naturally modeled as the change of speed attribute values
of the walking process in the same way as the color change of a flower.
Preliminary formalization
∀t in (t0, t1 ], ∃s1, s2(W al king(p1, t) ∧ Participate(John, p1, t)∧
(∀t x, t y in (t0, t1] (speed(s1, p1, t x) ∧ speed(s2, p1, t y) → s1 = s2 )))
∀t in (t1, t2 ], ∃s1, s2(W al king(p1, t) ∧ Participate(John, p1, t)∧
∀t x > t y in (t1, t2] (speed(s1, p1, t x) ∧ speed(s2, p1, t y) → s1 > s2 ))).
∀t in (t2, t3 ) (Running(p1, t) ∧ Participate(John, p1, t) ∧ speed(s, p1, t))
∀t in (t0, t3 ) (Moving(p1, t) ∧ Participate(John, p1, t) ∧ speed(s, p1, t))
W al king(p1, t) → Moving(p1, t); Running(p1, t ′) → Moving(p1, t ′)
This abstraction enables us to identify a moving process p1 which comprises a walk-
ing process at time t and a running process at time t ′. This is valid to the extent that either
is a constituent of the same (moving) event. In our theory of processes and events [11],
any event has a unique (the most abstract) and uniform process. For instance, a confer-
ence event has the conferencing process and a cooking event has the cooking process.
Imagine that John sneezes at the boundary between these two processes. In ordi-
nary situations, sneezing is not considered as a constituent of a moving event and it is
discarded in the identification of constituent processes in the moving event. In this case,
therefore, only walking and running processes are considered as constituent processes
of the moving event, and hence they can be considered as different modes of the same
moving process. This guarantees the talk of ‘change’ in the mode of locomotion. One
can go up such an abstraction hierarchy of processes as high as possible insofar as the ab-
stracted process constitutes an event. The above observation shows that the identification
of events plays a key role in our theory of occurrents (see [14] for details of axioms of
processes and events). Despite its importance, the event identification requires no special
treatment because we simply follow the conventional manner of how to identify events
such as cooking and a conference, as is implied by the following axiom:
Event(e1, per son, T) ≡de f ∃p1 ∀t in T (Per son(per son)∧Process(p1, t)∧Interval(T)∧
Participate(per son, p1, t) ∧ Constituted-by(e1, p1 ))
3.4. Event Change
Case (4) “A man is walking to the station, but before he gets there, he turns around and
goes home.” GOAL: the example aims to show if and how the ontology models change
in goal-directed activities. FOCUS: an activity/event is not completed and another ac-
tivity/event is completed instead.
We take this issue to be deeply related to the action theory. Instead of delving into
details of action-theoretic issues, however, we here mainly formalize it from the view-
point of events and processes with no much emphasis on BDI (Belief, Desire and Inten-
tion) issues. As is true of Case (3), John (the man) participates in a walking process all
times. The main issues to discuss would be (i) whether there is one event or two events
and (ii) in the case of the latter, how (on what basis) to identify the event boundary be-
tween the first and the second events. As stated already, there is only one walking process
because there is no physical break in the walking process at the time of the change of
his mind. If he stops walking, thinks for a while, turns around and starts walking back
to his home, then there are two walking processes. Insofar as processes are concerned,
the issue of terminating/beginning a process lies not in the change at the BDI level but in
the physical continuity of the walking process. As for an event, on the other hand, BDI
matters. In the case of walking event, the goal (intended destination) matters because
an event is necessarily a completion and hence requires a clear specification of how it
terminates. For example, to cross a street is an event that is constituted by (usually) a
walking process. If it fails, it is not a ‘crossing a street’ event; but it is nonetheless true
that there exists a walking process independently of the success or failure of the event.
Following the above observation, we conclude that there are two events and that
justification of the boundary identification is the change of the destination. Precisely
speaking, however, there are three events: one is planned but unsuccessful, the other two
are ad-hoc but successful. Assume that John starts to walk at t1 , turns around at t2 and
returns his home at t3 ; and that there is no time loss for the change of his mind. Let e1
be the first walking event of the interval [t1 , t2 ] and e2 be the second one of the interval
[t2 , t3 ], respectively. There is only one walking process p1 in (t1 , t3 ). Roughly speaking,
YAMATO’s notion of time is two-fold: A-series for talking about processes and B-series
for talking about events. By using A-series, YAMATO can talk about ongoing/progressive
aspects of occurrents. No event can be present because either it is already terminated,
not happened yet, or it is incomplete.7 For this reason, the following formalization does
not include even the first portion of the originally planned event, and the event change
is modeled by the fact that two consecutive events are constituted by one process, since
talk of change requires an entity to be identical throughout the changing process.8
Preliminary formalization
∀t in (t1, t2 ] constituted-by(e1, p1 ); ∀t in [t2, t3 ) constituted-by(e2, p1 );
∀t in (t1, t3 ) ∃p1 W al king(p1 )
3.5. Concept Change
CASE (5) “A marriage is a contract that is regulated by civil and social constraints.
These constraints can change but the meaning of marriage continues over time.” GOAL:
the example aims to show if and how the ontology models the evolution of the meaning of
a term. FOCUS: the continuity/discontinuity of the meaning of marriage in the presence
of changing qualifications.
A rigorous analysis of the (dis)continuity of the meaning of marriage requires that
there be three different kinds of meanings of the term that have different identity con-
ditions: the denotation of marriage; the content of marriage; and the name of marriage
according to the semiotic triangle (Peirce). Generally speaking, the denotation of a term
is the unvarying entity that is denoted by the term. The content of a term is the varying
propositional entity to which the term refers. The name of a term is the term itself that is
usually a sequence of characters.
First of all, the denotation of marriage is the entity that is denoted by the term ‘mar-
riage’: the socio-legal union between two adults that is verified by the contract between
them. Insofar as the denotation of marriage is concerned, the term ‘marriage’ refers to
the socio-legal union between two adults, regardless of time and place. Second, the con-
7 A rigorous formalization of time in YAMATO is currently under investigation.
8 To deal with the uncompleted event we need to employ explicitly the notion of plan and its execution, which
are left for future work.
tent of marriage is basically the characteristics of the denotation of marriage that are
regulated by socio-legal constraints and it varies greatly with time and place. Consider
the legalization of same-sex marriage in France in 2013. That year saw the content-level
change in French marriage: a homosexual couple has acquired the right to marry. The
key factor behind the content-level change in French marriage is the invariable denota-
tion of French marriage: the socio-legal union between two adults that meets with the
public approval of French people. Third and finally, the name of marriage is the string
‘marriage’. Notice that the name of a term is significantly different from its content, al-
though the name-level change in a term is often caused by the content-level change in the
term. It is not improbable, for example, that the legalization of same-sex marriage will
let the French government consider the employment of another name for ‘marriage’.
Intuitively understood, the socio-legal constraints that regulate marriage are strongly
influenced by the concepts of marriage that are embraced by the people in a particular
social and cultural system. This fact justifies the claim that the content of marriage is a
kind of conceptualization. Additionally, a conceptualization is considered as a kind of
representation within the YAMATO ontological framework. For YAMATO, a representation
is in nature a ‘content-bearing’ entity and a conceptualization, i.e. agents’ understanding
of (part of) the world, essentially has as content a portion of reality. See below for more
details on YAMATO’s notion of representation.
Therefore, the three types of meanings of marriage presented above are to be elu-
cidated in terms of YAMATO’s representational interpretation of conceptualization. Con-
sider a document as the example of representation which is a useful analogy for marriage.
Although the name and/or content of a document may change during its repeated revi-
sions, the first version of the document is the ‘same’ as its third version in some sense.
Likewise, by changing its name and/or content (e.g., by removing gender constraints),
marriage has a number of ‘versions’ while maintaining its ‘original’ (denotation-level)
identity. It is important to see that an analogy with a document applies to many other
entities than marriage. Consider for instance hypertension. In 1990, Japan employed as
the diagnosis criterion of hypertension the value: 160/95 mmHg, whereas in 2017, the
Japanese diagnosis criterion of hypertension is the value: 140/90 mmHg. Interpreted
from the viewpoint of a representation, the ‘1990 version’ and the ‘2017 version’ of hy-
pertension have as content 160/95 mmHg and 140/90 mmHg, respectively. At its deno-
tation level, however, hypertension refers consistently to the clinically abnormally high
blood pressure. Scientific findings are also analyzable in terms of the document analogy,
as is supported by the observation that all scientific findings are fundamentally falsifiable
hypotheses and the object (denotation) of a scientific investigation remains constant even
when a hypothesis (content) of the scientific investigation is falsified.
An overview of YAMATO’s theory of representation is as follows. A representation
is composed of a (representation) form and the content which is constituted by the rep-
resentation form. Every content is propositional. A representation can be realized more
than one time, typically in a sequence of characters (realization). A representation form
of a representation R is itself a representation whose content is uniquely denoted by the
realization of R. For instance, a musical score as a representation is composed of a se-
quence of musical notes (form) and a piece of music (content). A piece of music is the
specification which can be realized by playing actions. A musical score can be realized
on a number of papers. A sequence of musical notes is a representation whose content
is the symbols that are uniquely denoted by the musical notes, namely the realization of
the musical score.
As stated above, a conceptualization is a type of representation. The content of a
conceptualization, however, plays such a vital role in determining the essential nature
of the conceptualization that it may well be legitimate to consider a conceptualization
either as a virtually ‘formless’ representation or as a special kind of content. In summary,
concept change is to be modelled according to three types of meanings of a concept: the
denotation, the content, and the name of the concept. There are two kinds of concept
change: the content-level change and the name-level change. The content-level concept
change occurs when and only when a concept changes its content while preserving its
denotation-level identity. The name-level concept change occurs when and only when a
concept changes its name while preserving its denotation-level identity. As below a pre-
liminary formalization of concept change could be constructed from a simplified formal-
ization of YAMATO’s theory of representation.
Core formalization of representation
Representation(x) → ∃y, z, t(RepresentationForm(y)∧Content(z)∧part-o f (y, x, t)∧
part-o f (z, x, t) ∧ constituted-by(z, y, t))
”A representation is composed of a representation form and the content which is consti-
tuted by the representation form.”
RepresentationForm(x) → ∃y, t(Content(y) ∧ constituted-by(y, x, t))
”Every representation form is also a ‘content-bearing’ entity.” (RepresentationForm(x1 )∧
Content(y1 ) ∧ RepresentationForm(x2 ) ∧ Content(y2 ) ∧ constituted-by(y1, x1, t) ∧
constituted-by(y2, x2, t) ∧ y1 , y2 ) → x1 , x2
”Two representation forms are different when they constitute different contents.”
Preliminary formalization of concept change
Denotation(x) → ∃y, z, t(Name(y) ∧ Conceptualization(z) ∧ denoted-by(x, y, t) ∧
meaning-o f (z, x, t))
Conceptualization(x) → ∃y, t(Content(x) ∧ Representation(y) ∧ Time(t) ∧
part-o f (x, y, t) ∧ ∃z(RepresentationForm(z) ∧ part-o f (z, y, t) ∧
constituted-by(x, z, t)))
Name(x) → Semi Abstract(x); Conceptualization(x) → Semi Abstract(x)
Name-Time(x, y, t) → Name(x) ∧ Denotation(y) ∧ Time(t) ∧ denoted-by(y, x, t) ∧
∃z(Conceptualization(z) ∧ meaning-o f (z, y, t))
Conceptualization-Time(x, y, t) → Conceptualization(x)∧Denotation(y)∧Time(t)∧
meaning-o f (x, y, t) ∧ ∃z(Name(z) ∧ denoted-by(y, z, t))
4. Conclusion
We presented an overview of YAMATO and illustrated its theoretical and practical virtues
with a concise analysis of the five examples. Further theoretical development of YAMATO
includes its fuller axiomatization so that YAMATO will be ontologically and formally
comparable to other upper ontologies. The current axiomatization of YAMATO includes,
in particular, the axioms of is-a and instance-of relations. This work is currently under
review in a journal. In the future we plan to deepen the current formalization of YAMATO
and take the step to axiomatize the rest, e.g., regarding the categories of quality/quantity
and representation. As for its practical effectiveness, YAMATO has been extensively ap-
plied to various domains. Examples include (1) Ontology of diseases based on the River
Flow Model (RFM); (2) Development of a learning/instructional theory-aware author-
ing tool; (3) Reorganization of the grammar of English tense based on the ontology of
process and event; (4) Task ontology building of a demolition task of a nuclear power
plant; (5) Ontology building of biomimetics; and (6) Knowhow model of an expert of
ferromagnetic materials. Those applications are expected to vindicate, possibly with their
future publications, the peerless practicality of YAMATO.
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