Semantic Web and Ontology

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Knowledge and Data Collections

Facilitates Knowledge-to-Knowledge interaction

Web of Knowledge (Semantic Web, Web 3.0)

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Communication between people

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Towards the Semantic Web

• WWW now– Humans do everything– Computers as tools– Problems abound

• WWW in the future– Computers do a lot

more– Computers work on

our behalf– Fewer problems…

How do we get there…?

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The More or Less Global Agreement about Standard Terminology and Conceptual Hierarchy for a Domain

Description is Necessary for the Interoperability in the Intelligent Web

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Motivation: machine-friendly data• Natural Language

• XML – represent structures

• Semantic Web - represent more semantics– represent structures– enable common vocabulary– associate symbols with logic interpretation for

inference

Li Ding is a person

<person>Li Ding</person>

<> </>

as seen by a person

as seen by a person as seen by a machine

as seen by a machine

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Where we are Today: the Syntactic Web

[Hendler & Miller 02]7

i.e. the Syntactic Web is…

• A place where – computers do the presentation (easy) and – people do the linking and interpreting (hard).

• Why not get computers to do more of the hard work?

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Today’s Web• Currently most of the Web content is suitable

for human use.• Typical uses of the Web today are

information seeking, publishing, and searching for people and products, shopping, reviewing catalogues, etc.

• Dynamic pages generated based on information from databases but without original information structure found in databases.

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What is the (Proposed) Solution?

Now... that should clear up a few things around here10

Semantic Web: Motivation & Features

• Current WWW was built for humans, not for machines• Hyperlinks with meaning– agents can navigate the WWW by following semantic

links• What will happen when data comes with semantics?– data from different sources can be combined• new, perhaps unforeseen opportunities and

functionality will result– machines can meaningfully use the WWW and

perform tasks on our behalf (“machine-understandable” content)

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–“An extension of the current Web in which information is given well-defined meaning, better enabling computers and people to work in cooperation.”• Sir Tim Berners-Lee et al., Scientific American, 2001:

tinyurl.com/i59p

–“…allowing the Web to reach its full potential…” with far-reaching consequences–“The next generation of the Web”

What is the Semantic Web?Scientific American Article 2001

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Some Definitions from the W3C“The Semantic Web is the representation of

data on the World Wide Web. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF), which integrates a variety of applications using XML for syntax and URIs for naming.”

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Semantic Web Layers

WebAspect

SemanticAspect

HTTP

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The Semantic Web Vision

Semantic Web

Turning the WWW into a machine understandable knowledge base

Ontologies

KnowledgeMarkup

IntelligentAgents

Applications

Documents

Databases15

What is an Ontology?A model of (some aspect of) the world• Introduces vocabulary

relevant to domain, e.g.:– Anatomy– Cellular biology– Aerospace– Dogs– Hotdogs– …

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What is an Ontology?

A model of (some aspect of) the world• Introduces vocabulary

relevant to domain• Specifies meaning (semantics)

of termsHeart is a muscular organ thatis part of the circulatory system

• Formalised using suitable logic

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Studer(98): Formal, explicit specification of a shared conceptualization

Machine readable

Concepts, properties,functions, axiomsare explicitly defined

Consensualknowledge

Abstract model of some phenomenain the world

What is an ontology?

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Ontologies – Example

OntologyF-Logic

similar

city

NeckarZugspitze

Geographical Entity (GE)

Natural GE Inhabited GE

countryrivermountain

instance_of

Germany

BerlinStuttgart

is-a

flow_through

located_in

capital_of

flow_through

flow_through

located_in

capital_of

367

length (km)

2962

height (m)

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SW: Use casesBooking a flightInteraction between office computer, flight company, travel agency, shuttle services, hotel, my calendar

Finding a restaurantInteraction between mobile device, map service, recommendation service, restaurant reservation service

Web searchCombining information from different sources to figure out whether to hire Innova

Intelligent homeFridge knows my calendar, orders food if I am planning a dinner

Intelligent cars Car knows my schedule, where and when to get gas, how not to hit other cars, what are the legal regulations

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Role of Semantic Web• Semantic Web representation mechanisms -

ideally suited to – describing people and the objects that link them

together– recording and representing the heterogeneous ties

involved. • Semantic Web -useful platform for – performing operations on diverse, distributed person-

and object-related data. • Object-centered networks and user-centric

services for generating collaborative content can serve as rich data sources for Semantic Web applications.

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Semantic Web vs. Web 2.0 (Ora Lassila)Semantic Web vs. Web 2.0 (Ora Lassila)

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