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
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/
[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
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
“ 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/
Data in RDF