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Ontology I
Cristian Cocos (CLIStFX)
Background: What?
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What is “Ontology”?
What is an Ontology?
Traditional answer: Theory of Everything
Several other answers, more or less related:
Theory of Existence
Theory of “What There Is”
(Description of Reality?)
Background: What?
• Taxonomizing Existence: categories of
Existence
• The properties of Existence qua Existence
• (Properties of a rabbit seen as an existing
thing, not as a (biological) organism)
• Analyzing Existence in its most general
features: the most general
attributes/properties of things, i.e. properties
that every-thing has
Background: What?
• Quotes:
• Sowa: “The subject of ontology is the study of the
categories of things that exist or may exist in some
domain. The product of such a study, called an
ontology, is a catalog of the types of things that are
assumed to exist in a domain of interest D from the
perspective of a person who uses a language L for
the purpose of talking about D.”
Background: What?
• B. Smith:
• “Ontology as a branch of philosophy is the science of what is, of the kinds
and structures of objects, properties, events, processes and relations in
every area of reality. ‘Ontology’ is often used by philosophers as a
synonym of ‘metaphysics’ (a label meaning literally: ‘what comes after the
Physics’), a term used by early students of Aristotle to refer to what
Aristotle himself called ‘first philosophy’. Sometimes ‘ontology’ is used in a
broader sense, to refer to the study of what might exist; ‘metaphysics’ is
then used for the study of which of the various alternative possible
ontologies is in fact true of reality. (Ingarden 1964) The term ‘ontology’ (or
ontologia) was coined in 1613, independently, by two philosophers, Rudolf
Göckel (Goclenius), in his Lexicon philosophicum and Jacob Lorhard
(Lorhardus), in his Theatrum philosophicum. Its first occurrence in English
as recorded by the OED appears in Bailey’s dictionary of 1721, which
defines ontology as ‘an Account of being in the Abstract’.
Background: What?
• B. Smith cont’d:
• “Ontology seeks to provide a definitive and exhaustive
classification of entities in all spheres of being. The
classification should be definitive in the sense that it can serve
as an answer to such questions as: What classes of entities
are needed for a complete description and explanation of all
the goings-on in the universe? Or: What classes of entities are
needed to give an account of what makes true all truths? It
should be exhaustive in the sense that all types of entities
should be included in the classification, including also the
types of relations by which entities are tied together to form
larger wholes.”
Background: Why?
• A related development (hardly noticed by
philosophers): the term ‘ontology’ has gained
currency in recent years in the field of computer and
information science
• Why?
• One answer: theTower of Babel problem:
• Different groups of data- and knowledge-base system
designers have their own idiosyncratic terms and
concepts by means of which they build frameworks
for information representation
Background: Why?
• Different databases may use identical labels but with
different meanings
• Alternatively the same meaning may be expressed
via different names
• How about sharing and translating?
• Problems standing in the way of putting this
information together within a single system increase
geometrically
• Methods must be found to resolve the terminological
and conceptual incompatibilities which inevitably
arise
Background: Why?
• Initially, such incompatibilities were resolved
on a case-by-case basis
• Gradually it was recognized that the provision,
once and for all, of a common reference
ontology – a shared taxonomy of entities –
might provide significant advantages over
such case-by-case resolution
Background: Why?
• Hence the term ‘ontology’ came to be used by
information scientists to describe the construction of
a canonical description of this sort
• An ontology is in this context a dictionary of terms
formulated in a canonical syntax and with commonly
accepted definitions designed to yield a lexical or
taxonomical framework for knowledgerepresentation which can be shared by different
information systems communities
Background: Why?
• More ambitiously: an ontology is a formal
theory within which not only definitions but
also a supporting framework of axioms is
included (perhaps the axioms themselves
provide implicit definitions of the terms
involved)
ULO
• (Potential) Advantages of ontology for the
purposes of information management
are/should be obvious:
• Each group of data analysts would need to
perform the task of making its terms and
concepts compatible with those of other such
groups only once – by calibrating its results in
the terms of the single canonical backbone
language
ULO
• B. Smith: “If all databases were calibrated in terms of just one
common ontology (a single consistent, stable and highly
expressive set of category labels), then the prospect would
arise of leveraging the thousands of person-years of effort
that have been invested in creating separate database
resources in such a way as to create, in more or less automatic
fashion, a single integrated knowledge base of a scale hitherto
unimagined, thus fulfilling an ancient philosophical dream of a
Great Encyclopedia comprehending all knowledge within a
single system.”
ULO
• There are obstacles standing in the way of the
construction of a single shared ontology in the
sense described
• Prodigious
• E.g.: the task of establishing a common
ontology of world history
• would require a neutral and common
framework for all descriptions of historical
facts
ULO
• That, in turn would require that all legal and
political systems, rights, beliefs, powers, and
so forth, be comprehended within a single,
perspicuous list of categories
• Not going to happen
ULO
• Other difficulties arise at the level of adoption:
• To be widely accepted an ontology must be neutral
as between different data communities
• There is a (formidable) trade-off between the
constraint of neutrality and the requirement that an
ontology be maximally wide-ranging and expressively
powerful – that it should contain canonical
definitions for the largest possible number of terms
ULO
• Solution to these dificulties: ULO
• Upper Level Ontology = an ontology that would
confine itself to the specification of such highly
general (domain-independent) categories as: time,
space, inherence, instantiation, identity, measure,
quantity, functional dependence, process, event,
attribute, boundary, and so on. (See, e.g.,
http://suo.ieee.org.)
• Aka formal ontology
ULO
This top-level ontology would then be designed
to serve as common neutral backbone, which
would be supplemented by the work of
ontologists working in more specialized
domains on, for example, ontologies of
geography, or medicine, or ecology, or law, or,
still more specifically, ontologies of built
environments (Bittner 2001), or of surgical
deeds (Rossi Mori et al. 1997)
ULO
• A formal ontology/ULO comprises a
representation of the categories of objects
and of the relationships within and amongst
categories that are to be found in any domain
of reality whatsoever
• A material or domain ontology consists of a
representation of the material categories and
relationships amongst them that are to be
found in some specific domain of reality
ULO
• …such as genetics, anatomy, plant-biology,
cell-biology, physiology, etc.
• When one sets out to construct an ontology, it
will most often be a material or domain
specific ontology that one is interested in
constructing
• However, for purposes of managing the sea of
biomedical information, the relevance of
formal ontology to the construction of
material ontologies resides in …
ULO
• … its capacity to ensure interoperability or
communication between and amongst
domain ontologies
• Hence one of the primary reasons for interest
in formal or “top-level” ontologies in the
information science community is the promise
that such ontologies hold out of making widespread interoperability possible
ULO
• Derived methodological observation: select a
formal ontology to which to cling to
• Not many domain ontologies out there
observe this rule
• That is why they are so messy
Competing Formal Ontologies
• John Sowa’s ontology (the “KR Ontology”):
Competing Formal Ontologies
• CIDOC-CRM
• Brainchild of Martin Dörr, an ACGT partner
Competing Formal Ontologies
• DOLCE: Descriptive Ontology for Linguistic and
Cognitive Engineering (http://www.loacnr.it/DOLCE.html)
• DOLCE devs. “do not intend DOLCE as a
candidate for a “universal” standard ontology”
Competing Formal Ontologies
• SUMO: Suggested Upper Merged Ontology
• created at Teknowledge Corporation
• Includes Sowa’s ontology(!)
Competing Formal Ontologies
• The crown jewel: BFO
• recognizes a basic distinction between two
kinds of entities: substantial entities or
continuants, and processual entities or
occurrents (“the great divide”)
• Corresponding to these are two basic and
distinct perspectives that can be taken on the
world, neither of which can fully represent the
features of reality represented by the other:
Competing Formal Ontologies
• SPAN and SNAP
• The SNAP portion (or perspective) of BFO
represents continuants: entities that endure
through time while maintaining their identity
• BFO manual quote:
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“The SNAP ontology recognizes three major categories of continuants: dependent continuants,
independent continuants and spatial regions. The defining feature of independent continuants is that they
are the kinds of things in which other continuants, such as qualities and dispositions, can inhere. They are
the bearers of qualities and other dependent continuants. The defining feature of dependent continuants
is that they are the kinds of things (qualities, roles, functions) that inhere in or are born by something else
(namely independent entities). Spatial regions are different from both independent and dependent
continuants in that they neither inhere in anything, nor are they themselves bearers of qualities, thus
nothing inheres in them. Each of these categories admits of further sub-divisions or sub-categories.”
Competing Formal Ontologies
• SPAN:
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“As opposed to SNAP, the SPAN portion or perspective of BFO represents
occurrents: entities that happen, unfold, or develop in time. Examples of such
entities include the process of respiration, a five mile run through the Black Forest,
a whole human life in the 19th century, the development of an embryo, the
functioning of a heart. The characteristic feature of occurrents, or processual
entities, is that they are extended both in space (they occupy a definite spatial
location at every time during which they exist), and also in time (understanding
what a processual entity is, its identiy, requires knowing about how it has been at
different times).”