What is an ontology
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What is an Ontology?. No exact definition A tool to help organize knowledge Or a way to convey a theory on how to represent a class of things Examples of definitions. Webster’s Dictionary. Webster’s Third New International Dictionary defines Ontology:

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What is an Ontology?

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What is an ontology

What is an Ontology?

  • No exact definition

  • A tool to help organize knowledge

  • Or a way to convey a theory on how to represent a class of things

  • Examples of definitions

Webster s dictionary

Webster’s Dictionary

  • Webster’s Third New International Dictionary defines Ontology:

    • A science or study of being specifically, a branch of metaphysics relating to the nature and relations of being.

    • A theory concerning the kinds of entities and specifically the kinds of abstract entities that are to be admitted to a language system.



  • Dates back to 5th Century B.C. when Empedocles (490—c. 430 BCE) (http://en.wikipedia.org/wiki/Empedocles ) divided the world into four elements – earth, fire, water and air.

    • Aristotle’s (384—322 BCE) classification

  • Defined by philosophers as the nature of being “or” existence.

    • Branch of metaphysics

    • Entity categories and relationships

    • Often confused with the word epistemology, which is about knowledge and knowing

Thomas gruber

Thomas Gruber

  • “An ontology is a specification of a conceptualization”

  • The conceptualization is an abstract and simplified view of the world you want to represent, which is specified in a format based on the relationships between them.

    • Examples: hierarchy, cluster, relational diagram

The role of ontology

The Role of Ontology

  • Basic Role:

    To provide a language which allows a group of people to share information reliably in a chosen area of work

  • OWL FAQ W3C http://www.w3.org/2003/08/owlfaq

    …[ontology] has become identified with computers as a machine readable vocabulary that is specified with enough precision to allow differing terms to be precisely related

The role of ontology1

The Role of Ontology

  • Some areas of application

    • Indexing

    • Knowledge Sharing & Reuse

    • Artificial Intelligence (AI)

    • Enterprise Modeling

    • Software Design

    • Molecular Biology

    • eCommerce

    • Semantic Web….

More on the role of ontology

More on the Role of Ontology

  • Share common understanding of the structure of information among people and software agents

  • Enable reuse of domain knowledge

  • Make assumptions more explicit

  • Analyze domain knowledge

Structure of ontology

Structure of Ontology

  • Most ontologies are structured as taxonomies or hierarchies

  • Basic ontology has two classes of elements: the entities and the relationships between them

    • Organized according to axioms or rules that control how the world will be defined.

Important facts

Important Facts

  • What exists is only what is represented in the ontology

  • Most ontologies focus on a specific area to conceptualize (e.g. subject thesauri)

  • Must be updated to keep up with dynamic world

  • No set discipline or methodology!

Shoe ontology project

SHOE Ontology project –

  • Possible to build an ontology for anything

  • Simple HTML Ontology Extensions (SHOE) Project (http://www.cs.umd.edu/projects/plus/SHOE/)

  • Ontology to organize the Web

Ontologies from shoe

Ontologies from SHOE

Beer Ontology


  • Use existing ontologies for base definitions, i.e. organizations, liquid, event

  • Assume inheritance

  • Document Ontology


  • Additional ontologies

    Additional Ontologies

    • WordNet


    • Sharable Ontology Library


    • UMDL Ontology Concept Descriptions


    Ontology continuum

    Ontology continuum

    Classical view of ontology/language


    Simple thesauri/ deeper taxonomies low level full/intricate

    Key word CV thesauri onotologies ontologies

    Lists (WordNet)(OWL)

    Formal Ontologies

    Another ontology continuum d l mcguinness 2003

    Another ontology continuum (D.L. McGuinness, 2003)

    Basic steps for constructing an ontology

    Basic steps for constructing an Ontology

    • Determine the scope and establish boundaries

      • W,w, w, w… (who what where when…?)

      • Implementation environment

    • Check for existing ontologies – borrow or build

    • Determine

      • categories, top nodes,

      • specific instances bottom up, or

      • combination approach

    Basic steps for constructing an ontology1

    Basic steps for constructing an Ontology

    • Identify vocabulary [concept] sources

    • Determine relationships, organic

      • (can have more than 1 type relationship)

    • Build… and grow

    • Link to other ontologies

    • Test the effectiveness

    Ontologies and logic

    Ontologies and logic

    First Order Predicate Logic

    • Inferences

      Man is mortal

      Aristotle is a man


      .̇. Aristotle is mortal

    Another fopl example

    Another FOPL example

    (First Order Predicate Logic)

    Ndenotes unread e-mail

    Nappears by message yin inboxx


    .̇. Message yis………. (an unread e-mail)

    Multiple inheritance

    Multiple inheritance

    (p. 13 of ontology 101)

    • A class can be a subclass of several classes

    • Suppose you want a class Dessert wine

    • Port is both a Red wine and a Dessert wine

    • Port, therefore, has to be defined as having two superclasses: Red wine and Dessert Wine

    Red wine




    Multiple inheritance1

    Multiple inheritance

    (p. 13 of ontology 101)

    • .̇. All instances of the Port class are instances of both Red wine and Dessert Wine

      • Port will inherit its slots and their facets from both parents

        • Value of sweet, from sugar slot from the “Dessert wine class”

        • Value of for color of “red” from “Tannin level slot” for “Red wine class”

    Unified medical language system umls

    Unified Medical Language System (UMLS)


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