Ontologies Come of Age Deborah L. McGuinness Stanford University “The Semantic Web: Why, What, and...

Ontologies Come of AgeOntologies Come of Age

Deborah L. McGuinness

Stanford University

“The Semantic Web: Why, What, and How, MIT Press, 2001”

Presented by Jungyeon, Yang

Copyright 2008 by CEBT

Outline Outline Introduction: Web’s growing needs Ontologies

Definition Ontology Spectrum

Uses of Ontology Simple Ontology (taxonomy) Structured Ontology

Ontology-based application Needs Language Environment

Conclusion


Introduction: Web’s growing needsIntroduction: Web’s growing needs

The web continues to grow at an astounding rate

It’s hard to find the exact information that we want on the web

web pages typically do not contain markup information about the contents of the page

We need to add intelligence to search

Solution: Semantic Web


Introduction: Web’s growing needsIntroduction: Web’s growing needs

Berners-Lee’s Architecture (Semantic Web Layer cake–old ver.)

In this paper, the ontology and logic layer are discussed What is the mean of them on the web

How ontologies could be generated

How we use them in applications


Ontologies: Ontologies: DefinitionDefinition

The term ontology has been in use for many years. 1720 Merriam Webster: Dates Ontology

There are two historical definition: A branch of metaphysics concerned with the nature

and relations of being A particular theory about the nature of being or the

kinds of existents

From the view point of computational audience: “A specification of a conceptualization” by

Gruber


Ontologies: Ontologies: Ontology SpectrumOntology Spectrum

Web ontologies may be viewed as a spectrum of detail in their specification.

One might visualize a simple (linear) spectrum of definitions

Catalog/ID

GeneralLogical

constraints

Terms/glossary

Thesauri“narrower

term”relation

Formalis-a

Frames(properties)

Informalis-a

Formalinstance Value

Restrs.

Disjointness, Inverse, part-of…

A finite list of terms.Controlled vocabularies

A list of terms and meanings.(natural language statements)

Additional semanticsbetween terms (Synonyms)

Should not be just “is-a”or strict subclasses

Strict subclass hierarchy


Uses of ontology : examplesUses of ontology : examples

Simple ontology

Not as costly to build and potentially more importantly, many are available.

DMOZ, for example, leverages over 35,000 volunteer editors and at publication time, had over 360,000 classes in a taxonomy

Sophisticated ontology example:

the Unified Medical Language System (UMLS), developed by the national library of medicine is a large sophisticated ontology about medical terminology

Some company such as Cycorp makes available portions of large, detailed ontologies


Uses of simple ontologyUses of simple ontology

provide a controlled vocabulary Every one can use the same vocabulary

A start for interoperability

site organization and navigation support Many web sites today expose on the left hand side of

a page the top levels of a generalization hierarchy of terms.

Categories can expand to subcategories

support expectation setting By exploring the top level categories, you can quickly

determine if the site might have your interest contents

Some of the ways that simple ontologies may be used in practice


Uses of simple ontology (Cont.)Uses of simple ontology (Cont.)

“umbrella” structures from which to extend content Some freely available ontologies are attempting to

provide the high level taxonomic organization from which many efforts may inherit terms.

Example: Universal Standard Products and Services Classification (UNSPSC)

Provide browsing support Content on a site may be tagged with terms from the

taxonomy

It can help search engines to use enhanced search capabilities


Uses of simple ontology (Cont.)Uses of simple ontology (Cont.)

search support A query expansion method may be used in order to expand a

user query with terms from more specific categories in the hierarchy

sense disambiguation support

If the same term appears in multiple places in a taxonomy, an application may move to a more general level in the taxonomy in order to find the sense of the word

Example: “Jordan” as a name of Basket-ball player and name of a country


Uses of structured ontologyUses of structured ontology

Once ontologies begin to have more structure, they can provide more power in applications.

consistency checking If ontologies contain value restrictions on the

properties, then type checking can be done within applications

Example: “Goods” has a property called “price” that has a value restriction of number

Completion Using an ontology, we can complete needed

information about things Example: “HighResolutionScreen” contains

“verticalResolution” and “horizontalResolution”


Uses of structured ontology (Cont.)Uses of structured ontology (Cont.)

Interoperability support When different users/applications uses the same set of

terms We can use equality axioms to express one term

precisely in terms of another Example: StanfordEmployee ≡ Person ∩

Employer(Stanford University)

exploit generalization/specialization information If we get too many answers for a query, by using

ontology search application can suggest specializing term

Opposite case is same.


Uses of structured ontology (Cont.)Uses of structured ontology (Cont.)

support structured, comparative, and customized search if one is looking for televisions, its properties may be

obtained in search. a comparative presentation may be made of televisions

by presenting the values of each of the properties Search interfaces can help you by showing more

detailed properties of product

The foundation for configuration support Class terms may be defined

– they contain descriptions of what kinds of parts may be in a system

Interactions between properties can be defined– filling in a value for one property can cause another value to be

filled in for another slot


Ontology-based application Needs Ontology-based application Needs

Two major concerns

Language

Environment


Ontology-based application Needs: LanguageOntology-based application Needs: Language

An ontology must be encoded in some language

As we saw, the spectrum is very wide and it contains simple and sophisticated ontologies The language should support both

More expressive = More complex ontologies = More sophisticated language needed

Solution (in 2001) : DAML+OIL DAML(DARPA Agent Markup Language) program ended

in early 2006

OIL(Ontology Inference Language) was incorporated intothe OWL

Recent : OWL (Web Ontology Language)


Ontology-based application Needs: EnvironmentOntology-based application Needs: Environment

We need an environment for ontologies to analyze, modify, and maintain an ontology over time

Some examples:

“Verity” is a topic editor to generating taxonomies

Ontolingua [Farquhar-et-al 1997] Stanford University

Chimaera [McGuinness-et-al. 2000] Stanford University

OilEd from Manchester University

[Protégé 2000] from Stanford Medical Informatics

OntoEdit


Ontology-based application Needs: Environment Ontology-based application Needs: Environment (Cont.)(Cont.)

There are some issues to consider for choosing ontology environment: Collaboration and distributed workforce

support– allow users to share a session– see each other’s work environments

Platform interconnectivity– example : Java-based applications

Scale Versioning Security

– Differing access to portions of ontology– Environment should expose portions of ontology based on

security model

Ease of use


Ontology-based application Needs: Environment Ontology-based application Needs: Environment (Cont.)(Cont.)

Analysis– To support acquisition, evolution and maintenance of ontologies

– Analysis can support user’s attention to modification

Lifecycle issues – As ontologies become larger and longer lived, it should be supported for

evolution, breaking apart, multiple namespaces etc.

Diverse user support– Allow users to customize environments as appropriate to the type of user

– Work for power users and naïve users

Presentation Style– textual, graphical, or other

Extensibility– can adapt along with the needs of the users and the projects


ConclusionConclusion

Ontologies have a wide spectrum of definitions

Ontologies grows with growth of needs

More complex ontologies can define more precise relations in taxonomies

Ontology have many types of applications

Important issues to build ontologies are

Language

Environment


My OpinionMy Opinion

Several ways that ontologies may be used in practice and issues are good references when we apply ontologies to specific application.

We have to focus on roles of an ontology

A form of an ontology is not fixed. It can be changed according to the purpose of the application.

When we use ontologies, there are some trade-offs between the practical usage and expressive power of it.

Ontologies Come of Age Deborah L. McGuinness Stanford University “The Semantic Web: Why, What, and...

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