Ontologies? Semantic Web? OWL? – Making sense of it all

PresentersFemke.Ongenae@intec.ugent.beMatthias.Strobbe@intec.ugent.beStijn.Verstichel@intec.ugent.bewww.ibcn.intec.ugent.beINTEC Broadband Communication Networks (IBCN)Department of Information Technology (INTEC)Ghent University - IBBT

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The ontology cloud

Semantic Web

Ontology

OWL

Formal logic

Reasoning

RDF

SWRL

SPARQL

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The evolution of the Web

Connections between people

Con

nect

ions

bet

wee

n In

form

atio

n

Email

Social Networking

Groupware

JavascriptWeblogs

Databases

File Systems

HTTPKeyword Search

USENET

Wikis

Websites

Directory Portals

2010 - 2020

Web 1.0

2000 - 2010

1990 - 2000

PC Era1980 - 1990

RSSWidgets

PC’s

2020 - 2030

Office 2.0

XML

RDF

SPARQLAJAX

FTP IRC

SOAP

Mashups

File Servers

Social Media Sharing

Lightweight Collaboration

ATOM

Web 3.0

Web 4.0

Semantic SearchSemantic Databases

Distributed Search

Intelligent personal agents

JavaSaaS

Web 2.0 Flash

OWL

HTML

SGML

SQLGopher

P2P

The Web

The PC

Windows

MacOS

SWRL

OpenID

BBS

MMO’s

VR

Semantic Web

Intelligent Web

The Internet

Social Web

Web OS

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The limitations of keyword search

Amount of data

Pro

duct

ivity

of S

earc

h

Databases

2010 - 2020

Web 1.0 2000 - 2010

1990 - 2000

PC Era1980 - 1990

2020 - 2030

Web 3.0

Web 4.0

Web 2.0 The World Wide Web

The DesktopKeyword search

Natural language search

Reasoning

Tagging

Semantic SearchThe Semantic Web

The Intelligent Web

Directories

The Social Web

Files & Folders

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Semantic Web – Adding meaning to data

Different methods to add semantics to data: Tagging Statistics Linguistics Ontology – Semantic Web AI

Semantic Web: Set of open standards by the W3C to add semantics (meaning) to data

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Ontology - OWL

“An ontology is a specification of a conceptualization in the context of knowledge description”

Pizza Meathas_topping *

Is a

SalamiSpiciness

Vegetarian PizzaPizzaNot(has_topping some Meat)

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Ontology - OWL

Structured knowledge representation

Domain Application

Sharing – Reuse

Support communication

Capture knowledge formally Reasoning Extract new knowledge

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RDF – Store data as “triples”

the subject, which is an RDF URI reference or a blank node

the predicate, which is an RDF URI reference

the object, which is an RDF URI reference , a literal or a blank node

Femke IBCNWorks_at

Subject

Predicate

Object

The Semantic Web

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The semantic graph connects everything…

EmailsCompanies

Products

Services

Web Pages

Multimedia

Documents

Events

Projects

Activities

Interests

Places

People

Groups

The social graph just connects people

Better search

More targeted ads

Smarter collaboration

Deeper integration

Richer content

Better personalization

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SWRL - SPARQL

SWRL Define rules by using domain concepts Add more expressivity then pure OWL

Person(?p) ^ hasSalaryInPounds(?p, ?pounds) ^ swrlb:multiply(1.9, ?pounds, ?dollars) -> hasSalaryInDollars(?p, ?dollars)

SPARQL Query data Similar to SQL but optimized for RDF data

PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?person foaf:mbox <mailto:alice@example.net> . ?person foaf:name ?name . }

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Layered cake of the Semantic Web

OWL

SWRL & SPARQL

Reasoning

Data triples

Tutorial: Building an OWL Ontology

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Named & Disjoint Classes

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Class Hierarchy

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Object Properties

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Object Property Characteristics

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Property Domains & Ranges

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Property Restrictions

A restriction describes an anonymous class of individuals based on the relationships that members of the class participate in.

3 main categories: Quantifier Restrictions

Existential restrictions Universal restrictions

Cardinality Restrictions hasValue Restrictions

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Existential Restriction

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Reasoning

Key Features Classification:

Test whether or not one class is a subclass of another class

Consistency checking Check whether or not it is possible for a class to

have any instances

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Consistency Checking

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Necessary & Sufficient Conditions

Primitive Class Class that only has

‘necessary’ conditions Defined Class

Class that has at least one set of ‘necessary and sufficient’ conditions

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Automated Classification

Computing subclass- superclass relationships vital to keep large ontologies in logically correct state

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Universal Restrictions

Constrain the relationships along a given property to individuals that are members of a specific class

They don’t specify the existence of a relationship

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Open World Assumption

It cannot be assumed that something does not exist until it is explicitly stated that it does not exist!

Closed World Assumption (programming languages, databases, …)

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Closure Axiom

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Value Partition

Restricting the possible values for a property to an exhaustive list

Design Pattern

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Value Partition

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Cardinality Restrictions

For property P, cardinality restrictions describe the minimum, maximum or exact number of P relationships that an individual can participate in

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Qualified Cardinality Restriction

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Datatype Properties

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Data Properties

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Open World Reasoning bis

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Open World Reasoning bis

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hasValue Restriction

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Enumerated Classes

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Multiple Sets of Necessary & Sufficient Conditions

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Ontologies – more than just a datamodel … but !

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Important Consideration

ONTOLOGY≠

DATA-MODEL

ONTOLOGY=

DOMAIN-MODEL

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Three common layers

LOGIC

Ontology

Rules

Application

+/- STATIC

DYNAMIC

REUSE

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What do you need in an ontology-based application?

Data

Sources• Legacy• Ontology

A-Box• ….

Persistency• Relational DB• Files• Triple Store

Reasoning• Pellet• Fact++• …• None

Rules• Jess• Bossam• …• None

Appl’on Support• Jena• Sesame• Redland• …

SHARED ONTOLOGY MODEL

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Typical Ontology Service

MySQL

JENA D2RQ

JOSEKI

SPARQL

PopulatorA

PopulatorB

PopulatorC

PopulatorD

SPARQL

SDB

TDB

Spreadsheet

RDF123

SPARQL

PopulatorE

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D2R-Server: Treating Non-RDF Databases as Virtual RDF Graphs

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RDF123 is an application and web service to generate RDF data from spreadsheets

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Recent commercial initiatives

Ontology.com Thinking Service Models

Metatomix Semantic web-based solutions for Enterprise Resource

Interoperability TopQuadrant

Making Information Work for the Enterprise Semantic Discovery Systems

Beyond Business Intelligence, from Analytics to Discovery Oracle 11g

Open, scalable, secure and reliable RDF management

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Every feature at a certain cost

Genericness Performance

SWRL Rules

First-Order Logic Concepts

A-Box Size

Domain Modeling

Application Reuse

Questions ?PresentersFemke.Ongenae@intec.ugent.beMatthias.Strobbe@intec.ugent.beStijn.Verstichel@intec.ugent.bewww.ibcn.intec.ugent.beINTEC Broadband Communication Networks (IBCN)Department of Information Technology (INTEC)Ghent University - IBBT

Some slides and graphs borrowed from the presentation “Making sense of the Semantic Web” by Nova Spivackhttp://www.mindingtheplanet.net