Foundational ontologies provide the basic concepts upon which any domain-specific ontology is built. This paper presents a new foundational ontology, UFO, and shows how it can be used as a guideline in business modeling and for evaluating business modeling methods. UFO is derived from a synthesis of two other foundational ontologies, GFO/GOL and OntoClean/DOLCE. While their main areas of application are natural sciences and linguistics/cognitive engineering, respectively, the main purpose of UFO is to provide a foundation for conceptual modeling, including business modeling.
A foundational ontology, sometimes also called ‘upper level ontology’, defines a
range of top-level domain-independent ontological categories, which form a general
foundation for more elaborated domain-specific ontologies. A well-known example of
a foundational ontology is the Bunge-Wand-Weber (BWW) ontology proposed by
Wand and Weber in a series of articles
As has been shown in a large number of recent works
A unified foundational ontology represents a synthesis of a selection of
foundational ontologies. Our main goal in making such a synthesis is to obtain a
foundational ontology that is tailored towards applications in conceptual modeling.
For this purpose we have to capture the ontological categories underlying natural
language and human cognition, which are also reflected in conceptual modelling
languages such as ER diagrams or UML class diagrams. In
For UFO 0.1, the first experimental version of our Unified Foundational
Ontology (UFO), we combine the following two ontologies: (1) the General Formal
Ontology (GFO), which is underlying the General Ontological Language (GOL)
developed by the OntoMed research group at the University of Leipzig, Germany; see
www.ontomed.de and
Our choice is based on personal familiarity and preferences and not on an
evaluation of all alternatives. Nonetheless, in previous attempts, GFO has been proven
insightful in providing a principled foundation for analyzing and extending conceptual
modeling and ontology representation languages and constructs
We have obtained our synthesis by: (i) selecting categories from the union of
both category sets; (ii) renaming certain terms in order to create a more ‘natural’
language; (iii) and adding some additional categories based on relevance for
conceptual modeling according to our experience. We also make references to BWW,
the Web ontology language OWL, the Unified Modeling Language (UML), the
terminology standard ISO1087-1:2000
We present UFO 0.1 both as a MOF/UML model and as a vocabulary in
structured English, similar to the BSBR Structured English of
UFO is divided into three incrementally layered compliance sets: (1) UFO-A defines the core of UFO, excluding terms related to perdurants and terms related to the spheres of intentional and social things; (2) UFO-B defines, as an increment to UFOA, terms related to perdurants; (3) UFO-C defines, as an increment to UFO-B, terms related to the spheres of intentional and social things, including linguistic things. This division reflects a certain stratification of our “world”. It also reflects different degrees of scientific consensus: there is more consensus about the ontology of endurants than about the ontology of perdurants, and there is more consensus about the ontology of perdurants than about the ontology of intentional and social things.
We hope that this division into different compliance sets will facilitate both the further evolution of UFO and the adoption of UFO in business modeling and ontology engineering. In section 2 we present UFO-A 0.1, while UFO-B 0.1 and UFO-C 0.1 are presented in the sections 3 and 4, respectively. Section 5 illustrates how UFO can be used to evaluate some business modeling methods. Section 6 concludes the article.
We first present the upper part of UFO 0.1 as a MOF/UML model in Figure 1. Notice the fundamental distinction made between sets and entities as things that are not sets (called ‘urelements’ in GFO).
In structured English, the upper part of UFO 0.1 can be introduced as follows. thing : anything perceivable or conceivable [ISO:object]. Corresponding terms:
GFO:entity; DOLCE:entity, owl:Thing; BSBR:thing set : thing that has other things as members (in the sense of set theory) thing is member of set : designated relationship that is irreflexive, asymmetric and intransitive member : role name that refers to the first argument of the thing is member of set relationship type set is subset of set : designated relationship that is reflexive, asymmetric and transitive. Constraint: For all t:thing; s1, s2 : set – if t is member of s1 and s1 is subset of s2, then t is member of s2 entity : thing that is not a set; neither the set-theoretic membership relation nor the subset relation can unfold the internal structure of an entity [GFO:urelement] type : entity that has an extension (being a set of entitys that are instances of it) and an intension, which includes an applicability criterion for determining if an entity is an instance of it; and which is captured by means of an axiomatic specification, i.e., a set of axioms that may involve a number of other types representing its essential features. A type is a space-time independent pattern of features, which can be realized in a number of different individuals. [based on GFO:universal]. Corresponding terms: UML:class; DOLCE:universal; owl:Class; BSBR:”generic thing” entity is instance of type : designated relationship (called classification) instance : role name that refers to the first argument of the entity is instance of type relationship type set is extension of type : designated relationship. Constraint: For all o:entity, t:type, s:set – if o is instance of t and s is extension of t, then o is member of s. extension : role name that refers to the first argument of the set is extension of type relationship type type is subtype of type : designated relationship that is irreflexive, asymmetric and transitive (also called generalization). Constraint: For all t1, t2 : type; s1, s2 : set – if t1 is subtype of t2 and s1 is extension of t1 and s2 is extension of t2, then s1 is subset of s2. subtype : role name that refers to the first argument of the type is subtype of type relationship type individual : entity that is not a type. The relation between individual and type is one of classification. Corresponding terms: GFO:individual; DOLCE:particular thing is part of individual : designated relationship that is reflexive, asymmetric and transitive (also called aggregation relationship). part : role name that refers to the first argument of the thing is part of individual relationship type type is categorization type of type : designated relationship where the first argument/role is a higher-order type whose instances form a subtype partition of the second argument (also called categorization relationship). Examples: BiologicalSpecies is categorization type of Animal; PassengerAircraftType is categorization type of PassengerAircraft. Constraint: For all t1, t2, t3: type – if t3 is categorization type of t1 and t2 is instance of t3, then t2 is subtype of t1 categorization type : role name that refers to the first argument of the type is categorization type of type relationship type. Corresponding names: GFO:higherorder universal; BSBR:”categorization scheme”; UML:powertype type is categorized by type : designated relationship that is the inverse of type is categorization type of type. Corresponding relationship type expressions: BSBR:”type has categorization-scheme” *
Individual
Entity {disjoint, complete}
*
Part Instance 1..*
* Subtype
Thing *
Member
Subset 1..*
Based on
In structured English, the different kinds of types are defined as follows. relationship type : type whose instances are relationships sortal type : type that carries a criterion for determining the individuation, persistence and identity of its instances. An identity criterion supports the judgment whether two instances are the same. Every instance in a conceptual model must have an identity and, hence, must be an instance of sortal type. base type : sortal type that is rigid (all its instances are necessarily its instances) and that supplies an identity criterion for its instances [OntoClean:type].
Examples: Mountain; Person. Corresponding terms: BWW:”natural kind” phase type : sortal type that is anti-rigid (its instances could also not be instances of it without loosing their identity) and that is an element of a subtype partition of a base type [OntoClean:”phased sortal”]. Examples: Town and Metropolis are phase subtypes of City; Baby, Teenager and Adult are phase subtypes of Person role type : sortal type that is anti-rigid and for which there is a relationship type such that it is the subtype of a base type formed by all instances participating in the relationship type [OntoClean:role]. Examples: DestinationCity as role subtype of City; Student as role subtype of Person Role and phase types cannot supply an identity criterion for its instances. For this reason, roles and phases must be subsumed by a base type from which an identity criterion is inherited. mixin type : type that is not a sortal type and can be partitioned into disjoint subtypes which are sortal types (typically role types) with different identity criteria. Since a mixin is a non-sortal it cannot have direct instances [OntoClean:non-sortal]. Examples: Object; Part; Customer; Product
Entity
Type
The theory of types which is part of UFO-A provides a foundation for a number
of modeling primitives that, albeit often used, are commonly defined in an ad hoc
manner in the practice of conceptual modeling (e.g. kind, phase or state, role, mixin).
In particular, this theory can be considered as an elaboration in the way types are
accounted for in the BWW approach. In one of the BWW papers
We distinguish between a number of different kinds of individuals, as shown in Figure 3.
Perdurant Amount of
Matter {disjoint, complete}
Physical Object
Individual substance individual : endurant that consists of matter (i.e., is `tangible’ or concrete), possesses spatio-temporal properties and can exist by itself; that is, it does not existentially depend on other endurants, except possibly on some of its parts) [based on GFO:substance]. Corresponding terms: BWW:thing moment individual : endurant that cannot exist by itself; that is, it depends on other endurants, which are not among its parts [based on GFO:moment] endurant bears moment individual :
GFO:”substance bears moment”]
designated relationship [based on
physical object : substance individual that satisfies a condition of unity and for
which certain parts can change without affecting its identity
amount of matter : substance individual that does not satisfy a condition of unity;
typically referred to by means of mass nouns. Amounts of matter are, in general,
mereologically invariant, i.e., they cannot change any of their parts without
changing their identity [DOLCE]. Examples: water; gold; wood; milk; sand
intrinsic moment : moment individual that is existentially dependent on one single
individual
intrinsic moment inheres in endurant : designated relationship [GFO]
quality : intrinsic moment that inheres in exactly one endurant and can be mapped to
a value (quale) in a quality dimension
of UFO-A 0.1 to
Most business information systems include a ‘business object class’ Customer for
representing the customers of the business. In figure 4-a, the role type Customer is
defined as a supertype of Person and Corporation. This model is deemed
ontologically incorrect for two reasons: first, not all persons are customers, i.e. it is
not the case that the extension of Person is necessarily included in the extension of
Customer. Moreover, an instance of Person is not necessarily (in the modal sense) a
Customer. Both arguments are also valid for Organization. In a series of papers
Customer «mixinty pe»
Customer «basety pe»
Person «basety pe» Corporation Person
Corporation
«rolety pe» PersonalCustomer
«rolety pe» CorporateCustomer
In this example, Customer has in its extension individuals that that obey different identity criteria, i.e., it is not the case that there is a single identity criteria which applies both for Persons and Corporations. Customer is hence a mixin type (a nonsortal) and, by definition, cannot supply an identity criterion for its instances. Since every instance in the model must have an identity, thus, every instance of Customer must be an instance of one of its subtypes (forming a partition) that carries an identity criterion. For example, we can define the sortals PrivateCustomer and CorporateCustomer as subtypes of Customer (fig.4-b). These sortals, in turn, carry the (incompatible) identity criteria supplied by the base types Person and Corporation, respectively.
In many business information systems, both individual products and product types
have to be represented. In a prototypical case, the product individual type, whose
instances are identified with the help of serial numbers, is categorized by the
corresponding product model type, which is a 2nd order categorization type, whose
instances are subtypes of the product individual type. Figure 6 shows this situation for
1 This problem is also mentioned in
Color
Car
«isClassif iedBy » * 1 «classif icationty pe»
CarModel BMW Z3
VW Passat
«instance» «instance»
4711 : Car
Color =black
A complete treatment of an ontology of perdurants requires a detailed discussion on
an ontology of temporal entities (chornoids)
An event is related to the states before and after it has happened. atomic event : event that happens instantaneously, i.e. an event without duration.
[based on BWW:event and GFO:change] complex event : event that is composed of two or more events. Examples: a football game, a conversation, a race, a birthday party, a business process. state is pre-state of event : designated relationship state is post-state of event : designated relationship
Perdurant (from UFO-A) State 1
PreState 1 PostState * Atomic Event
Event *
2..* Complex
Event
The ‘objective’ perdurant categories (atomic and complex) event and state defined in
UFO-B are essential concepts for process modeling, but they are not sufficient for
business process modeling, where intentional and social concepts such as action,
activity, and communication are needed. The following account of intentional and
social things is at an early stage of development and therefore rather incomplete.
Nevertheless, we think that it gives an impression of the range of ontological
categories that is needed to explain business process modeling.
physical agent : physical object that creates action events affecting other physical
objects, that perceives events, possibly created by other physical agents, and to
which we can ascribe a mental state. Examples: a dog; a human; a robot
action event : event that is created through the action of a physical agent
non-action event : event that is not created through an action of a physical agent
physical agent creates action event: designated relationship
physical agent perceives event: designated relationship
non-agentive object : physical object that is not a physical agent. Examples: a chair;
a mountain
mental moment : intrinsic moment that is existentially dependent on a particular
agent, being an inseparable part of its mental state. Examples: a thought; a
perception; a belief; a desire; an individual goal. Constraint: For all mm : mental
moment; e:endurant — if mm inheres in e then e is physical agent.
communicating physical agent : physical agent that communicates with other
communicating physical agents. Examples: a dog; a human; a
communicationenabled robot
institutional agent : institutional fact
In the following subsections we briefly present some preliminary results in order to exemplify how UFO can be used to evaluate some business modeling methods.
The Enterprise Ontology, which was developed in a project led by the AI Applications Institute at the University of Edinburgh (see Uschold, King, Moralee & Zorgios, 1998). Based on a simple upper-level ontology (‘meta-ontology’) consisting of the three modeling concepts entity, relationship and actor, it provides definitions for nearly 100 terms, both in natural language and in the formalism of Ontolingua.
For simplicity, the distinction between an entity (individual) and an entity type is avoided. An agent (called actor) is defined as a special entitiy that can play an actor role in certain relationships (such as in performs Activity, has Capability, etc.).
There is no independent concept of an event in the Enterprise Ontology: events are defined as ‘a kind of activity’. Remarkably, the authors consider also events that take place as a result of natural necessity (such as ‘water flowing down a hill’) as activities of ‘inanimate actors’ (such as gravity).
The following points highlight some shortcomings of the Enterprise Ontology: (i) For conceptual modeling, it is essential to distinguish between individuals and types; (ii) It seems to be questionable to view natural forces that cause certain events to happen, such as gravity, as actors/agents; in UFO 0.1 agents have a mental state and are able to act (create action events), perceive and possibly to communicate; (iii) Events should not be subsumed under activities. Rather, they should be first-class citizens of the metamodel.
In
The REA framework, whose ontological foundations are defined in
Despite of considering both individual and types, the authors do not elaborate on the different sorts of types which are necessary for conceptual enterprise modeling (see section 2.4.1).
An example of lack of ontological clarity is found when the authors mix the notions of event and commitments. For instance, figure 5, commitment and economic event are collapsed in one single type-image. Additionally, the relationships partner and reserves (defined to hold between agent/commitment and resource/commitment, respectively) are considered as subtypes of participation and stock-flow (defined between agent/economic event and resource/economic event). In our framework, whilst an economic event is a type of complex action, a commitment is a type of relational moment. Examples of other types of social moments (a subtype of relational moment) defined in REA include accountability, responsibility, assignment, and custody.
Despite recognizing the importance of part-whole relations in the enterprise
domain (for example to model the relation between a resource and its parts), the
treatment offered is insufficient. The authors only briefly mention a relation of
composition that, together with other relations such as substitutes (meaning that a
resource can substitute another), is subsumed under the relation of linkage between
resources. No axiomatization for composition is provided. In a companion paper
The unified foundational ontology UFO 0.1 presented in this paper should be viewed as an attempt to assemble a foundational ontology for conceptual modeling on the basis of other, already well-established and philosophically justified foundational ontologies. We have stratified UFO into three ontological layers in order to distinguish its core, UFO-A, from the perdurant extension layer UFO-B and from the agent extension layer UFO-C. Although there is not much consensus yet in the literature regarding the ontology of agents, such an ontology is needed for building the foundation of conceptual business process modeling. UFO-C 0.1 is a first attempt to construct these foundations. We hope that we can validate and further improve it by investigating its applicability to business modeling problems.