Introduction to RDF and RDFS

BYTushar Dongare

RDF ConceptRDF Concept• RDF stands for Resource Description

Framework.

• RDF is a framework for describing resources on the web.

• RDF is designed to be read and understood by computers.

• RDF (i.e RDF/XML) is a W3C Recommendation (for Semantic Web).

• RDF is written in XML

RDF ConceptRDF ConceptHow to describe resources ?

• Decompose knowledge or fact of resource into small pieces.

• In Method and not the format.

Comparing with XML

• XML is not concerned with meaning.

• XML standard doesn't indicate how to derive a fact from a document.

• Decomposition of knowledge into small pieces is called triple (statement).

• Triple is made of three parts.

TriplesTriples

SUBJECT OBJECTPREDICATE

Triple Example Triple Example

SUBJECT PREDICATE OBJECT

I own my_house

my_house has my_computer

my_house has my_bed

my_house is_in amravati

• Subject and Object denotes the real world entities.• Predicate is relationship between them.

URI 2 Name ResourcesURI 2 Name Resources

• Names must be global.

• Names for subjects, predicates, and objects must be Uniform Resource Identifiers.

• Let tushar:tushar: abbreviate http://tushar.myhomepage.com/index.html#

• And ex: abbreviate http://example.com/

URI 2 Name ResourcesURI 2 Name Resources

RDF as a Graph

Semantic Web : Three Semantic Web : Three RulesRules• A fact is expressed as a triple of the form

(Subject, Predicate, Object).

• Subjects, predicates, and objects are given as names for entities, whether concrete or abstract, in the real world.

• Names are in the format of URIs, which are opaque and global.

Reading and Writing RDFReading and Writing RDF<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#" xmlns:edu="http://www.example.org/"><rdf:Description rdf:about="http://www.coebadnera.com"> <geo:lat>40.35</geo:lat> <geo:long>-74.66</geo:long> <edu:hasDept rdf:resource="http://www.coebadnera.com/IT#"/> </rdf:Description><rdf:Description rdf:about="http://www.coebadnera.com/IT#"> <dc:title>Department of Information Technology</dc:title> </rdf:Description></rdf:RDF>

Reading and Writing RDFReading and Writing RDF………<rdf:Description rdf:about=" http://www.coebadnera.com "> <geo:lat>40.35</geo:lat> <geo:long>-74.66</geo:long> <edu:hasDept> <rdf:Description

rdf:about="http://www.coebadnera.com/IT#"> <dc:title> Department of Information Technology

</dc:title> </rdf:Description> </edu:hasDept></rdf:Description>

Choosing The Right Choosing The Right PredicatesPredicatesWHY ?

• Piece of knowledge is not automatically interpretable.

• If two RDF documents with no URIs in common, there is no information that can be interrelated.

For Example Let consider information from Google Book and Amazon.com about book in RDF Format.

Choosing The Right Choosing The Right PredicatesPredicates

<urn:isbn:0143034650> dc:title "Pro ASP.NET 3.5"<urn:isbn:0613917472> dc:title "Laws of Cyberspace"<urn:isbn:B00005U7WO> dc:title "System Simulation"

From Google Book

<urn:isbn:0143034650> amazon:price "$20.00" <urn:isbn:0613917472> amazon:price "$30.00"

<urn:isbn:B00005U7WO> amazon:price "$40.00"

From Amazon.com

(automatically interpretable for two application)

Meshing The InformationMeshing The InformationExample : Product Vender and Reviewer

Meshup of Data

Vender 1 withProduct_XProduct_YProduct_Z

Vender 2 withProduct_YProduct_Z

Vender 3 withProduct_AProduct_BProduct_Z

Reviewer 1 forProduct_XProduct_AProduct_B

Reviewer 2 forProduct_YProduct_Z

Reviewer 3 forProduct_ZProduct_X

RDFS : RDF Schema RDFS : RDF Schema • RDFS extends RDF such that it is RDF which

describe other RDF.

• Ontologies, schemas and vocabularies which all mean roughly the same thing.

• Purpose is to show applications how some information should be interpreted.

• RDF Schema (RDFS) introduces the notion of a class.

• Here a class is a type of thing.

RDF Schema : ExampleRDF Schema : Example• rdf:type class is first higher-level predicate.

<urn:isbn:0143034650> rdf:type general:Book

<urn:isbn:0613917472> rdf:type general:Book

• One interesting class is rdf:Property

dc:title rdf:type rdf:Property

amazon:price rdf:type rdf:Property

• RDFS predicates can provide even more information like rdfs:range predicate

dc:title rdfs:range rdfs:Literal

RDF Schema : ExampleRDF Schema : Example• rdfs:subClassOf relation indicates that one

class is a sub-class of another.

Animal

Dog

rdfs:subClassOf

Criticism of RDFCriticism of RDFRDF has been criticized in 2001 on the following

grounds

• The XML syntax for RDF is too verbose.

• The triple notation simplicity introduces reading and computation disadvantages.

• RDF's ability to reify statements allows for uncertainty.

ConclusionConclusionFor Semantic Web interoperability: • All items of interest, such as information

resources, real-world objects and vocabulary terms are identified by URI references.

• URI references are dereferenceable.• Descriptions are provided using the RDF/XML

syntax.• Every RDF triple is conceived as a hyperlink

that links to related information from the same or a different source.

Thank You!

• rdfabout.com

• http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/