A Semantic Multimedia Web (Part 2)

A Semantic Multimedia Web: Create, Annotate, Present and Share your Media Raphaël Troncy, < [email_address] > CWI, Interactive Information Access

Agenda

Semantic Web technologies

RDF: a general triple model for modeling information

RDFS / OWL: languages for representing ontologies on the web

SKOS: simple knowledge organization system

Modeling your Ontology

Methodologies for building ontologies

Tools for publishing vocabularies on the web

Linked Data

Expose you data following 4 basic principles

Re-use a growing amount of publicly open datasets

Applications powered by linked data

RDF

is the first layer of the Semantic Web standards

RDF

stands for R esource D escription F ramework

RDF

stands for R esource: pages, images, videos , ... everything that can have a URI D escription: attributes, features, and relations of the resources F ramework: model, languages and syntaxes for these descriptions

R D F

is a triple model i.e. every piece of knowledge is broken down into

( subject , predicate , object )

knowledge

take for instance the following piece of

image.jpg has for creator Raphael and depicts the elephant Ganesh

image.jpg has for creator Raphael image.jpg depicts the elephant Ganesh

( image.jpg , creator , Raphael ) ( image.jpg , depicts , Elephant Ganesh ) ( subject , predicate , object )

R D F

in the atoms of knowledge are triples of the form ( subject , predicate , object )

a triple the RDF atom Predicate Subject Object

is also a graph model to link the descriptions of resources

RDF

triples can be seen as arcs of a graph ( vertex , edge , vertex )

RDF

Raphael creator image.jpg depicts Ganesh

in resources and properties are identified by URIs

R D F http://mydomain.org/mypath/myresource

R D F

in values of properties can also be literals i.e. strings of characters

http://www.cwi.nl/~troncy#me http://purl.org/dc/elements/1.1#creator http://flickr.com/photos/rtroncy/2923/ http://xmlns.com/foaf/0.1#depicts Elephant Ganesh

nodes RDF allows blank

anonymous a resource may be i.e. not identified by a URI and noted _: xyz

e.g., there exists an image about Ganesh

http://comm.semanticweb.org/core#Image rdf:type _:x http://xmlns.org/foaf/0.1/#depicts "Ganesh"

break blank nodes the graph, they cannot be reused

name your resources and reuse existing names as much as possible

< /> has an XML syntax

R D F

don't run away

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:foaf="http://xmlns.com/foaf/0.1/" > <rdf:Description rdf:about= "http://flickr.com/photos/rtroncy/2923">

<dc:creator rdf:resource= " http://www.cwi.nl/~troncy#me "/> <foaf:depicts> Ganesh </foaf:depicts> </rdf:Description>

</rdf:RDF>

it's only for ma chi nes

open-world assumption as opposed to the closed world assumption of classical systems

in short: the absence of a triple is not significant

( image.jpg , creator , Raphael )

doesn't mean image.jpg has one creator

( image.jpg , creator , Raphael )

means image.jpg has at least one creator

if you have no other triples giving authors it does not mean they are not true .

RDF S

stands for R D F Schema

RDF S

provides primitives to write lightweight schemas for R D F triples

long way

a little drop of semantics goes a

RDF S

provides primitives to...

... define the vocabulary used in triples

... define elementary inferences

RDF S

to define classes of resources and organize their hierarchy

DOCUMENT REPORT

RDF S

to define relations between resources and organize their hierarchy

Tom Doc13 AUTHOR

CREATOR AUTHOR

RDF S

allows for multiple inheritance for classes and properties

PERSON MAN MALE

RDFS

relations have a signature

DOMAIN RANGE

RDFS

relations have a signature

... the domain is the type of the resource the relation starts from.

... the range is the type of the resource the relation ends to.

RDFS

relations with several...

... domains mean all domains apply.

... ranges mean all ranges apply.

Ranges and domains are optional

but looks like object programming,

properties

are first class citizens,

they are not defined inside classes,

they have their own hierarchy.

no overwriting

in particular a property can not be refined for sub classes of its range or domain.

multi-instantiation

a resource can have several types,

it can be the instance of several classes

like multiple lights, facets on a resource.

RDF S

provides primitives to...

... give labels ...

... give comments ...

... for classes and properties

RDF...

RDFS using the XML syntax for

<rdf:RDF xml:base="http://inria.fr/2005/humans.rdfs" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns="http://www.w3.org/2000/01/rdf-schema#> < Class rdf:ID=" Man "> < subClassOf rdf:resource="# Person "/> < subClassOf rdf:resource="# Male "/> <label xml:lang="en">man</label> <comment xml:lang="en">a male person</comment> </Class>

<rdf: Property rdf:ID=" hasMother "> < subPropertyOf rdf:resource="# hasParent "/> < range rdf:resource="# Female "/> < domain rdf:resource="# Human "/> <label xml:lang="en">has for mother</label> <comment xml:lang="en">a female parent</comment> </rdf:Property> </rdf:RDF>

RDF S

semantics : standard inference rules to derive additional triples from known statements.

example of type propagation

IF (c 2 , subClassOf , c 1 ) AND (x, type , c 2 ) THEN (x, type , c 1 )

IF (Man, subClassOf , Person) AND (Tom, type , Man) THEN (Tom, type , Person)

example of property propagation

IF (p 2 , subPropertyOf , p 1 ) AND (x, p 2 , y) THEN (x, p 1 , y)

IF (author, subPropertyOf , creator) AND (Tom, author, Report12) THEN (Tom, creator, Report12)

example of subClass transitivity

IF (c 2 , subClassOf , c 1 ) AND (c 3 , subClassOf , c 2 ) THEN (c 3 , subClassOf , c 1 )

IF (Person, subClassOf , Animal) AND (Man, subClassOf , Person) THEN (Man, subClassOf , Animal)

example of subProp transitivity

IF (p 2 , subPropertyOf , p 1 ) AND (p 3 , subPropertyOf , p 2 ) THEN (p 3 , subPropertyOf , p 1 )

IF (parent, subPropertyOf , ancestor) AND (father, subPropertyOf , parent) THEN (father, subPropertyOf , ancestor)

example of domain inference

IF (p 1 , domain , c 1 ) AND (x, p 1 , y) THEN (x, type , c 1 )

IF (author, domain , Human) AND (Tom, author, Report12) THEN (Tom, type , Human)

example of range inference

IF (p 1 , range , c 1 ) AND (x, p 1 , y) THEN (y, type , c 1 )

IF (author, range , Document) AND (Tom, author, Report12) THEN (Report, type , Document)

OWL is a new layer on top of RDFS

OWL Lite

OWL DL

OWL Full

Actually, OWL is a restriction of RDF Classes  Properties  Individuals

Semantic Web Tutorials

RDF in a nutshell

Tutorial ( credits @ Fabien Gandon )

RDFS in a nutshell

Tutorial ( credits @ Fabien Gandon )

Useful Resources

http://www.w3.org/2001/sw/

http://www.w3.org/People/Ivan/CorePresentations/

Agenda

Linked Data

Modeling Vocabularies/Ontologies

Approaches:

Ontology learning

Ontology reuse

Competency questions

Methodologies:

Uschold and Grüninger

M ETHONTOLOGY : whole process of ontology engineering

Differential principles

Semantic principles

Actor

Role of a human being

Role in making movies

Is a character in the movie

Director

Role of a human being

Role in making movies

Is not in the movie, but directs it

Generic “sèmes” Specific “sèmes”

Differential Principles Role Actor Director P3 : difference between the sibling nodes P4 : common property shared by the sibling nodes Plays in the movie Directs the movie P1: property with parent node (being a role of a human being) P2 : difference with parent node

Differential Principles

Amount to explicitly specify what is understood when using a concept

Formulate the semantic commitment that should be respected to use concepts

Extensional description of concepts Actor Linguistic semantics: Is a role: plays in a movie Denotation: {{w1: d11, d12..}, {w2: d21, d22, …}…} Director: Linguistic semantics Is a role; Directs a movie Denotation: {{w1: d11, d12..}, {w2: d21, d22, …}…} Role of a human being

Extensional red links: lattice structure is possible

Intensional black links : lattice structure is forbidden (tree)

{Woody Allen, Clint Eastwood,…} forbidden

Summary

DOE

OilEd

WebODE

OntoEdit

KAON Workbench

NeOn Toolkit

SWOOP

Protégé 4

How to support the collaborative ontology modeling and editing task?

Knoodl

Collaborative Protégé

Neologism SIOC example

Assignment

VoCamp like idea: let's model some vocabularies ...

Brainstorming: pick a domain

Choose (essential) terms related to the domain

Sketch the model (blackboard)

Find and re-use existing vocabularies

Publish your model

Agenda

Linked Data

Wake Up Video

Linked Data Principles

Tim Berners Lee [2006] ( Design Issues )

Use URIs to identify things (anything, not just documents);

Use HTTP URIs – globally unique names, distributed ownership – so that people can look up those names;

Provide useful information in RDF – when someone looks up a URI;

Include RDF links to other URIs – to enable discovery of related information

Linked Data Issues

Issues:

These are principles, not implementation advices

Many things (deliberately?) kept blurry

Non-information resource vs information resource debate

Architecture of the World Wide Semantic Web [ AWWSW ]

Ontology of Resources for Linked Data [ Halpin & Presutti ]

Content Negotiation and 303, httpRange-14 resolution

Formats:

HTML + RDF/XML vs. RDFa

The limit of content negotiation

Is conneg-ing between rdf+xml and video/* a good behavior?

Current configuration of jigsaw [ W3C Photo RDF ]

Equivalent: « Content is "equivalent" to other content when both fulfill essentially the same function or purpose upon presentation to the user » [ WAG ]