ontology - sites.ualberta.careformat/ece720w2012/lec02_ontology.pdf · lecture 2: ontology - basics of#39# ontology a branch of metaphysics relating to the nature and relations of

of#39#

lecture 2: ontology - basics

of#39#

ontology

a branch of metaphysics relating to the nature and relations of being

a particular theory about the nature of being or the kinds of existence

ece#720,#winter'12# 2#

of#39#

ontology & history tree of Porphyry

Supreme: SUBSTANCE Differentiae: material immaterial Subordinate: BODY SPIRIT Differentiae: animate inanimate Subordinate: LIVING MINERAL Differentiae: sensitive insensitive Subordinate: ANIMAL PLANT Differentiae: rational irrational Subordinate: HUMAN BEAST Individuals: Socrates Plato Aristotle etc.

ece#720,#winter'12# 3# of#39#

ontology generic


of#39#

ontology domain-based

the subject of ontology is the study of the categories of things that exist or may exist in some domain

ece#720,#winter'12# 5# of#39#


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 from the perspective of a person who uses a specific language for the purpose of talking about the domain


of#39#

ontology domain-based – definition 1

a formal, explicit specification of a shared conceptualization

[T.Gruber, 1993]

ece#720,#winter'12# 7# of#39#


conceptualization refers to an abstract model of phenomena in the world by having identified the relevant concepts of those phenomena

explicit means that the type of concepts used, and the constraints on their use are explicitly defined


of#39#


formal refers to the fact that the ontology should be machine readable

shared reflects that ontology should capture consensual knowledge accepted by the communities

ece#720,#winter'12# 9# of#39#

ontology domain-based – definition 2 (W3C)

ontology is a term borrowed from philosophy that refers to the science of describing the kinds of entities in the world and know they are related

ece#720,#winter'12# 10#

of#39#

ontology … description of …

!  classes (“things”) in the various domains of

interest !  relationships among those “things” !  properties (attributes) that “things” should possess

ece#720,#winter'12# 11# of#39#

ontology example

ece#720,#winter'12# 12#

of#39#

ontology example

ece#720,#winter'12# 13# of#39#

ontology vs taxonomy

taxonomy the study of the general principles of scientific classification – systematics classification – especially – orderly classification of plans and animals according to their presumed natural relationships

ece#720,#winter'12# 14#

of#39#

ontology vs taxonomy

taxonomy classifies terms hierarchically, using (generalization, is-a, or type-of) relationship - no other relationships - no attributes/features describing terms

ece#720,#winter'12# 15# of#39#

ontology vs taxonomy (example)

- Linnaean living being taxonomy Kingdom: animalia Filo: chordata Subfilo: vertebrata Class: mamalia Subclass: theria Order: primata Suborder: anthropoidea Family: hominidae Genera: homo Species: sapiens

ece#720,#winter'12# 16#

of#39#

ontology vs taxonomy (example)

- directory structure in a personal computer

ece#720,#winter'12# 17# of#39#

ontology vs thesauri

thesauri contains a set of relationships among concepts, organized in a taxonomic way

it is a taxonomy with a set of semantic (binary) relationships, such as, equivalence, inverse, and association

ece#720,#winter'12# 18#

of#39#

ontology vs thesauri

not sufficient to model other (part-of, member-group, cause-effect, …) aspects of real world

the most popular thesaurus - WordNet

ece#720,#winter'12# 19# of#39#

ontology vs thesauri - WordNet

ece#720,#winter'12# 20#

of#39#


ece#720,#winter'12# 21# of#39#


ece#720,#winter'12# 22#

of#39#

ontology �unique� properties – 1

strict subconcept hierarchy organization of terms must follow the generalization relationship – is-a, type-of relationship

ece#720,#winter'12# 23# of#39#


ambiguity-free interpretation of meanings and relationships users may define properties (with values restricted to certain domains) and more expressive relationships (part-of, ……………)

ece#720,#winter'12# 24#

of#39#


the use of a controlled, finite, but extensible vocabulary

ece#720,#winter'12# 25# of#39#

ontology classification according to semantic spectrum

based on the internal structure and contents of ontolgoies

depends on the complexity and sophistication of the elements

the spectrum ranges from informal catalogues of terms to sophisticated ontologies

ece#720,#winter'12# 26#

of#39#


-  controlled vocabularies (finite lists of terms) -  glossaries (lists of terms whose meaning is

described in natural language) -  Thesauri (lists of terms … and specific relationships

between the terms)

ece#720,#winter'12# 27# of#39#


-  informal is-a hierarchies (hierarchies that use generalization relationships in an informal way – not rigorously)

-  formal is-a hierarchies (hierarchies that fully respect the generalization relationships)

ece#720,#winter'12# 28#

of#39#


-  frames (models that include classes and properties; the primitives of the frame model are classes, or frames, that have properties called slots or attributes; slots may contain default values, refer to other frames, or contain different methods)

ece#720,#winter'12# 29# of#39#


-  ontologies that express value restrictions (contain constructs for restricting the values the class properties can assume)

-  ontologies that express logical restrictions (allow first-order logic restrictions to be expressed)

ece#720,#winter'12# 30#

of#39#

ontology classification according to ontology generality

-  upper-level ontologies (describe generic concepts, such as space, time, events …)

-  domain ontologies (describe vocabulary pertaining to a given domain, by specializing the concepts provided by the upper-level ontology)

ece#720,#winter'12# 31# of#39#

ontology classification according to ontology generality

-  task ontologies (describe vocabulary required to perform generic tasks or activities, by specializing the concepts provided by the upper-level ontology)

-  applications ontologies (describe vocabulary of a specific application, whose concepts correspond to the roles performed by entities in a given domain while performing some task or activity)

ece#720,#winter'12# 32#

of#39#

ontology classification according to represented info

based on �orthogonal�, to previous slides, classification

-  knowledge-representation ontologies (provide primitive modeling elements – classes, subclasses, value, …)

-  generic and common use ontologies (represent common-sense knowledge that can be used in different domains; vocabulary that relates classes, events, space, causality, and behavior)

ece#720,#winter'12# 33# of#39#


-  upper ontologies (describe general concepts, for example SUMO)

ece#720,#winter'12# 34#

of#39#


-  domain ontologies (offer concepts that can be reused in a specific domain – medical, law, …; sth between upper and domain ontologies)

-  task ontologies (describe vocabulary related to a task or activity)

ece#720,#winter'12# 35# of#39#


-  domain-task ontologies (are task ontologies that can be reused in one specific domain)

-  method ontologies (provide definitions for concepts and relationships relevant to a process)

-  application ontologies (contain all necessary concepts to model the application in question)

ece#720,#winter'12# 36#

of#39#

ontology description languages

1967 – markup language (structure of documents

with help of tags) SGML – Standard Generalization Markup Language 1989 – HTML (HyperText Markup Language) XML (Extensible Markup Language)

ece#720,#winter'12# 37# of#39#


RDF (Resource Markup Language) – representing

information about resources in the web RDF Schema SHOE (Simple HTML Ontology Extension) Oil (Ontology Inference Layer) DAML (DARPA Agent Markup Language)

ece#720,#winter'12# 38#

of#39#


2001 – DMAL+Oil Feb 10th, 2004 – OWL (Web Ontology Language)

ece#720,#winter'12# 39#

Documents

ontology - sites.ualberta.careformat/ece720w2012/lec02_ontology.pdf · lecture 2: ontology - basics of#39# ontology a branch of metaphysics relating to the nature and relations of