Draft document

Introduction

BFO is a formal ontology, which means that it is designed to be neutral with regard to the material domains to which it is applied. The application of a formal ontology such as BFO brings benefits of reuse, cumulation of data, and reasoning, and provides a set of common formal theories (for example of mereotopology [] and of qualitative spatial reasoning []) which do not need to be redeveloped for each successive domain. For such benefits to be achievable, however, BFO must be capable of being applied to material domains and in what follows we document how such application is to be effected. We describe the conditions which must be satisfied by entities of given sorts if they are properly to be categorized as instantiating the different universals recognized by BFO and we provide a summary of the associated relations.

To specify these conditions we will utilize a semi-formalized English that has approximately the expressivity of first-order logic (FOL) with identity. In a future document we will provide a formalized treatment of these specifications using FOL; a parallel effort is also underway using OWL.

1. Entity

Elucidation: An entity is anything that exists.

Axiom: Entities may be either particular or also universal. [, ]

In this document we concentrate primarily on entities which are particulars and on the relations between particulars elsewhere called ‘instance-level relations’ []. That is, the categories discussed below are in every case categories of particulars (their extensions are groups or collections of particulars in reality). Because BFO is the ontology that forms the basis of the Information Artifact Ontology and universals are included among the targets of the IAO: about relation, BFO must include universals within its domain of discourse.

We use ‘universal’ and ‘type’ as synonyms, and employ ‘category’ to refer to the higher-level universals to which BFO terms refer. These and related technical terms of ontology are elucidated further in [, 1, ].

Attributive classes

Often, language is used to refer to subgroups of entities which instantiate a given universal but do not correspond to any subuniversal. We refer to such subgroups as ‘attribute classes’ (labeled ‘defined classes’ in [1]). Examples are: animal owned by the emperor, tuberculosis diagnosed on a Wednesday, surgical procedure performed in Albania. In some cases, terms of this sort need to be included in domain ontologies. The terms in question should then be defined as children of the corresponding genus (here: animal and tuberculosis, respectively), but they should not treated be as part of the asserted hierarchy of the ontology in question [].

One major set of examples of attributive classes involve roles. Thus ‘professor’ (defined as: a human being who has the professor role) denotes an attributive class, and so also do ‘nurse’, ‘student’, ‘colonel’ and so forth.

Attributive classes include also what we will call historical classes – classes whose members satisfy some historical condition, for example: biological father, person identified as candidate for clinical trial #2056-555, or person who has visited Pittsburgh.

For biological father, the correct form of definition is roughly as follows:

biological_father(a) =Def. a instantiates the universal human being

& a is male

& there some some zygote b

& there is some some child c

& there is some process of fertilization d

& b output_of c

& a agent_of c

& c = a.

Definitions

We distinguish between terms, which are lables for universals and attributive classes, and relational expressions, which are labels for relations []. Definitions of terms are always of the form

an S =Def. a G which Cs

where ‘S’ (for: species) is the term to be defined, ‘G’ (for: genus) is the immediate parent term of ‘S’ in the relevant BFO-conformant ontology, and ‘D’ (for: differentia) specifies what it is about the G’s which makes them S’s.

Attributive classes can be defined by using as genus any BFO-conformant universal below entity.