Resource Description Framework

STANLEY WANG SOLUTION ARCHITECT, TECH LEAD @SWANG68 http://www.linkedin.com/in/stanley-wang-a2b143b

• RDF is a W3C standard, which provides tool to describe Web resources provides interoperability between applications that exchange machine-

understandable information

• Composed of three basic elements Resources – the things being described Properties – the relationships between things Classes – the buckets used to group the things

Resource Description Framework

The elements are combined to make simple statements in the form of Triples:

<Subject> <Predicate> <Object>

Men In Black stars Will Smith <MenInBlack> <hasStar> <WillSmith>

Mary

Director

Secretary

to_be_in_

love_with

has_job

has_job

John

has_homepage

has_homepage

Ontology

RDF – Describe Semantic Web Resources

• Subject of an RDF statement is a resource • Predicate of an RDF statement is a property of a resource • Object of an RDF statement is the value of a property of a resource

RDF Statement

RDF Properties: type, subClassOf, subPropertyOf, range , domain, label,comment

Subject (resource) http://www.w3.org/Home/Lassila

Predicate (property) Creator

Object (literal) “Ora Lassila”

Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila.

RDF Example

Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila.

<rdf:RDF>

<rdf:Description about=

"http://www.w3.org/Home/Lassila">

<s:Creator>Ora Lassila</s:Creator>

</rdf:Description>

</rdf:RDF>

Predicate

RDF for Semantic Annotation

• RDF provides metadata about Web resources • Object -> Attribute-> Value triples • It has an XML syntax • Chained triples form a Graph

http://sepang.nottingham.edu.my/~bpayam/images/payam-barnaghi.png

has_image

#Payam payam@nottingh

am

has_email UNiM

has_teaching

http://www.nottingham.edu.my/CSIT/G53ELC

has_owner

<rdf:Description rdf:about=“#Payam”>

<has_email>payam@nottingham</has_email>

</rdf:Description>

http://sepang.nottingham.edu.my/~bpayam/#Payam

RDF Schema

• RDF Schema augments RDF to allow you to define vocabulary terms and the relations between those terms; • “extra meaning” to particular RDF predicates and

resources e.g., Class, subClassOf, Property, domain, range

• These terms are the RDF Schema building blocks (constructors) used to create vocabularies;

• RDF semantically extends RDF by providing a means to describe RDF Vocabularies;

RDF Schema is a W3C standard which defines vocabulary for RDF organizes this vocabulary in a typed hierarchy capable to explicitly

declare semantic relations between vocabulary terms

What does RDF Schema add?

• Defines vocabulary for RDF

• Organizes this vocabulary in a typed hierarchy

• class, subClassOf, type

• property, subPropertyOf

• domain, range

Alan Tom

Staff

Lecturer Research Assistant

subClassOf subClassOf

type

supervisedBy domain range

type

supervisedBy

Schema(RDFS)

Data(RDF)

Limitation of RDF

• RDF Schema is a vocabulary description language for describing properties and classes of RDF resources, with a semantics for generalization hierarchies of such properties and classes.

• RDFS is useful, but does not solve all possible requirements.

• Complex applications may want more possibilities: o similarity and/or differences of terms such as properties or classes o construct classes, not just name them o can a program reason about some terms? e.g. “if «Person» resources

«A» and «B» have the same «foaf:email» property, then «A» and «B» are identical”

This lead to the development of OWL (Web Ontology Language)