=Paper=
{{Paper
|id=Vol-2518/paper-FOMI3
|storemode=property
|title=Characterizing IOF Terms with the DOLCE and UFO Ontologies
|pdfUrl=https://ceur-ws.org/Vol-2518/paper-FOMI3.pdf
|volume=Vol-2518
|authors=Nicola Guarino,Emilio M. Sanfilippo
|dblpUrl=https://dblp.org/rec/conf/jowo/GuarinoS19
}}
==Characterizing IOF Terms with the DOLCE and UFO Ontologies==
https://ceur-ws.org/Vol-2518/paper-FOMI3.pdf
Characterizing IOF Terms with the
DOLCE and UFO Ontologies
Nicola GUARINO a,1 , Emilio M. SANFILIPPO b,c
a ISTC-CNR Laboratory for Applied Ontology, Trento, Italy
b Le Studium Loire Valley Institute for Advanced Studies, Orléans & Tours, France
c CESR UMR 7323- University of Tours, France
Abstract. This paper is an ontological analysis exercise aiming, first of all, at clar-
ifying the intended semantic of a number of general terms used in the manufac-
turing domain, selected by the Industrial Ontologies Foundry (IOF) initiative. In
addition, we show how the DOLCE foundational ontology is well-suited as main
reference framework for this task, integrated (in a few specific cases) with more
recent work done in the framework of UFO. For each term, we propose a DOLCE-
based (first-order) axiomatization together with examples and counter-examples.
In several cases, some new primitives are introduced in addition to those used in
DOLCE.
Keywords. Manufacturing, IOF, DOLCE, UFO.
1. Introduction
It is more than thirty years that ontologies are applied for knowledge representation or
data management across engineering, e.g., in design or manufacturing [21]. The Indus-
trial Ontologies Foundry (IOF)2 has recently emerged as international effort to develop
and promote a library of reference ontologies for these domains. One of the guiding
ideas behind the IOF is that multiple data sources or information systems have a higher
chance of interoperating if based on the same ontologies and, in particular, on the same
upper-level ontology.
The work presented in the paper is an ontological analysis exercise aimed at clari-
fying the intended semantics of (some of) the most general terms identified in the scope
of the IOF. The latter have been extracted (by a IOF team) from use-cases proposed by
the IOF community to identify engineering modeling needs and, therefore, to support the
development of ontologies based on community requirements. The terms we consider
are: Plan, Manufacturing process plan, Manufacturing resource, Material resource, In-
strumental resource, Assembly, Component, Planned process, Business process, Manu-
facturing process, Assembly process, Transport process, Manufacturing machine, Equip-
1 Corresponding Author: Nicola Guarino, ISTC-CNR, Via alla Cascata 56/C, 38123 Trento, Italy; E-mail:
nicola.guarino@cnr.it (permanent address). Copyright c 2019 for this paper by its authors. Use permitted
under Creative Commons License Attribution 4.0 International (CC BY 4.0).
2 https://www.industrialontologies.org/, last accessed June 2019.
ment, Product, Product quality, Design, Feature description, Supplier, and Customer.
Others IOF terms are left out because of their unclear intended meaning at the time in
which this study is carried out.
For the purposes of the analysis we rely on the Descriptive Ontology for Linguis-
tic and Cognitive Engineering (DOLCE) [13] integrated—in a few specific cases—with
work done by the first author in the framework of the Unified Foundational Ontology
(UFO) [10], and by work done by the second author in manufacturing [20,19,18].
We will rely on the classic version of DOLCE described in the final deliverable of the
WonderWeb project [13]. Despite some of its basic choices have been slightly revisited
in further work [3], and several drastic simplifications have been proposed (e.g., [17]),
the classic version of DOLCE has remained stable since 2003. Remarkably, a proof of
consistency was published in 2011 [12]. DOLCE and OntoClean [9] have also been used
as the main inspiration to develop UFO [10].
In the following sections, the IOF informal definition is reported for each term,
followed by the proposed DOLCE-based axiomatization together with examples and
counter-examples. Some required extensions to DOLCE that are not specific to IOF terms
are discussed in the final section although only in a preliminary setting.
From a formal perspective, we rely on plain first-order logic (FOL); formulas with
free variables are meant to be universally quantified. Note also that in DOLCE most
properties and relations involving endurants are assumed to be temporally indexed. How-
ever, we will sometimes omit the temporal index for the sake of simplicity, assuming
that, if the property φ is time-indexed, φ (x) means that φ (x,t) holds ad the present time.
For ease of understanding, DOLCE predicates have been renamed using non-abbreviated
names if possible. A mapping table is reported in the appendix. The IST DOLCE taxonomy
Project 2001-33052 WonderWeb:
appears in Figure 1. Ontology Infrastructure for the Semantic Web
PT
Particular
ED PD Q AB
Endurant Perdurant Quality Abstract
PED NPED AS EV STV TQ PQ AQ … Fact Set R
Physical Non-physical Arbitrary Event Stative Temporal Physical Abstract Region
Endurant Endurant Sum Quality Quality Quality
M F POB … NPOB ACH ACC ST PRO … TL … SL … TR PR AR
Amount of Feature Physical Non-physical Achievement Accomplishment State Process Temporal Spatial Temporal Physical Abstract
Matter Object Object Location Location Region Region Region
… … … …
… T … S …
APO NAPO MOB SOB Time Space
Agentive Non-agentive Mental Object Social Object Interval Region
Physical Physical
Object Object
ASO NASO
Agentive Non-agentive
Social Object Social Object
SAG SC
Social Agent Society
Figure 2: Taxonomy of DOLCE basic categories.
Figure 1. Taxonomy of DOLCE [13]
example is that of the vase and the amount of clay: necessarily, the vase does not survive
a radical change in shape or topology, while, necessarily, the amount of clay does. There-
fore the two things must be different, yet co-located: as we shall see, we say that the vase
is constituted by an amount of clay, but it is not an amount of clay15 . Certain properties
a particular amount of clay happened to have when it was shaped by the vase-master are
considered as essential for the emergence of a new entity. In language and cognition, we
refer to this new entity as a genuine different thing: for instance, we say that a vase has a
handle, but not that a piece of clay has a handle.
A similar multiplicative attitude concerns the introduction of categories which in prin-
ciple could be reduced to others. For instance, suppose we want to explore whether or
2. Plan and Goal
2.1. Plan
IOF informal definition: A plan is a document that prescribes a collection of related
activities that achieve some organizational goal.3
We base our analysis on the notion of description. Descriptions are information entities
about things that either exist at the present time or are just desired. Plans, goals, and
designs will be considered as descriptions of a certain kind.
Let us first introduce some informal definitions:
(1) A goal is a description (more exactly, a specification4 ) of a generic desired state
(i.e., the description of a state kind). A goal may be encoded in an agent’s mem-
ory or in an information bearer like a computer file. In the latter case, the goal
may endure after the occurrence of the perdurant it describes is not desired any-
more (a goal is only historically dependent on an agent’s mind).5
(2) A plan for a certain goal is a description of a generic perdurant (a kind of DOLCE
Accomplishment)6 such that there exists an agent who believes that any perdu-
rant of such kind may cause the satisfaction of the goal.
(3) A perdurant that satisfies a plan is said to realize the plan. A plan may constrain
its realizations in various ways. For example, it may constrain the internal struc-
ture of the realizing event, its participants, etc.
Note that a plan for a certain goal may be wrong (although an agent may believe
it works). A correct plan for a goal is a plan whose realization always causes the goal
satisfaction.
Examples: A set of instructions for manufacturing a product (e.g., a car) with the desired
qualities.
Counter-examples: an arbitrary set of instructions which have no goal.
Formal account:
(A1) goalForAgent(x, y) → Spec(x) ∧ Agent(y) ∧ ∀z(sat(z, x) →
State(z) ∧ desires(y, z))
(D1) Goal(x) , ∃y(goalForAgent(x, y))
(D2) plan(x, g) , Spec(x) ∧ Goal(g) ∧ ∀y(sat(y, x) → Accompl(y)) ∧
∃w(Agent(w) ∧ ascribesGoal(w, x, g))
(D3) Plan(x) , ∃g(plan(x, g))
(D4) realizes(x, y) , Perdurant(x) ∧ Plan(y) ∧ sat(x, y)
3 IOF terms definitions are not documented in a publicly available document.
4 A specification is a description of a desired entity. See discussion in Section 8.
5 Properly speaking, a goal is something in an agent’s mind, which may be represented as a mode (a mental
attitude) inhering in the agent. The description we are talking of would be then the (propositional) content of a
goal, not a goal in itself. For our purposes, we objectify goals identifying them with their content. In this way,
instead of being specifically dependent on an agent’s mind, a goal turns out to be just historically dependent on
it. The same approach has been adopted for plans, which are identified with their descriptional content.
6 Within eventive perdurants (i.e., perdurants that are not states nor processes), DOLCE distinguishes be-
tween achievements, which are atomic, and accomplishments, which are non-atomic.
(D5) endorses(x, y) , Agent(x) ∧ Plan(y) ∧ ∃g(goalForAgent(g, x) ∧
ascribesGoal(x, y, g))
According to (A1), if an agent has a goal, then it desires any of the states described
by the goal. The sat predicate, standing for satisfies, is discussed in Section 10.1, whereas
Spec, read as ‘specification’, is presented in Section 8.1. Multiple agents may share the
same goal. According to (D5), an agent endorses a plan if one of the agent’s goals is
ascribed to the plan. Notice that an agent may endorse several alternative plans for the
same goal. Endorsing a plan does not mean intending to realize the plan.
2.2. Business Process Plan
This term is not present in the ones originally taken into account by the IOF. We believe
it is however useful as a general category for more specific classes related to engineering.
We simply define a business process plan as a plan that is endorsed by an organization;
see (D6) where Org is a primitive predicate standing for ‘organization’.
(D6) BusinessProcessPlan(x) , Plan(x) ∧ ∃y(Org(y) ∧ endorses(y, x))
2.3. Manufacturing Process Plan
IOF informal definition: A Manufacturing process plan is a specification that prescribes
the collection of related activities in a manufacturing process that produces a product
with the desired qualities.
Our informal definition is as follows:
(4) A Manufacturing Process Plan is a Business Process Plan whose goal is the
production of a Physical object with certain qualities.
Formally,
(D7) M f gProcessPlan(x) , BusinessProcessPlan(x) ∧ ∃g (plan(x, g) ∧
∀v(sat(v, g) → ∃w(beginsLi f e(v, w))))
(D8) beginsLi f e(x, y) , Perdurant(x) ∧ (PhysOb j(y) ∨ M(y)) ∧ participates(y, x) ∧
∀t(pre(x,t) → pre(y,t)) ∧ ∃z(meets(z, x) ∧ ∀t(pre(z,t) → ¬pre(y,t)))
These definitions rely on the DOLCE notions of perdurant, participation, and pres-
ence in time. According to (D7), a Manufacturing process plan is a Business plan whose
goal is satisfied by the appearance of a new physical object or amount of matter. Such
appearance is modelled by means of (D8).7 Accordingly, a perdurant x begins the life of
y iff it is such that y is constantly participating to x, and there exists a perdurant z, when
y is not present, that immediately precedes x. Intuitively, beginsLi f e models therefore
the perdurant x that is the beginning of an object’s y life, so that y is not present at those
perdurants preceding x. The definition may be strengthen by explicitly modeling specific
goal classes, e.g., for the creation or modification of technical artifacts.
7 (D8) uses Allen’s meets relation between perdurants (x meets y iff x precedes y and is temporally connected
to y).
3. Resources
3.1. Manufacturing Resource
IOF informal definition: A resource is any person or thing that adds value to a product
in its creation, production, or delivery (APICS).
We shall base our analysis on the following dictionary definition:
“The resources of an organization or person are the materials, money, and other things
that they have and can use in order to function properly” (Collins dictionary).
The fact that resources need to be actually accessible to an agent (i.e., to be under its
control) is crucial [19].8 This means the notion of resource is a relative one: something
is a resource for somebody and for a purpose. In an industrial context, we interpret the
APICS definition assuming that such purpose is the participation to a relevant value-
adding process (i.e., a Business Process). So, a first informal definition is as follows:
(5) For a given Agent, a Manufacturing Resource is an entity which is controlled
by such Agent and may participate to a Manufacturing Process owned by such
Agent.
We therefore assume that a physical object or an amount of matter is controlled by
an agent if it is in the possession of such agent, while a person is controlled by an
agent if some kind of subordination relation holds with respect to such agent. Care
is needed to account for the notion of ‘may participate’. Considering a predicate like
MayParticipate(x, y), where x is a resource and y a process, it is clear that it has an in-
tended modal meaning and y is a possible (future) process which is only meant to occur.
To get rid of modality, we model manufacturing resources in relation to plans.
Hence, something is a resource for a particular agent’s plan. Accordingly, we refine (5)
as:
(6) For a given Agent that endorses a certain Manufacturing Process Plan, a Manu-
facturing Resource for such plan is an entity that is controlled by the Agent and
satisfies the description of a participant in the plan.
Examples: a single screw present in the workshop (even as part of a product intended
to be sold); the amount of metal that constitutes such screw, assuming it may be needed
(even in melted form) in a process; a screwdriver present in the workshop;
Counter-examples: a component which is needed but is neither present in the work-
shop, nor described in the corresponding process plan; a product which is present in the
workshop (not sold yet) but cannot be used for a manufacturing process. Importantly,
entities that are not described as plan participants are not manufacturing resources. E.g.,
an amount of material stored in a company’s garage is not a manufacturing resource if it
is not associated to a process plan. Finally, time is not considered as a resource.
Terminological issues: the emphasis on value emerging from the APICS definition
seems to be restrictive. A single screw may be considered as a resource for building
an artifact, but it would be hardly considered as adding value. Moreover, we suggest
8 An accessible resource may be not available for a particular task (for example because it is allocated to
another task), so accessibility is different from availability.
to introduce a generic notion of resource, as something that may participate to non-
manufacturing processes, such as transportation processes or other business processes.
Formulas below define manufacturing resources.
(D9) m f gResource(r, x, y) , controls(x, r) ∧ M f gProcessPlan(y) ∧
endorses(x, y) ∧ ∃z(participantDescr(z, y) ∧ sat(r, z))
(D10) participantDescr(x, y) , Descr(x) ∧ Plan(y) ∧ pPartO f (x, y) ∧
∀z(sat(z, y) → ∃wt(participates(w, z,t) ∧ sat(w, x)))
(D11) M f gResource(r) , ∃xy(m f gResource(r, x, y))
Definition (D9) defines a manufacturing resource r of an agent x that endorses a plan
y as something which is controlled by x and satisfies the description of a participant in
the realization of y. In turn, a participant description is defined by (D10) as a descrip-
tion that is part of the plan and such that whatever realizes the plan has as a participant
something that satisfies such description. Altogether, these definitions convey the idea
that manufacturing resources may participate in a manufacturing process, but they do
not necessarily participate to it. In addition, it is worth stressing that according to this
view it is possible to consider an entity as a manufacturing resource only in the light of a
manufacturing process plan where the resource is (at some extent) described. This rules
out those entities that may be accidentally used during a manufacturing process, e.g.,
tools whose use was not expected by process planners. Although this perspective seems
restrictive at first glance, it makes sense in our understanding of the fact that resources
are carefully selected during planning phases according to their availability, capabilities,
or capacities, among other requirements. A proposal to be further analyzed and tested
against experts’ knowledge is to distinguish between planned and unplanned resources,
where – differently from the former – the latter can be selected on the fly depending on
specific and perhaps even unattended happenings on manufacturing shop-floors.
Finally, the definitions above rely on several notions discussed elsewhere. Endorses
holds between agents and plans (Section 2.1); sat holds between entities and their de-
scription (Section 10.1); controls is a primitive between agents and other entities.
3.2. Material Resource
IOF informal definition: A material resource is any substance from which a product
can be made. Explanation: A material substance is often referred to as raw material
in the context of a manufacturing process (IOF: Material resource. Possible synonyms:
material, input resource. Former term: material substance”)
We propose the following informal definition:
(7) A Material Resource is a Manufacturing Resource such that, if it participates to a
manufacturing process, at least parts of it are present in the intended final product
(other parts—e.g., cutoffs—may be wasted).
Examples: an amount of clay that is used during a manufacturing process to create a
vase, so that at the end of the process at least part of it constitutes the vase; a plank of
wood that is used in a process to create a table, so that at the end of the process some part
of the plank is part of the table (note that in this case the amount of wood constituting the
plank is also a material resource); a screw that is used during a manufacturing process to
create a table, so that at the end of the process the screw is part of the table.
Counter-examples: the machines, tools, fixtures, gasoline, lubricants used during man-
ufacturing processes.
Terminological comment: We are considering here those resources which are usually
listed in a bill of materials. This does not usually include the machines needed for the
manufacturing process, nor the fuels or lubricants used for their functioning, nor the
people needed to control these machines.
Let us first define the intended output of a process that realizes a manufacturing
process plan as an entity whose coming into being satisfies the goal of the plan:
(D12) intendedOut put(x, y) , ∃pgz(M f gProcessPlan(p) ∧ realizes(y, p) ∧
plan(p, g) ∧ sat(z, g) ∧ beginsLi f e(z, x))
We then define material resource as follows:
(D13) materialResource(r, x, p) , m f gResource(r, x, p) ∧
∀yt(realizes(y, p) ∧ participates(r, y,t) →
∃zst 0 (intendedOut put(z, y) ∧ partO f (s, r,t) ∧ includedIn(s, z,t 0 ) ∧ t ≺ t 0 ))
(D14) includedIn(x, y,t) , partO f (x, y,t) ∨ ∃z(const(z, y,t) ∧ partO f (x, z,t))
(D15) MaterialResource(r) , ∃xp(materialResource(r, x, p))
According to (D13), a material resource is a manufacturing resource such that, if it
participates to a manufacturing process, part of it is included in the intended result of
such process. According to (D14), an endurant is included in another endurant if it is part
of it or is part of its constituent.
3.3. Instrumental Resource
This term is not included in the original IOF terms list. The rationale for this new term is
to complete the description of the different kinds of participants in a manufacturing pro-
cess, distinguishing the process input (material resources), the process output (intended
output), and the resources needed to realize the process (instrumental resources) [19,21].
Similarly to all resources, instrumental resources are relative to a particular process
plan. For example, a certain machine could be instrumental for a manufacturing process
and just input for a maintenance process.9
(8) An Instrumental Resource is a Manufacturing Resource such that, if it partici-
pates to a Manufacturing Process, none of its parts will be included in the in-
tended output of such process.
Examples: manufacturing machines, tools, fixtures, gigs, oils, lubricants (when not used
as input of a manufacturing process);
Counter-examples: components and amounts of matter used as input of manufacturing
process.
The formal definition is analogous to that of material resource:
9 Recall that we have only defined a particular kind of input resources, namely material resources. A more
general notion of (input) resource may be useful.
(D16) instrumentalResource(r, x, p) , m f gResource(r, x, p) ∧
∀yt(realizes(y, p) ∧ participates(r, y,t) → ¬∃zst 0 (intendedOut put(z, y) ∧
∧ partO f (s, r,t) ∧ includedIn(s, z,t 0 ) ∧ t ≺ t 0 ))
(D17) InstrumentalResource(r) , ∃xp(instrumentalResource(r, x, p))
The notion of instrumental resource may be specialized to cover the distinction be-
tween resources like (i) machines or tools, (ii) fixtures or gauges, (iii) oils or lubricants,
where (i) ‘execute’ the desired task (e.g., create a hole), (ii) ‘support’ tasks execution,
and (iii) allow for the proper functioning of (i) and (ii).
4. Assemblies and Components
4.1. Assembly
IOF informal definition: An assembly is a combination of parts and components that
form a functional entity.
The IOF informal definition relies on a notion of functional unity. We believe however
that a different notion of unity is required. Consider for example a TV monitor and its
remote controller, both on the same desk, but not touching each other. How many assem-
blies are on the desk? People say two, not one. Yet, the monitor and the remote controller
form a functional entity. Our conclusion is that we should introduce a different notion
of unity, which has a topological nature, since it is based on spatial connection. Broadly
speaking, assemblies are topological wholes like all physical objects, except that they
are formed of physical objects bound together by a relation of weak spatial connection
[2]. Informally, we shall say that two physical objects are weakly connected if they are
just in touch one each other, and they maintain their own unity. On other hand, an exam-
ple of strong connection is the one existing between any two parts of a physical object
that together constitute the object itself. So, weak connection stands for contact, while
strong connection stands for intimate material connection. Typically, mechanical assem-
blies are maximally weakly-self-connected, while their basic components are maximally
strongly-self-connected.10
Such a connection may be mechanically implemented in various ways: in simple
cases we may have simple contact (e.g., a tower of wooden blocks), in other cases various
forms of mechanical joints or fastenings may be adopted. Our informal definition is
therefore as follows:
(9) An Assembly is a Technical Artifact constituted by the mereological sum of two
or more physical objects that are weakly spatially connected one each other.
This definition constrains assemblies to be technical artifacts.11 Otherwise, any pile of
stones would count as an assembly. Relying on (D12), we define technical artefacts as:
10 We shall not consider welded or glued assemblies here. They would deserve a more specific approach
since the topological unity of their components may be destroyed by the welding process.
11 The notion of technical artifact is commonly introduced to explicitly talk of functional artifacts distin-
guishing them from artifacts created, e.g., for pure aesthetic purposes like objects of art [1].
(10) A technical artifact is an entity that is/was the intended output of a manufactur-
ing process.
Note that (9) assumes that an assembly does not just coincide with a sum of weakly
connected physical objects, but rather it is constituted by such a sum. This because the
identity criterion of the assembly and that of the sum are kept separate. For example, the
assembly may survive the replacement of a component, while the sum of components
that constitutes it is a different one if a component is replaced.
Finally, (9) implicitly relies on the assumption that a physical object may keep its
nature of physical object when it is connected with another physical object. This is not
always the case: for example, when two drops of water are connected, they loose their
nature of physical objects, and a new physical object comes into being. Assuming that
the components of an assembly count as physical objects means assuming that their unity
is not destroyed by the various mechanical joints described above.
We rely here on the DOLCE notion of physical object, according to which a physical
object is a physical endurant with some kind of unity. In particular, we assume that the
unifying relation is a generalized topological connection, which can be either weak or
strong
Examples: A pile of blocks; a TV monitor; a TV remote controller; a stonewall.
Counter-examples: The sum of a TV monitor and its remote controller (assuming they
are not touching each other); a disassembled bike; a heap of stones (arranged in a casual
way).
Formally:
(D18) Assembly(x) , TechArti f act(x) ∧ ∀t(pre(x,t) → ∃wyz(dConst(w, x,t) ∧
pre(w,t) ∧ w = y + z ∧ PhysOb j(y) ∧ PhysOb j(z) ∧ wConn(y, z,t)))
(D19) TechArti f act(x) , PhysOb(x) ∧ ∃y (intendedOut put(x, y))
In the formula above, pre(x,t) and dConst(x, y,t) are DOLCE relations standing respec-
tively for presence in time and direct constitution. Definition (D18) says that an assembly
is a technical artifact such that, whenever it is present, something that directly constitutes
it is also present, and is the mereological sum of two objects that are weakly connected
one each other.
4.2. Component and Component Part
IOF informal definition: A component is a part or subassembly that goes into a higher
level assembly or the final product (adapted from APICS). Explanation: A particular
artifact can be considered as a component or an assembly depending on the context of a
manufacturing process.
To account for this notion, we first introduce a distinction between those components
that are proper parts of assemblies (which will be therefore component parts of such
assemblies) and those that simply may be parts (perhaps because they are designed to be
parts), but are not necessarily actual parts. We define the component part relation as:
(D20) componentPart(x, y) , pPartO f (x, y) ∧ PhysOb j(x) ∧ PhysOb j(y)
This reflects the idea that a component part is a special kind of part, namely a part
that can be recognized as a physical object in itself and has therefore its own unity.
Each part of a physical object which is a physical object in itself can be considered
as a component part of that object. We can now informally define the general notion
component as follows:
(11) A component is a physical object that satisfies the description of a proper com-
ponent part of an assembly within a design specification.
Formally,
(D21) Component(x) , ∃yz(DesignSpec(y) ∧ pPartO f (z, y) ∧ sat(x, z))
By looking at the definition, the DesignSpec predicate is introduced in Section 8.1
and stands for the description of a desired entity.
Example: the engine of a car (component and component part);
Counter-example: a car engine that is not installed in any car (component but not com-
ponent part); a bulb that is accidentally installed in a lamp (component part but not com-
ponent).
5. Processes
5.1. Planned Process
IOF informal definition: The term is present but not defined in the IOF list.
We define a planned process as a process that is the realization of a plan. Such a realiza-
tion is a DOLCE accomplishment, so:
(12) A Planned Process is an Accomplishment that realizes a Plan.
Example: A manufacturing process for the creation of a table;
Counter-example: John’s (unplanned) walking from location A to B.
Formally, definition (D22) relies on (D4).
(D22) PlannedProcess(x) , Accompl(x) ∧ ∃y (realizes(x, y))
5.2. Business process
IOF informal definition: A business process is a structured set of activities performed
to achieve an organizational objective.
Our informal definition is as follows:
(13) A Business process is an Accomplishment that realizes a Business Process Plan
(see (D8)).
Example: any complete realization of a business process plan.
Counter-example: a series of action which is only a partial realization of a business
process plan.
(D23) BusinessProcess(x) , Accompl(x)∧∃y (realizes(x, y)∧BusinessProcessPlan(y))
5.3. Manufacturing Process
IOF informal definition: A manufacturing process is a structured set of activities per-
formed to produce a good or service.
Our refined definition:
(14) A manufacturing process is a process that is the realization of a Manufacturing
Process Plan.
Formally,
(D24) M f gProcess(x) , Accompl(x) ∧ ∃y(realizes(x, y) ∧ M f gProcessPlan(y))
5.4. Assembly Process
IOF informal definition: An assembly process is a type of manufacturing process that
combines two or more components into a single parent assembly or final product.
Our refined definition:
(15) An assembly process is a manufacturing process whose intended output is an
assembly.
Formally:
(D25) AssemblyProcess(x) , M f gProcess(x)∧∃y(intendedOut put(y, x)∧Assembly(y))
5.5. Transport Process
IOF informal definition: A transport process is a process that involves the movement
or change in location of some raw material, component or product by some agent or
mechanism.
Our refined definition:
(16) A transport process is the realization of a plan whose goal is the change of loca-
tion of a physical object.
Formally:
(D26) TransportProcess(x) , BusinessProcess(x) ∧
∃pg(realizes(x, p) ∧ plan(p, g) ∧ ∀y(sat(y, g) → LocationChange(y)))
LocationChange is taken as a primitive for the sake of simplicity.
6. Machine and Equipment
6.1. Manufacturing Machine
IOF informal definition: A machine is a mechanical system designed expressly to per-
form a specific task, such as the forming of material or the transference and transforma-
tion of motion, force or energy (ISO 22096:2007).
The IOF definition refers to the general notion of machine adopted in mechanics, ac-
cording to which any physical object that may be used to transmit/convert/generate mo-
tion, force, or energy would count as a machine. A lever, a wheel or a pulley are exam-
ples of machines. For our purposes we simply characterize a manufacturing machine as
an assembly which may be instrumental in a manufacturing process and is therefore an
instrumental resource:
(A2) M f gMachine(x) → Assembly(x) ∧ InstrumentalResource(x)
Admittedly, this definition only weakly captures the manufacturing understanding of
machines. Future work to improve the ontological representation of machines is needed.
Examples: a drilling machine, an (assembled) bench used as support for certain opera-
tions.
Counter-examples: a lever, a pulley, an amount of fuel used in a process.
6.2. Equipment
IOF informal definition: Manufacturing equipment is equipment which is operated for
directly producing a product, in a manufacturing process (ISO 20140-1:2013).
The term ‘equipment’ in English denotes a plural entity: “the set of necessary tools,
clothing ecc. for a particular purpose” (Cambridge English Dictionary). This is clearly
different from ‘piece of equipment’.
Assuming that the IOF (and ISO) definition reported above refers to a plural entity,
the emphasis on directly producing a product deserves attention. Is, e.g., a forklift used to
move materials around in the factory or to the production line an equipment? The forklift
is not directly producing the product but is certainly indirectly necessary to supply heavy
materials to the production line.
Our informal definition is therefore as follows:
(17) An equipment is a maximal collection of manufacturing resources that may be
allocated to a manufacturing process.
If this informal definition is accepted, some further work is done to formally charac-
terize it. The idea is that, if several duplicates of a certain resource are available, only one
of them may be allocated to a certain process, becoming therefore a piece of equipment
for such process.
7. Product and Product Qualities
7.1. Product
IOF informal definition: A product is the tangible outcome of a process (ISO 6707-
3:2017). A product is often produced for sale, barter, or internal use, etc.
The IOF informal definition underlines two aspects of a product: its economic relevance
and the fact that it is the outcome of a process. To better clarify the former, we think it is
useful to first clarify the notion of good:
(18) A good is a (tangible or intangible) object that has an economic value, over which
ownership rights can be established and whose ownership can be transferred from
one agent to another.
Note that, according to [11], the possibility of transferring their ownership is what dis-
tinguishes goods from services: goods are transactable and transferrable, while services
are transactable but not transferrable (the purpose of the transaction is not a transfer of
ownership).
Not all goods are products, however. In particular, real estates are not usually con-
sidered as products. A well-founded account of the notions of good, service, and product
(including financial products) requires therefore some further work. For our purposes,
we focus on manufacturing products, suggesting the following informal definition:
(19) A manufacturing product is an amount or matter or a physical object that is/was
intended to be sold, and is the intended output of a manufacturing process.
Examples: a car; some sieved gravel; some crude oil extracted from sea; some sawdust
properly collected in order to be sold.
Counter-examples: a tool produced by a company for internal purposes and not intended
to be sold. Some sparse sawdust not intended to be sold.
Formally, we define a manufacturing product as follows:
(D27) M f gProduct(x) , ∃yp (intendedOut put(x, y) ∧ Plan(p) ∧
∀z(realizes(z, p) → Selling(z) ∧ theme(x, z)))
By the definition above, a product is the intended output of a manufacturing process
such that there exists a plan of selling it. We rely here on a Selling primitive, which
classifies those events that are selling actions, and a thematic role12 relation, which says
that x is the theme of such actions.
7.2. Product Quality
IOF informal definition: A physical or functional characteristic of a product that can be
measured or qualitatively evaluated. (Source: Adopted principly from ISO 9000:2016)
The above definition is in line with the DOLCE notion of individual quality. Individual
qualities (qualities for short) may be seen as specific aspects of things we use to com-
pare them. They inhere in things, where inherence is a special kind of existential depen-
dence relation, which is irreflexive, asymmetric, anti-transitive, and functional. They are
directly comparable, while objects and perdurants can be compared only with respect to
a certain quality kind (e.g., to compare physical objects, one resorts to the comparison
of their shapes, sizes, weights, and so on). Qualities are distinct from their values (a.k.a.
qualia), which are abstract entities representing what exactly resembling qualities have
in common, and are organized in spaces called quality spaces; each quality kind has its
own quality space. For instance, weight is a quality kind, whose qualia form a linear
quality space. Note that DOLCE qualities are directly comparable but not necessarily
12 Thematic roles are ways of participating to an event, typically corresponding to the semantic arguments of
a verb.
measurable: for instance, it may make sense to say that a product is more beautiful or
more reliable than another even without having a metric for beauty or reliability.
Based on this notion, we define product qualities as follows:
(20) A product quality is a specific aspect of a product which can be directly compared
with similar aspects of another product.
Examples: The mass of a car, the shape of a bolt.
Counter-examples: The head of a bolt, the surface of a table, the specific redness of an
apple (they are dependent entities like qualities, but they are not qualities).
Formally,
(D28) ProdQuality(x) , Quality(x) ∧ ∃y (M f gProduct(y) ∧ inheres(x, y))
Finally, note that the IOF definition of product quality covers functionalities, too. The
latter have been extensively discussed in the literature and different ontologies have been
proposed (e.g., [5,15]). The representation of functionalities in our framework is left to
future work; the reader can refer to [4] for a DOLCE-based approach to model function-
alities as qualities.
8. Design and Feature Specification
8.1. Design Specification
IOF informal definition: A design is a specification that describes a collection of fea-
tures to be created for a product.
Let us compare the above definition with those of the following IOF terms:
• Feature description: a description that details some distinctive characteristic about
a product.
• Quality specification: a specification of some feature, input, processing, or output
expected in a new product, a system, or satisfying some other organizational need,
but without expressing the alternatives, technical details or how the requirment is
to be met.
First, the three terms seem to be strictly related. Second, they leave space for ambigui-
ties. E.g., ‘design’ explicitly talks of ‘features’, but nothing is said on the intended mean-
ing of the latter term, which is notoriously ambiguous [20]. On the other hand, ‘feature
description’ refers to products’ characteristics, but it is unclear how design and feature
descriptions relate to each other. For example, is ‘characteristic’ more general than ‘fea-
ture’? Finally, ‘quality specification’ is meant to provide – at a first glance – a generic
description of the desired product without specifying any technical details.
For our axiomatization, we first extend the notion of Description (cf. Section 10.1)
to explicitly cover specifications and then define design specifications as the most en-
compassing descriptions for a desired artifact:
(21) A specification is a description of a desired entity. It is historically dependent on
the existence of an agent who desires the entity that the description describes.
(22) A design specification is the specification of a desired artifact. It specifies its
qualities, features, components (including the assembly relations between them)
functionalities, materials, etc.
Examples: a design specification describing a table (to be realized) made of wood and
consisting of various components (legs, screws, etc.) assembled in a specific way.
Counter-examples: a process plan, a feature specification.
Formally:
(D29) Spec(x) , Descr(x) ∧ ∃a(Agent(a) ∧ ∀y(sat(y, x) → desires(a, y)))
We can now characterize design specifications as follows:
(D30) DesignSpec(x) , Spec(x) ∧ ∀y(sat(y, x) → TechArti f act(y))
For the definition of technical artefacts (TechArti f act), see Section 4.
8.2. Feature Specification
IOF informal definition: A feature description is a description that details some distinc-
tive characteristic about a product.
In this definition, it is unclear what ‘characteristics’ are. In the analysis of this term done
within the scope of BFO, the term ‘feature description’ is said to be “ an umbrella term
including quality, product quality of material entities or information entities, metalevel
characteristics such as availability, reliability, average dimensions, and so forth of se-
ries or batches of material entities, as well as characteristics of processes such as rate,
continuity and so forth”.
In the light of the above considerations on specifications, we think that the term ‘fea-
ture specification’ is more appropriate. The following informal definition is proposed:
(23) A Feature Specification is a Specification that describes desired Qualities or
(physical) Features. The latter are elements such as holes and protrusions, which
are ontologically dependent physical objects.
Example: hole specification, protrusion specification, bump specification, specification
of product’s weight or height.
Counter-example: specification of product’s component, plan.
Formally,
(D31) FeatureSpec(x) , Spec(x) ∧ ∀y(sat(y, x) → Feature(y) ∨ Quality(y))
Specific axioms for feature modeling can be introduced when needed (e.g., to specify
that material features, differently from immaterial ones, are proper parts of their material
hosts [18]).
9. Suppliers and Customers
9.1. Supplier
IOF informal definition: A provider of goods or services. Source: APICS (Revised: An
organization or individual that sells or provides products or services to other organiza-
tions and individuals.)
We suggest to interpret the IOF definition in terms of the notion of commitment:
(24) A supplier is an agent who is publicly committed to sell some products or ser-
vices.13
Example: A company that sells cars.
Counter-example: A private person who occasionally agrees selling his car.
The same approach can be in turn used to define customers.
9.2. Customer
IOF informal definition: A organization or person that buys or receives a good or ser-
vice.
In our approach, customer is defined as follows:
(25) A customer is an agent who is publicly committed to buy some products or ser-
vices.
Example: John buying a car.
Counter-example: John renting a car.
In DOLCE, commitments would be classified as mental objects existentially dependent
on an agent. We prefer however to model commitments and other mental attitudes adopt-
ing the UFO approach [10], according to which mental attitudes are externally dependent
modes, which inhere in agents and are existentially dependent on other things. We see
UFO modes as a generalization of DOLCE qualities that, besides individual qualities,
allow for relational qualities, which are qualities that, besides inhering in a certain entity,
are existentially dependent on something else. For example, the love John has towards
Mary is a relational quality inhering in John and existentially dependent on Mary.
This generalized account of qualities is crucial to model reified relationships, a.k.a.
relators [6,7], which are mereological sums of qualities. In particular, to account for sup-
pliers and customers we have to account for a contractual relationship, which regulates
an economic exchange perdurant. As shown in Fig. 2, such a relationship is a sum of
mutually dependent conditional commitments inhering in the provider and the receiver.
In turn, commitments are externally dependent modes of a special kind, which cease to
exist when an event that fulfills them occurs. So, in Fig. 2, a provider’s commitment to
sell is a mode inhering in the provider and existentially dependent on a reciprocal com-
13 We suggest to reserve supplier for selling goods, and provider for selling services. Another possibility is
to adopt the terms good supplier and service supplier.
mitment to buy inhering in the receiver. The former commitment is fulfilled by a sell
perdurant, the latter commitment is fulfilled by a buy (cash) perdurant.
In the light of this analysis, we can define a supplier as an agent who has a commit-
ment to sell, and a customer as an agent who has a commitment to buy.
(D32) Supplier(x) , Agent(x) ∧ ∃c(Commitment(c) ∧ inheres(c, x) ∧
∀y( f ul f ills(y, c) → Selling(y)))
(D33) Customer(x) , Agent(x) ∧ ∃c(Commitment(c) ∧ inheres(c, x) ∧
∀y( f ul f ills(y, c) → Buying(y)))
The definitions rely on the primitive relation fulfills (holding between a perdurant
and a commitment), as well as on the Selling and Buying primitives. The formulas may be
adjusted in order to characterize the commitments as public commitments (e.g., towards
a target community of potential customers) or to specify the nature of the things sold.
We could also define a prospective customer as a person to whom a specific offer-
ing is addressed but may decide not to buy. In this case we would need to model the
customer’s claims towards the supplier [16].
10. Required Extensions and Adjustments to DOLCE
10.1. Descriptions and their Satisfaction
Descriptions are endurants that are not directly located in space and depend on a com-
munity of intentional agents. They are hereby understood as information content entities,
e.g., the informative content of a business plan that is supported in multiple information
carriers like digital files or printed materials. 14
(A3) Descr(x) → NonAgentiveSocialOb ject(x)
(A4) Descr(x) ∧ partO f (y, x) → Descr(y)
(A5) sat(x, y,t) → (PhysicalEndurant(x) ∨ Quality(x)) ∧ Descr(y) ∧
TimeInterval(t)
(A6) sat(x, y) → Perdurant(x) ∧ Descr(y)
The sat predicate models the compliance between a description and the ‘realizing’ entity;
e.g., a technical artefact and a design specification. Two versions of this predicate are
used, depending on the nature of the first argument: if it is an endurant or a quality, then
a temporal index is introduced to capture the time at which compliance holds; e.g., a
certain product may satisfy a given description at a time t but not at t 0 .
10.2. Physical Objects and Topological Connection
Physical objects are generically assumed in DOLCE as physical endurants with unity,
but their exact kind of unity is not specified. For our purposes, we understand a phys-
ical object as a maximally self-connected amount of matter of a certain kind, or as a
14 See [14] for the introduction of descriptions in the DOLCE framework. With respect to such paper, we
assume here that a description describes just one concept, so that satisfying a description means being classified
by the corresponding concept.
Figure 2. OntoUML modeling pattern for economic contracts [8]
connected sum of maximally connected amounts of matter of different kinds. So, a drop
of water in a glass is a physical object, but if more water is poured the water originally
constituting the drop does not constitute a physical object any more. A minimal formal-
ization of connection is reported below. See [2] for an analysis of the difference between
weak and strong connection.
(D34) spatiallyConnected(x, y) ,
∃l1 l2 (spatialLocation(l1 , x) ∧ spatialLocation(l2 , y) ∧ connected(l1 , l2 ))
(A7) connected(x, x)
(A8) connected(x, y) → connected(y, x)
11. Conclusion
We discussed across the paper how the DOLCE foundational ontology, used in tandem
with UFO, can support knowledge representation for engineering and, in particular, for
manufacturing modeling. Although the analysis aimed at discussing terms relevant in
the context of the IOF, these capture general and basic notions. Hence, the value of the
analysis is not restricted to the IOF and is applicable in manufacturing taken at large.
Providing a rigorous ontological framework for manufacturing proved challenging
and, not surprisingly, further work is necessary. E.g., we implicitly relied on a number of
notions belonging to the realm of social ontology such as agent or organization, as well
as the idea that agents control resources or endorse plans to realize their goals. Further
work is required to enhance the formal representation of these notions in a way that is
functional for manufacturing modeling. Concerning the representation of resources, it
may be useful to distinguish and characterize different resource classes depending on
their role with respect to processes. Also, one should better characterize formal relations
to explicitly capture the availability of resources or their allocation to perdurants.
Finally, recall that DOLCE (and UFO) is a foundational ontology, whose extension
and application to manufacturing can be done in a number of different ways according
to experts’ and stakeholders’ requirements. The material presented throughout the paper
does not therefore show the way in which DOLCE has to be used for manufacturing.
It rather shows a possible manner of extending it based on previous works and discus-
sions with domain experts. Our exercise shows that the ontology is well suited for man-
ufacturing representation. E.g., by means of the relation of constitution we can sharply
distinguish between products and the materials out of which they are made, but also an
assembly from its components. The first distinction is useful to classify materials and
make sense of engineering parlance according to which a product is made of a certain
material. In the second case, we can claim that (at least some of) the components forming
an assembled product can be replaced without compromising the product’s identity.
Concluding, we see on the one hand a growing interest in the manufacturing com-
munity (at both academia and industry) towards the use of ontologies. On the other
hand, however, there is also a tendency towards representational approaches either based
on poor modeling principles which only superficially capture the complexity of do-
main knowledge, or which attempt to reduce multiple viewpoints to a single prescribing
model. Against the former tendency, domain experts and stakeholders should be aware
that ontology development is as complex as any other engineering task. The better the
ontology is, the higher are the chances of re-using it across systems for data organiza-
tion, data sharing, or automated reasoning. The conceptual nuances of ontologies aim at
making explicit the complexity of domain knowledge; they are not there for ontologists’
riddles. Against the latter tendency, monolithic reference systems have probably better
performances rather than pluralistic systems for practices like homogeneous data man-
agement. We hold, however, that ontologies must represent human knowledge by tak-
ing into account the commonalities and differences of multiple application contexts and
knowledge systems. When these systems do not share the same view, forcing them to fit
the same representational model is a high questionable choice.
Acknowledgments: We thank the chairs of FOMI 2019 for the possibility of submitting
this document in its entirety. We also wish to thank the IOF members for the discussions
led to this work, and the anonymous reviewers of the paper for their useful comments.
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Appendix: DOLCE Predicates Abbreviations Table
Signature hereby used DOLCE predicate Informal reading
const K constitution
dConst DK direct constitution
inheres qt inherence
participates PC participation
partOf P part
pPartOf PP proper part
pre PRE presence in time
Accompl ACC accomplishment
Agent APO or ASO agent
Feature F feature
M M amount of matter
NonAgentiveSocialObject NASO non-agentive social object
Perdurant PD perdurant
PhysicalEndurant PED physical endurant
PhysObject POB physical object
Process PRO process
Quality Q quality
State ST state
TimeInterval T time interval