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RDF Resource Description Framework. By: Dan Johnson & Jena Block. Outline. RDF definition What is Semantic web? Search Engine Example What is RDF? Triples Vocabularies RDF/XML Why RDF?. RDF. A standard for encoding metadata and other information on the Semantic Web.

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rdf resource description framework

RDFResource Description Framework

By: Dan Johnson & Jena Block

outline
Outline

RDF definition

What is Semantic web?

Search Engine Example

What is RDF?

Triples

Vocabularies

RDF/XML

Why RDF?

slide3
RDF

A standard for encoding metadata and other information on the Semantic Web

what is semantic web
What is Semantic Web?

A project that aims to enable machines to do the searching, aggregating and combining of the Web's information without a human operator

An extension to the Web that adds new data and metadata to existing Web documents, extending those documents into data

An abstract intention to apply machine-exclusive meaning to the information on the web

Documents that are not “Semantic” are in a language specific to people

To make these documents “Semantic” we must apply a framework to the data within the document so the computer can understand it

search engine
Search Engine

Semantic Search Engine

Search:

“Tapioca Pudding”

Search for:

“Restaurants that serve Tapioca Pudding”

Search for:

“Recipes for Tapioca Pudding”

Blah blahblahblah tapioca blah blahblahpudding. Chocolate pudding, blah blahblahtapioca shake. Blah blahblahblah. Blah blahblahblahtapioca pudding.

Search

Restaurants

Menus

Desserts

Sides

Search

Recipe Sites

Desserts

Sides

what is rdf
What is RDF?

Resource Description Framework

Enables the encoding, exchange and reuse of structured metadata

A general method to break down data into smaller pieces with rules of the semantics of those pieces

A way of putting web data into a context which the computer can understand

what is rdf1
What is RDF?

We already have ways of putting web data into a context which the computer can understand

Databases use tables

XML uses hierarchies

However, these techniques can be too restrictive

slide9

The data below is too flexible to be represented by a table or

hierarchy so we use a graph

  • To describe the data in the graph in terms that the computer can understand, we describe each relationship individually
    • e.g. “vincent_donofrio” “starred_in” “the_thirteenth_floor”
triples
Triples

RDF is a method used to break down knowledge into smaller pieces called triples

Gives rules about the semantics to these pieces

Subject, predicate, object – the subject and the object are two things in the world and the predicate is the relation between the two

slide11

Subject

Object

Predicate

my_house

couch

has_a

slide12
Using triple format, we can describe any series of relationships in a way that the computer can understand

e.g. “The quick brown fox jumped over the lazy dog”

Although we’ve described the relationships in the sentence, the computer still doesn’t know what these words or phrases actually mean, to solve this problem we must make a vocabulary

vocabularies
Vocabularies

Vocabulary (n) – a list of words and phrases of a language

When we create an RDF file we need to define the terms we use

We do this using a vocabulary built for the computer

slide14
We can use vocabularies that we build or we can use existing vocabularies published by someone else

Dublin Core

rdf xml
RDF/XML

The W3C specifications define an XML format to encode RDF

<?xml version="1.0"?>

<rdf:RDF

xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:fd="http://www.fox_and_dog.org/">

<rdf:Description rdf:about=fd:Fox>

<fd:is_the_speed>"quick"</fd:is_the_speed>

<fd:is_the_color>"brown"</fd:is_the_color>

<fd:jumped_over rdf:resource=fd:Dog/>

</rdf:Description>

<rdf:Description rdf:about=fd:Dog>

<fd:is_just>lazy</fd:is_just>

</rdf:Description>

</rdf:RDF>

slide16
The RDF/XML format has the following rules:

Root element must be <RDF>

Vocabularies are referenced using XML namespace

The RDF triples are organized using the <Description> tag

The subject is named in the about attribute

The child nodes within the <Description> tag are the predicates

Their content is the object

“Dog” “is_just” “Lazy”

<rdf:Description rdf:about=fd:Dog>

<fd:is_just>lazy</fd:is_just>

</rdf:Description>

rdf is not xml
RDF is NOT XML!

RDF/XML is only one of many types of notation for RDF and is the only one that utilizes XML and XML namespace

The major difference between to two is in the data model

XML is hierarchical

RDF is relational

why rdf
Why RDF?

Allows multiple users the freedom of their own format while maintaining interoperability

RDF can be as descriptive as the English language while maintaining an organization that the computer can understand

However,

the question of how an application will retrieve these files has not yet been answered

references
References

http://www.rdfabout.com

http://www.w3.org/RDF/FAQ