Resource Description Framework(RDF)

developed by World Wide Web Consortium

(W3C)

bySatya

How do we find things in real world

• Library• Video store• PhonebookEach of these systems is based on metadatai.e. data about data. This data about data is called

metadata What about the web• Dumb, brute force method• hardly any metadata

Library Video storeTelephoneDirectory

metadata1 metadata2 metadata3

???

• Is the foundation for processing metadata.• Enables automated processing of web

resources.• Provides a generic metadata architecture.• Uses XML as its language.

RDF

Applications of RDF

• In resource discovery.

• In cataloging.

• Digital Libraries.

• Intelligent Software Agents.

• Web of trust.

RDF modelRDF model:

Presents an abstract, conceptual view framework for defining metadata.

It is based on the following concepts.

• Resources: These are the things being described by RDF

expressions. e.g.www.umr.edu or a part of it e.g.

www.umr.edu/~madrias.

• Property: Is a specific aspect, characteristic, attribute or relation used to describe a resource.

• Statement: A statement in RDF consists of

resource + property + value

subject predicate object

example

For the statement “Sanjay Madria is the creator of the web page www.umr.edu/~madrias.

We have RDF statement as

And node and arc diagram as

Subject(resource) www.umr.edu/~madrias

Predicate(property) creator

Object(literal) “Sanjay Madria”

www.umr.edu/~madrias Sanjay Madria

RDF syntaxRDF syntax is needed for the purpose of creating and exchanging the metadata.

[1]RDF ::= ['<rdf:RDF>'] description* ['</rdf:RDF>'][2]description ::= '<rdf:Description' idAboutAttr? '>' propertyElt* '</rdf:Description>‘[3] idAboutAttr ::= idAttr | aboutAttr[4] aboutAttr ::= 'about="' URI-reference '"‘[5] idAttr ::= 'ID="' IDsymbol '"‘[6] propertyElt ::= '<' propName '>' value '</' propName '>‘ | '<' propName resourceAttr '/>‘ [7] propName ::= [ NSprefix ':' ] name [8] value ::= description | string [9] resourceAttr ::= 'resource="' URI-reference '"' [10] URI-reference ::= string, interpreted per [URI][11] IDsymbol ::= (any legal XML name symbol)[12] name ::= (any legal XML name symbol)[13] NSprefix ::= (any legal XML namespace prefix)[14] string ::= (any XML text, with "<", ">", and "&" escaped)

Description: contains the statements about resource.idAboutAttr: indicates which resource is being describedidAttr: gives the anchor-id of the resourceaboutAttr:gives the URI of the resource being decribed.PropertyElt:contains the name of the property and the value of the property.PropertyName: Gives the name of the property using namesapaces.value:can be another resource or a literal.resourceAttr: Specifies some other resource that is the value of this property.IDsymbol, name:any legal name symbol.NSprefix:corresponds to XML namespacesString:corresponds to XML text.

Example:

For the statement “Sanjay Madria is the creator of the resource www.umr.edu/~madrias

We have the RDF syntax(using XML) as:

<rdf:RDF>

<rdf:Description about=“www.umr.edu/madrias”>

<s:Creator>Sanjay Madria</s:creator>

</rdf:Description>

</rdf:RDF>

RDF schemaRDF schema

Provides the mechanism for declaring properties and also defining relationship between these properties and other resources

S=rdfs:subclassOf t=rdf:type

t s t t

t t t t

t

t t t s t

s s t t t t

s

t t

rdfs: Literal

rdfs:Class

rdfs:ConstraintResource

rdfs:ConstraintPropertyrdfs:range rdfs:domain

rdfs:ContainerMembershipProperty

rdf:Property

rdfs:Resource

rdfs:type

rdfs:subPropertyOf

rdfs:subCLassof

rdfs:seeAlso

rdfs:isDefinedBy

rdfs:comment

rdfs:label

Example

s

t t

t t

t s t

s

s s

s t

s

rdf:class

xyz:Passenger Vehicle

xyz:Truck

xyz:Van

xyz:Mini Van

xyz:Motor Vehicle

rdf:Resource

Advantages:

• Interoperability of metadata• Machine understandable semantic discovery• better precision in resource discovery.• Uniform query capability for resource

discovery

Conclusion

• Distributed Information on web.• Metadata• Introduction to RDF • The various concepts of RDF.