Data in RDF

Emanuele Della Valle
[email_address]
http://emanueledellavalle.org
Data in RDF

Share, Remix, Reuse — Legally
This work is licensed under the Creative Commons Attribution 3.0 Unported License.
Your are free:
to Share — to copy, distribute and transmit the work
to Remix — to adapt the work
Under the following conditions
Attribution — You must attribute the work by inserting
“ © applied-semantic-web.org” at the end of each reused slide
a credits slide stating: these slides are partially based on “Data in RDF” by Emanuele Della Valle http://applied-semantic-web.org/2010/03/02_RDF.ppt
To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/

Data Interchange: RDF

RDF in a nutshell Looking for a flexible data model
Why
Application are always changing (competitive environment)
People are always adding more features
Graceful evolution is important
Optimal: relational model
Relational model is remarkably flexible
Supports graceful evolution
Change => Add another table
Existing queries are unaffected
Easily accommodates new data
Without affecting existing queries
Allows data to be easily combined ("joined") in new ways
25+ years of relational database experience

RDF in a nutshell Resource Description Framework
The adaptation of the relational model to the Web give rise to RDF
From tuples to triples
Any relational data can be represented as triples
Row Key --> Subject
Column --> Property
Value --> Value

RDF in a nutshell Representing relational data in RDF (almost)
E.g., drug data
Represented in RDF (almost)
BB.2 Anxiolytics C 16 H 21 NO 2 Propranolol Propranololo プロプラノロール Category Formula Is a Drug Legend resource literal Name Drug Category Formula BB.2 Anxiolytics C 16 H 21 NO 2 Drug Name BB.2 Propranolol BB.2 Propranololo BB.2 プロプラノロール

RDF in a nutshell Representing relational data in RDF (almost)
Two important problems
Once out of the database internal ID (e.g., BB.2) becomes useless
Once out of the database internal names of schema element (e.g., Category) becomes useless as well
RDF solves it by using URI
Internal ID should be replaced by URI
Internal schema names should be replaced by URI
Values do (always) not need to be URI-fied
http://dbpedia.org/resource/Propranolol http://dbpedia.org/resource/Category:Anxiolytics C16H21NO2 http://www.w3.org/2004/02/skos/core#subject http://dbpedia.org/ontology/formula http://www.w3.org/2000/01/rdf-schema#label http://dbpedia.org/ontology/Drug http://www.w3.org/1999/02/22-rdf-syntax-ns#type Legend resource literal Propranolol Propranololo プロプラノロール

Which URI should we use?
Popular ones! Data merge will take place automatically!
RDF in a nutshell Representing data in RDF Q/A 1/4 http://dbpedia.org/resource/Propranolol http://dbpedia.org/resource/Category:Anxiolytics http://www.w3.org/2004/02/skos/core#subject + http://dbpedia.org/resource/Propranolol http://dbpedia.org/ontology/knownFor http://dbpedia.org/resource/Propranolol http://dbpedia.org/resource/Category:Anxiolytics http://www.w3.org/2004/02/skos/core#subject = http://dbpedia.org/ontology/knownFor http://dbpedia.org/resource/James_W._Black http://dbpedia.org/resource/James_W._Black

Where do I find popular URIs?
A difficult question with no clear answer
The best place to keep an eye on is
the Linking Open Data Project http://esw.w3.org/topic/SweoIG/TaskForces/CommunityProjects/LinkingOpenData
and in particular the following pages of the Wiki
Data Sets http://esw.w3.org/topic/TaskForces/CommunityProjects/LinkingOpenData/DataSets
Semantic Web Search Engines http://esw.w3.org/topic/TaskForces/CommunityProjects/LinkingOpenData/SemanticWebSearchEngines
Common Vocabularies http://esw.w3.org/topic/TaskForces/CommunityProjects/LinkingOpenData/CommonVocabularies
I normally use
Sindice API through sameas.org
e.g. http://sameas.org/html?q=propranolol&x=0&y=0
RDF in a nutshell Representing data in RDF Q/A 2/4

What is a value? When shall we URI-fy a value?
Literals cannot be used to merge different data set
E.g., what if we what to merge two resources based on their labels?
BRCA may refer to different thing on the Web e.g., try http://en.wikipedia.org/wiki/BRCA
URI-fy any value that can be eventually used to merge different dataset and leave the other values as literals
RDF in a nutshell Representing data in RDF Q/A 3/4 BRCA http://www.w3.org/2000/01/rdf-schema#label BRCA http://www.w3.org/2000/01/rdf-schema#label + = ?

RDF in a nutshell Other data structure in RDF
Trees can be represented in RDF
Anything can be represented in RDF

RDF in a nutshell Serializing RDF
Three alternatives to write triples, in
RDF/XML: Standard serialization in XML
<Description about=”subject”>
<property>value</property>
</Description>
e.g., http://dbpedia.org/data/Propranolol.rdf
Check-out the triples using http://www.w3.org/RDF/Validator/
NTriples: Simple (verbose) reference serialization (for specifications only) ‏
<http:// ... subject> <http:// ... predicate> “value” .
http://www.w3.org/RDF/Validator/ARPServlet?URI=http%3A%2F%2Fdbpedia.org%2Fresource%2FPropranolol&PARSE=Parse+URI%3A+&TRIPLES_AND_GRAPH=PRINT_TRIPLES&FORMAT=PNG_EMBED
N3 and Turtle: Developer-friendly serializations
:subject :property “value” .
e.g. http://dbpedia.org/data/Propranolol.n3

RDF in a nutshell Serializing RDF in Turtle - namespaces
URI terms can be abbreviated using namespaces
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix dbpedia: <http://dbpedia.org/resource/> .
@prefix dbpedia-owl: <http://dbpedia.org/ontology/> .
dbpedia:Propranolol rdf:type dbpedia-owl:Drug .
<http://www.w3.org/1999/ 02/22-rdf-syntax-ns#type> = ' a '
dbpedia:Propranolol a dbpedia-owl:Drug .

RDF in a nutshell Serializing RDF in Turtle - Literals
Literals: "Propranolol"
Literals with language tags: " プロプラノロール "@jp
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
dbpedia:Propranolol rdfs:label "Propranolol"@en .
dbpedia:Propranolol rdfs:label "Propranololo"@it .
dbpedia:Propranolol rdfs:label " プロプラノロール "@jp .
Typed literals: "3.14"^^xsd:float
dbpedia:Propranolol dbpprop:molecularWeight "259.34"^^xsd:float .

RDF in a nutshell Serializing RDF in Turtle - Convience Syntax
Abbreviating repeated subjects:
dbpedia:Propranolol dbpprop:molecularWeight "259.34"^^xsd:float .
... is the same as ...
dbpedia:Propranolol rdfs:label "Propranololo"@it ;
dbpprop:molecularWeight "259.34"^^xsd:float .
Abbreviating repeated subject/predicate pairs:
dbpedia:Propranolol rdfs:label "Propranolol"@en .
dbpedia:Propranolol rdfs:label " プロプラノロール "@cn .
... is the same as ...
dbpedia:Propranolol rdfs:label "Propranolol"@en ,
"Propranololo"@it ,
" プロプラノロール "@cn .

RDF in a nutshell Serializing RDF in XML - basics
W3C standardized an RDF/XML syntax [1]
The basic idea is to insert an XML element for each node (sobject and value) and arch (predicate)
Es.
< rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#”
xmlns:skos="http://www.w3.org/2004/02/skos/core#"
< rdf:Description
rdf:about ="http://dbpedia.org/resource/Propranolol"> < skos:subject > < rdf:Description
rdf:about ="http://dbpedia.org/resource/Category:Anxiolytics"/>
</ skos:subject >
</rdf:Description>
</rdf:RDF>
[1] RDF/XML Syntax Specification available at http://www.w3.org/TR/rdf-syntax-grammar/ dbpedia:Propranolol category:Anxiolytics skos:subject property element Root tag

RDF in a nutshell Serializing RDF in XML - abbreviation
A possible abbreviation is using rdf:resource in the property elements
Es.
< rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#”
xmlns:skos="http://www.w3.org/2004/02/skos/core#"
<rdf:Description rdf:about="http://dbpedia.org/resource/Propranolol"> <skos:subject
rdf:resource ="http://dbpedia.org/resource/Category:Anxiolytics"/>
</rdf:Description>
</rdf:RDF>

RDF in a nutshell Serializing RDF in XML - abbreviation
Encoding Literals
datatype
<rdf:Description rdf:about="http://dbpedia.org/resource/Propranolol"> <dbpprop:molecularWeight
rdf:datatype="http://www.w3.org/2001/XMLSchema#float"
>259.34 </dbpprop:molecularWeight >
</rdf:Description>
Language tag
<rdf:Description rdf:about="http://dbpedia.org/resource/Propranolol"> <rdfs:label xml:lang="it"> Propranololo </rdfs:label >
</rdf:Description>
dbpedia:Propranolol dbpprop:molecularWeight dbpedia:Propranolol rdfs:label “ Propranololo”@it "259.34"^^xsd:float

RDF in a nutshell Serializing RDF in XML – rdf:type abbreviation
It’s possible to abbreviate rdf:type
Es.
Long form
<rdf:Description rdf:about=" http://dbpedia.org/resource/Propranolol ">
<rdf:type rdf:resource="http://dbpedia.org/ontology/Drug"/>
</rdf:Description>
Abbreviated form
<dbpedia-owl:Drug rdf:about=" http://dbpedia.org/resource/Propranolol " />
dbpedia:Propranolol http://dbpedia.org/ontology/Drug rdf:type

RDF in a nutshell Serializing RDF in XML – more statements 1/3
E.g.
can be
listed
</rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Propranolol"> <skos:subject rdf:resource ="http://dbpedia.org/resource/Category:Anxiolytics"/>
</rdf:Description>
nested
<skos:subject rdf:resource ="http://dbpedia.org/resource/Category:Anxiolytics"/>
</rdf:Description>
shortened to a minimum
<dbpedia-owl:Drug rdf:about=" http://dbpedia.org/resource/Propranolol " >
</dbpedia-owl:Drug>
dbpedia:Propranolol category:Anxiolytics skos:subject http://dbpedia.org/ontology/Drug

E.g.
can be
listed
<rdf:Description rdf:about="http://dbpedia.org/resource/Propranolol">
</rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Category:Anxiolytics">
<skos:broader
rdf:resource ="http://dbpedia.org/resource/Category:Psycholeptics"/>
</rdf:Description>
nested
<skos:subject>
<rdf:Description rdf:about ="http://dbpedia.org/resource/Category:Anxiolytics">
<skos:broader
rdf:resource ="http://dbpedia.org/resource/Category:Psycholeptics"/>
</rdf:Description>
</skos:subject>
</rdf:Description>
dbpedia:Propranolol category:Anxiolytics skos:subject Category:Psycholeptics skos:broader

E.g.
Applying all abbreviations becomes
<dbpedia-owl:Drug rdf:about=" http://dbpedia.org/resource/Propranolol " >
<rdfs:label xml:lang="it">Propranololo</rdfs:label>
<skos:subject>
<skos:concept r df:about ="http://dbpedia.org/resource/Category:Anxiolytics">
<skos:broader>
<skos:concept
r df:about ="http://dbpedia.org/resource/Category:Psycholeptics"/>
</skos:broader>
</skos:concept>
</skos:subject>
</dbpedia-owl:Drug>
dbpedia:Propranolol category:Anxiolytics skos:subject Category:Psycholeptics skos:broader http://dbpedia.org/ontology/Drug skos:concept “ Propranololo”@it rdfs:label

RDF in a nutshell Merging XML files (representing an RDF model)
Suppose you have to merge the two following XML
Merging the XML trees is difficult, but being RDF …
<Drug rdf:about="Propranolol">
<skos:subject>
<skos:concept rdf:about="Anxiolytics"/>
</skos:subject >
<excretion>
<AnatomicalStructure rdf:about="Kidney"/>
</excretion>
</Drug>
<skos:concept rdf:about=" Anxiolytics "
skos:isSubjectOf=" Propranolol ">
<canDamage>
< AnatomicalStructure
rdf:about=" Kidney "/>
</canDamage>
</skos:concept>
Propranolol Anxiolytics Drug rdf : type rdf : type skos:subject Concept Kidney rdf : type AnatomicalStructure excretion Propranolol Anxiolytics rdf : type Concept Kidney rdf : type AnatomicalStructure canDamage skos:isSubjectOf

RDF in a nutshell Merging XML files 2/2
It’s (just) a matter to merge the two RDF graphs
NOTE: It works out nicely because both RDF/XML documents refer to the same resources and use the same vocabularies.
U Propranolol Anxiolytics Drug rdf : type rdf : type skos:subject Concept Kidney AnatomicalStructure canDamage excretion skos:isSubjectOf rdf : type

Publishing RDF as Linked Data Principles
Things must be identified with dereferenceable HTTP URIs.
If such a URI is dereferenced asking for the MIME-type application/rdf+xml, a data source must return an RDF/XML description of the identified resource.
Information Resources
Non-Information Resources
Besides RDF links to resources within the same data source, RDF descriptions should also contain RDF links to resources provided by other data sources

Publishing RDF as Linked Data More on Content Negotiation
Approach
E.g.
Resource identifier
http://dbpedia.org/resource/Propranolol
RDF representation describing Propranolol
http://dbpedia.org/ data /Propranolol .rdf
HTML representation describing Propranolol
http://dbpedia.org/ page /Propranolol
Test it! http://idi.fundacionctic.org/vapour

Publishing RDF as Linked Data Recipes for Serving Information as Linked Data
Recipes [1]
Serving static RDF files
Serving information stored in a DB as (virtual) RDF
Using a RDF storage with a Linked Data Interface
Wrap API to serve (virtual) RDF
[1] http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/

Publishing RDF as Linked Data Recipe 1 - Serving static RDF files 1/3
IDEA: negotiate content using Apache mod_rewrite by writing a .htaccess file
Directory layout
apachedocumentroot/
examples/
.htaccess
content/
file.html
file.rdf
Expected behavior
Requesting http://localhost/examples/file
a HTML browser is redirected to http://localhost/examples/content/file.html
a Linked Data application is redirected to http://localhost/examples/content/file.rdf

# Turn off MultiViews
Options –MultiViews
# Rewrite engine setup
RewriteEngine On
RewriteBase /examples
# Rewrite rule to serve HTML content from the vocabulary URI if requested
RewriteCond %{HTTP_ACCEPT} !application/rdf+xml.*(text/html|application/xhtml+xml)
RewriteCond %{HTTP_ACCEPT} text/html [OR]
RewriteCond %{HTTP_ACCEPT} application/xhtml+xml [OR]
RewriteCond %{HTTP_USER_AGENT} ^Mozilla/.*
RewriteRule êxample/$ content/file.html [R=303]
# Rewrite rule to serve RDF/XML content if requested
RewriteCond %{HTTP_ACCEPT} application/rdf+xml
RewriteRule êxample/ content/file.rdf [R=303]
# Rewrite rule to serve RDF/XML content by default
RewriteRule êxample/ content/file.rdf [R=303]
[source: http://www.w3.org/TR/swbp-vocab-pub/#recipe4example ]

Testing the configuration
http://localhost/examples/ file http://localhost/examples/ content/file.html http://localhost/examples/content/file.html http://localhost/examples/ file http://localhost/examples/ content/file.rdf http://localhost/examples/content/file.rdf

Publishing RDF as Linked Data Recipe 2 - DB as (virtual) RDF
General Idea
Ready to use solutions
D2R Server
http://sites.wiwiss.fu-berlin.de/suhl/bizer/d2r-server/index.html#quickstart
OpenLink Virtuoso
http://virtuoso.openlinksw.com/Whitepapers/pdf/Virtuoso_SQL_to_RDF_Mapping.pdf
http://virtuoso.openlinksw.com/Whitepapers/pdf/Deploying_Linked_Data_Final1.pdf
Triplify
http://triplify.org/Overview

Publishing RDF as Linked Data Recipe 3 - RDF storage + Linked Data Interface
General Idea
Ready to use solutions
Pubby : a Linked Data interfaces to SPARQL endpoints.
http://www4.wiwiss.fu-berlin.de/pubby/

Publishing RDF as Linked Data Recipe 4 - Wrap API to serve (virtual) RDF
General Idea
No “general” solutions, only ad hoc ones
Virtuoso Sponger : a framework for developing Linked Data wrappers (called cartridges) around different types of data sources
http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VirtSponger
http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VirtSpongerCartridgeSupportedDataSources
SIOC Exporters
http://sioc-project.org/exporters
[source http://sites.wiwiss.fu-berlin.de/suhl/bizer/pub/Bizer-ESWC2007-RDFbookmashup.pdf ]

Publishing RDF as Linked Data Which recipe should I use?
How much data do you want to serve?
several hundred RDF triples: recipe 1
Larger dataset: recipe 2, 3 and 4
How is your data currently stored?
In a relational database: recipe 2
Available through an API: recipe 4
As RDF dump: recipe 3
How often does your data change?
Frequently: recipe 2 and 4
Rarely: recipe 1 and 3

RDF in a nutshell RDF Resources
RDF at the W3C - primer and specifications
http://www.w3.org/RDF/
Semantic Web tools - community maintained list; includes triple store, programming environments, tool sets, and more
http://esw.w3.org/topic/SemanticWebTools
302 Semantic Web Videos and Podcasts - includes a section specifically on RDF videos
http://www.semanticfocus.com/blog/entry/title/302-semantic-web-videos-and-podcasts/

credits
Some slides are derived from
“ How to Publish Linked Data on the Web” by Chris Bizer, Richard Cyganiak and Tom Heath http://sites.wiwiss.fu-berlin.de/suhl/bizer/pub/LinkedDataTutorial/

http://applied-semantic-web.org	429
http://emanueledellavalle.org	106
http://applied-semantic-web.org.	6
http://webcache.googleusercontent.com	2
http://translate.googleusercontent.com	1
http://www.google.it	1

Data in RDF

by Emanuele Della Valle on Jul 04, 2010

Accessibility

Upload Details

Usage Rights

6 Embeds 545

Statistics

Data in RDF — Presentation Transcript