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ARIN – KR Practical 1, Part 2

RDF

Some of these slides are based on tutorial by Ivan Herman (W3C) reproduced here with kind permission. All changes and errors are mine.

Suresh Manandhar, Dimitar Kazakov

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Lecture Overview

Overview RDF

RDF examples

RDF tools

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Need a language to describe graphs

Besse, Christianne

Le palais des miroirsf:original

f:nom

f:traducteur

f:auteur

f:titre

http://…isbn/2020386682

f:nom

Ghosh, Amitav http://www.amitavghosh.com

The Glass Palace

2000

London

Harper Collins

a:title

a:year

a:city

a:p_name

a:namea:homepage

a:author

a:publisher

http://…isbn/000651409X

http://…foaf/Personr:type

r:type

http://dbpedia.org/../Amitav_Ghosh

http://dbpedia.org/../The_Hungry_Tide

http://dbpedia.org/../The_Calcutta_Chromosome

http://dbpedia.org/../Kolkata

http://dbpedia.org/../The_Glass_Palace

r:type

foaf:name w:reference

w:author_of

w:author_of

w:author_of

w:born_in

w:isbn

w:long w:lat

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RDF stands for Resource Description

Framework

RDF is a language for describing labelled

graphsnodes are URIs (all web applications understand these)

edges can have labels which are also URIs

allows namespaces

+ additional datatypes:Containers

Strings, Decimals, Floats etc from XML Schema

RDF provides this

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RDF triples

An RDF Triple (subject,predicate,object) is such that: “s”, “p” are URI-s, ie, resources on the Web; “o” is a URI or a

literal“s”, “p”, and “o” stand for “subject”, “property” or “predicate”, and

“object” here is the complete triple:

RDF is a general model for such triples (with machine

readable formats like RDF/XML, Turtle, N3, RDFa,

Json, …)

(<http://…isbn…6682>, <http://…/original>, <http://…isbn…409X>)

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Resources can use any URIhttp://www.mysite.com

http://www.example.org/file.html#home

http://www.example.org/form?a=b&c=d

RDF triples form a directed, labelled graph

(the best way to think about them!)

RDF triples (cont.)

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A simple RDF example (in Turtle)

@prefix my: <http://mysite.com/>@prefix dc: <http://dublincore.org/documents/dces/> .

<http://…/isbn/2020386682> dc:title "Le palais des mirroirs"@fr ; my:original <http://…/isbn/000651409X> .

my:originaldc:titl

e

http://…isbn/2020386682

Le palais des miroirs http://…isbn/000651409X

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Note: Turtle

@prefix my: <http://mysite.com/>@prefix dc: <http://dublincore.org/documents/dces/> .

<http://…/isbn/2020386682> dc:title "Le palais des mirroirs"@fr ; my:original <http://…/isbn/000651409X> .

is expanded as:

<rdf:Description rdf:about="http://…/isbn/2020386682"> <dc:title xml:lang="fr">Le palais des mirroirs</dc:title> <my:original rdf:resource="http://…/isbn/000651409X"/></rdf:Description>

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= Same RDF example (in RDF/XML)

<rdf:Description rdf:about="http://…/isbn/2020386682"> <dc:title xml:lang="fr">Le palais des mirroirs</dc:title> <my:original rdf:resource="http://…/isbn/000651409X"/></rdf:Description>

my:originaldc:titl

e

http://…isbn/2020386682

Le palais des miroirs http://…isbn/000651409X

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= Same RDF example (in RDFa)

<p about="http://…/isbn/2020386682">The book entitled“<span property=“dc:title" lang="fr">Le palais des mirroirs</span>” is the French translation of the “<span rel=“my:original" resource="http://…/isbn/000651409X">GlassPalace</span>”</p> .

my:originaldc:titl

e

http://…isbn/2020386682

Le palais des miroirs http://…isbn/000651409X

RDFa is a mechanism to allow embedding RDF meta-data within a HTML page

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URIs made the merge possible

URIs ground RDF semanticsinformation can be retrieved using existing tools

this makes the “Semantic Web”, well… “Semantic Web”

URIs play a fundamental role

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RDF principles

Every node is a URI or a literal

Every edge is a URI

i.e. ground all data without exception

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Namespaces

Namespaces are URIs that publish a

vocabulary of terms

For example, the Dublin Core is a well

known namespace for common meta-data

items such as author, title etc.

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Some common namespaces

foaf: http://xmlns.com/foaf/spec/

dc: http://dublincore.org/documents/dces/

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

rdfs: http://www.w3.org/2000/01/rdf-schema#

owl: http://www.w3.org/2002/07/owl#

geonames: http://www.geonames.org/ontology#

dbpedia: http://dbpedia.org/resource/

(http://mappings.dbpedia.org/server/ontology/classes/

http://dbpedia.org/Datasets/Properties/)

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Dublin Core Elements

Title

Author/creator

Subject/keywords

Description

Publisher

Other Contributor

Date

Resource type

Format

Resource Identifier

Source

Language

Relation

Coverage

Rights management

http://dublincore.org/documents/dces/

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RDF Elements

Syntax names

rdf:RDF, rdf:Description,

rdf:ID, rdf:about,

rdf:parseType,

rdf:resource, rdf:li,

rdf:nodeID, rdf:datatype

Class names

rdf:Seq, rdf:Bag, rdf:Alt,

rdf:Statement, rdf:Property,

rdf:XMLLiteral, rdf:List

Property names

rdf:subject, rdf:predicate,

rdf:object, rdf:type,

rdf:value,

rdf:first, rdf:rest_n

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

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For new concepts

Create your own namespace

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Consider the following statement:“the publisher is a «thing» that has a name and an address”

Until now, nodes were identified with a URI.

But…

…what is the URI of «thing»?

“Internal” nodes

London

Harper Collins

a:city

a:p_name

a:publisherhttp://…isbn/000651409X

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One solution: create an extra URI

<rdf:Description rdf:about="http://…/isbn/000651409X"> <a:publisher rdf:resource="urn:uuid:f60ffb40-307d-…"/></rdf:Description><rdf:Description rdf:about="urn:uuid:f60ffb40-307d-…"> <a:p_name>HarpersCollins</a:p_name> <a:city>HarpersCollins</a:city></rdf:Description>

The resource will be “visible” on the Web care should be taken to define unique URI-s

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Or Internal identifier (“blank nodes”)<rdf:Description rdf:about="http://…/isbn/000651409X"> <a:publisher rdf:nodeID="A234"/></rdf:Description><rdf:Description rdf:nodeID="A234"> <a:p_name>HarpersCollins</a:p_name> <a:city>HarpersCollins</a:city></rdf:Description>

Internal = these resources are not visible outside

<http://…/isbn/2020386682> a:publisher _:A234._:A234 a:p_name "HarpersCollins".

London

Harper Collins

a:city

a:p_name

a:publisherhttp://…isbn/000651409X

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Blank nodes require attention when mergingblanks nodes with identical nodeID-s in different graphs are different

implementations must be careful…

Many applications prefer not to use blank

nodes and define new URI-s “on-the-fly”

From a logic point of view, blank nodes

represent an “existential” statement “there is a resource such that…”

More on blank nodes

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Closer look – An exampleTask – to build a knowledge base for an online

camera shop using RDF

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Closer look – An example

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-

ns#> .

@prefix : <http://www.shop.com/camera#> .

@prefix dbpedia: <http://www.dbpedia.org/resource/> .

:Nikon_D300 rdf:type :DSLR.

:Nikon_D300 :manufactured_by dbpedia:Nikon.

:Nikon_D300 :model "D300".

:Nikon_D300 :weight "0.6_kg".

Task – to build a knowledge base for an online camera

shop using RDF

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Closer look – An example

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

.

@prefix : <http://www.shop.com/camera#> .

@prefix dbpedia: <http://www.dbpedia.org/resource/> .

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

:Nikon_D300 rdf:type :DSLR.

:Nikon_D300 :manufactured_by dbpedia:Nikon.

:Nikon_D300 :model "D300".

:Nikon_D300 :weight "0.6_kg".

:Nikon_D300 :reviewed_by _:x1.

_:x1 foaf:givenname "John".

_:x1 foaf:family_name "Smith”.

Blank node – to add reviewer “John Smith”

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Closer look – An example

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

@prefix : <http://www.shop.com/camera#> .

@prefix dbpedia: <http://www.dbpedia.org/resource/> .

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

:Nikon_D300 rdf:type :DSLR.

:Nikon_D300 :manufactured_by dbpedia:Nikon.

:Nikon_D300 :model "D300".

:Nikon_D300 :weight "0.6_kg".

:Nikon_D300 :reviewed_by _:x1.

_:x1 foaf:givenname "John".

_:x1 foaf:family_name "Smith".

:Nikon_D300 :bought_by _:x1.

Co-reference – Buyer and reviewer are the same

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Closer look – An example

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Closer look – An example

### This info can visible to all customers

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

@prefix : <http://www.shop.com/camera#> .

@prefix dbpedia: <http://www.dbpedia.org/resource/> .

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

:Nikon_D300 rdf:type :DSLR.

:Nikon_D300 :manufactured_by dbpedia:Nikon.

:Nikon_D300 :model "D300".

:Nikon_D300 :weight "0.6_kg".

:Nikon_D300 :reviewed_by :Reviewer_1.

:Reviewer_1 foaf:givenname "John".

:Reviewer_1 foaf:family_name "Smith”.

Use separate ids – for buyer and reviewer

Public info vs Private info

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Closer look – An example

### This info is stored in private internal db

:Nikon_D300 :bought_by :Cust_5636.

:Cust_5636 foaf:givenname ”Sally".

:Cust_5636 foaf:family_name ”Douglas”.

:Cust_5636 :address_line1 ”Heslington Lane”.

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Converting Turtle to RDF/XML

cwm --n3 camera.rdf.turtle --rdf > camera.rdf.rdf

Use Python script cwm (available on your machine, and also

from:

http://www.w3.org/2000/10/swap/doc/cwm.html)

Use Notation3 (N3) to rdf conversion

Notation3 is very similar to Turtle format though not identical

Use http://www-module.cs.york.ac.uk/arin/camera.rdf.turtle - right

click on the link, then select Save linked file as

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Using RDF/XML validator

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Using RDF/XML validator

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Visualising RDF graph

rdfdot -ttl camera.rdf.turtle > camera.rdf.dot

Use RDF to dot converter from CPAN (Perl Repository):

RDF-Trine-Exporter-GraphViz

Comes with command-line tool: rdfdot (you’ve got it)

Use Graphviz visualiser to view the graph

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Visualising RDF graph

Use Graphviz visualiser to view the graph

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Turtle shortcuts

:Nikon_D300 rdf:type :DSLR.

:Nikon_D300 :manufactured_by dbpedia:Nikon.

:Nikon_D300 :model "D300".

:Nikon_D300 :weight "0.6_kg".

:Nikon_D300 :reviewed_by :Reviewer_1.

Use of semicolon;

The following two are equivalent:

:Nikon_D300 rdf:type :DSLR;

:manufactured_by dbpedia:Nikon;

:model "D300”;

:weight "0.6_kg”;

:reviewed_by :Reviewer_1.

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Using shared vocabularies/ontologies

“Knowledge Engineering” is the task of maintaining

and designing reusable knowledge bases

Using shared vocabularies allows

applications/databases to be more resilient to future

changes

In our example, we could be more careful with the

using any vocabulary that is specific to only site

specific, e.g.: :Nikon_D300

:manufactured_by

:model

:weight

:reviewed_by