2011 4IZ440 Semantic Web – RDF, SPARQL, and software APIs
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The document discusses the Semantic Web and RDF data formats. It provides an overview of RDF syntaxes like RDF/XML, N3, N-Triples, RDF/JSON, and RDFa. It also discusses software APIs for working with RDF data in languages like Java, PHP, and Ruby. The document outlines handling RDF data using statement-centric, resource-centric, and ontology-centric models, as well as named graphs. It provides examples of reading RDF data from files and querying RDF data using SPARQL.
![N3
NotaDon
@prefix
gd:
<http://rdf.data-‐vocabulary.org/#>
.
[]
a
gd:Person;
gd:name
“John
Example”;
gd:affiliation
“Sample
Corp.
Inc.”
.](https://image.slidesharecdn.com/20114iz440swrdfsparqlvyvojarskaapipublic-110228070457-phpapp02/85/2011-4IZ440-Semantic-Web-RDF-SPARQL-and-software-APIs-9-320.jpg)
![RDF/JSON
{
“_:a“
:
{
“http://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#”
:
[
{
“value“
:
“http://rdf.data-‐vocabulary.org/#Person”,
“type“
:
“uri“
}
],
“http://rdf.data-‐vocabulary.org/#name”
:
[
{
“value“
:
“John
Example“,
“type“
:
“literal“
}
],
“http://rdf.data-‐vocabulary.org/#affiliation”
:
[
{
“value“
:
“Sample
Corp.
Inc.“,
“type“
:
“literal“
}
]
}
}](https://image.slidesharecdn.com/20114iz440swrdfsparqlvyvojarskaapipublic-110228070457-phpapp02/85/2011-4IZ440-Semantic-Web-RDF-SPARQL-and-software-APIs-11-320.jpg)
![Query
SPARQL
Endpoint
(RDF.rb)
sparql
=
SPARQL::Client.new("http://dbpedia.org/sparql")
result
=
sparql.query("SELECT
?gag
WHERE
{
?series
skos:broader
<http://dbpedia.org/resource/
Category:The_Simpsons_episodes>
.
?episode
dcterms:subject
?series
.
?episode
dbpprop:blackboard
?gag
.
}
LIMIT
1000")
puts
result[rand(result.length)][:gag]](https://image.slidesharecdn.com/20114iz440swrdfsparqlvyvojarskaapipublic-110228070457-phpapp02/85/2011-4IZ440-Semantic-Web-RDF-SPARQL-and-software-APIs-34-320.jpg)
![Query
SPARQL
Endpoint
(RAP)
$client
=
ModelFactory::getSparqlClient("http://www.exampleSparqlService.net:2020/
example");
$query
=
new
ClientQuery();
$query-‐>query(‘PREFIX
skos:
<http://www.w3.org/2004/02/skos/core#>
PREFIX
dbpprop:
<http://dbpedia.org/property/>
PREFIX
dcterms:
<http://purl.org/dc/terms/>
PREFIX
rdfs:
<http://www.w3.org/2000/01/rdf-‐schema#>
SELECT
?gag
WHERE
{
?series
skos:broader
<http://dbpedia.org/resource/
Category:The_Simpsons_episodes>
.
?episode
dcterms:subject
?series
.
?episode
dbpprop:blackboard
?gag
.
}
LIMIT
1000’);
$result
=
$client-‐>query($query);
foreach($result
as
$line){
echo($line['?gag']-‐>toString());
}](https://image.slidesharecdn.com/20114iz440swrdfsparqlvyvojarskaapipublic-110228070457-phpapp02/85/2011-4IZ440-Semantic-Web-RDF-SPARQL-and-software-APIs-35-320.jpg)
2011 4IZ440 Semantic Web – RDF, SPARQL, and software APIs
- 1. The Seman)c Web RDF, SPARQL and so0ware APIs 4IZ440 Knowledge Representa4on and Reasoning on the WWW Josef Petrák | [email protected]
- 2. Worth a note § Open Data iniDave around world and Europe open staDsDcal and government data, usually in RDF format. § It has several success stories § hLp://headtoweb.posterous.com/open-‐data-‐success-‐stories § Google is integraDng RDF encoded as RDFa in pages into its search results. § UEP is not behind – DIKE research group KEG started Czech–Slovak semanDc iniDaDve called SemanDcs § And we have a RDF-‐based website deployed, see hLp://keg.vse.cz/
- 3. Outline § RDF representaDon formats § Data handling approaches § So0ware APIs overview § Approaches in examples § MoDvaDon example: web applicaDon
- 5. Syntaxes § RDF has several syntaxes. § A “graph” is the reference syntax. § The W3C endorsed file format is RDF/XML § Other file formats: § N-‐Triples § N3 § RDF/JSON § RDFa
- 6. RDF graph rdf:type gd:Person gd:name John Example gd:affiliaDon Sample Corp. Inc. PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX gd: <http://rdf.data-vocabulary.org/#>
- 7. RDF/XML <rdf:RDF xmlns:rdf=“http://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#” xmlns:gd=“http://rdf.data-‐vocabulary.org/#”> <rdf:Resource> <rdf:type rdf:resource=“http://rdf.data-‐vocabulary.org/#Person”/> <gd:name>John Example</gd:name> <gd:affiliation>Sample Corp. Inc.</gd:affiliation> </rdf:Resource> </rdf:RDF>
- 8. RDF/XML (shortened) <rdf:RDF xmlns:rdf=“http://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#” xmlns:gd=“http://rdf.data-‐vocabulary.org/#”> <gd:Person> <gd:name>John Example</gd:name> <gd:affiliation>Sample Corp. Inc.</gd:affiliation> </gd:Person> </rdf:RDF>
- 9. N3 NotaDon @prefix gd: <http://rdf.data-‐vocabulary.org/#> . [] a gd:Person; gd:name “John Example”; gd:affiliation “Sample Corp. Inc.” .
- 10. N–Triples _:a <http://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#type> <http://rdf.data-‐vocabulary.org/#Person> . _:a <http://rdf.data-‐vocabulary.org/#name> “John Example” . _:a <http://rdf.data-‐vocabulary.org/#affiliation> “Sample Corp. Inc.” . § Primarily used to defined RDF test cases § Subset of N3 NotaDon
- 11. RDF/JSON { “_:a“ : { “http://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#” : [ { “value“ : “http://rdf.data-‐vocabulary.org/#Person”, “type“ : “uri“ } ], “http://rdf.data-‐vocabulary.org/#name” : [ { “value“ : “John Example“, “type“ : “literal“ } ], “http://rdf.data-‐vocabulary.org/#affiliation” : [ { “value“ : “Sample Corp. Inc.“, “type“ : “literal“ } ] } }
- 12. RDFa <html xmlns=“http://www.w3.org/1999/xhtml” xmlns:rdf=“http://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#” xmlns:gd=“http://rdf.data-‐vocabulary.org/#”> <p typeof=“gd:Person”> <em property=“gd:name”>John Example</em> is working at <em property=“gd:affiliation”>Sample Corp. Inc.</em>. </p> </html>
- 13. Resources about RDF formats § RDF/XML § hLp://www.w3.org/TR/rdf-‐syntax-‐grammar/ § N3 NotaDon § hLp://www.w3.org/DesignIssues/NotaDon3 § hLp://www.w3.org/2000/10/swap/Primer § N–Triples § hLp://www.w3.org/TR/rdf-‐testcases/#ntriples § RDF/JSON § hLp://n2.talis.com/wiki/RDF_JSON_SpecificaDon § RDFa § hLp://www.w3.org/TR/rdfa-‐syntax/
- 14. Task #1 1. Use Google Data Vocabulary § hLp://www.data-‐vocabulary.org/Person/ 2. Created a NotaDon3 file with demo data about people
- 15. Data handling
- 16. RDF models § Statement–centric § Working with triples of ?subject ?predicate ?object § Resource–centric § Working with resources having properDes and their values § Ontology–centric § Working with classes, properDes, and individuals as defined in selected vocabulary/schema/ontology § Named graph § Triples belongs to a graph with URI name § Working with quads of ?graph ?subject ?predicate ?object
- 17. So0ware APIs
- 18. Java § Jena § hLp://openjena.org/ § hLp://sourceforge.net/projects/jena/ § Sesame § hLp://www.openrdf.org/ § Shellac RDFa Parser § hLps://github.com/shellac/java-‐rdfa
- 19. PHP § RDF API for PHP (RAP) § hLp://www4.wiwiss.fu-‐berlin.de/bizer/rdfapi/ § hLp://sourceforge.net/projects/rdfapi-‐php/ § ARC2 § hLp://arc.semsol.org/
- 20. Ruby § RDF.rb § hLp://rdf.rubyforge.org/ § hLps://github.com/bendiken/rdf § Plus various modules
- 21. Code Examples
- 22. File-‐read § Task: Read RDF data from a NotaDon3 file format into memory model.
- 23. Read N3 (Jena) InputStream is = FileManager.get().open("samples/people.n3"); Model model = ModelFactory.createDefaultModel(); RDFReader r = model.getReader("N3"); r.read(model, is, null); is.close();
- 24. Read N3 (RDF.rb) repository = RDF::Repository.new RDF::N3::Reader.open(‘samples/people.n3’) { |reader| repository << reader }
- 25. Read N3 (ARC2) $parser = ARC2::getRDFParser(); $parser-‐>parse(‘samples/people.n3'); $triples = $parser-‐>getTriples();
- 26. Read N3 (RAP) $model = ModelFactory::getDefaultModel(); $model-‐>load('samples/people.n3'); § This code won’t run, because there is N3Reader bug. § Works also for RDF/XML and N–Triples formats.
- 27. Traverse triples § Task: Take a memory model and list all or parDcular RDF triples.
- 28. Traverse triples (Jena) Model model = ModelFactory.createDefaultModel(); // Load data into model StmtIterator i = model.listStatements(); while (i.hasNext()) { Statement stmt = i.nextStatement(); Resource subject = stmt.getSubject(); Property predicate = stmt.getPredicate(); RDFNode object = stmt.getObject(); // Printing out }
- 29. Query Model (Jena) Resource rPerson = model.getResource("http://rdf.data-‐ vocabulary.org/#Person"); Property rName = model.getProperty("http://rdf.data-‐vocabulary.org/ #name"); StmtIterator si = model.listStatements(null, RDF.type, rPerson); while (si.hasNext()) { Resource r = si.nextStatement().getSubject(); StmtIterator sii = model.listStatements(r, rName, (RDFNode)null); if (sii.hasNext()) { System.out.println(sii.nextStatement().getObject().toString()); } }
- 30. Traverse triples (RDF.rb) repository = RDF::Repository.new # Load data repository.each_statement { |statement| puts statement }
- 31. Query model (RDF.rb) GD = RDF::Vocabulary.new('http://rdf.data-‐vocabulary.org/#') repository = RDF::Repository.new # Load data query = RDF::Query.new({ :person => { RDF.type => GD.Person, GD.name => :name } }) query.execute(graph).each do |person| puts "name=#{person.name}" end
- 32. Query SPARQL Endpoint § Task: Query a SPARQL endpoint and write out the data. E.g. from DBPedia, write one random blackboard gag wriLen by Bart Simpson.
- 33. Query SPARQL Endpoint (Jena) String qa = "PREFIX skos: <http://www.w3.org/2004/02/skos/core#>" + "PREFIX dbpprop: <http://dbpedia.org/property/>" + "PREFIX dcterms: <http://purl.org/dc/terms/>" + "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-‐schema#>" + "SELECT ?gag WHERE { " + "?series skos:broader <http://dbpedia.org/resource/ Category:The_Simpsons_episodes> ." + " ?episode dcterms:subject ?series ." + " ?episode dbpprop:blackboard ?gag ." + "}" + "LIMIT 1000"; Query q = QueryFactory.create(qa); QueryExecution qe = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", q); ResultSet rs = qe.execSelect(); ResultSetFormatter.out(System.out, rs, q); qe.close();
- 34. Query SPARQL Endpoint (RDF.rb) sparql = SPARQL::Client.new("http://dbpedia.org/sparql") result = sparql.query("SELECT ?gag WHERE { ?series skos:broader <http://dbpedia.org/resource/ Category:The_Simpsons_episodes> . ?episode dcterms:subject ?series . ?episode dbpprop:blackboard ?gag . } LIMIT 1000") puts result[rand(result.length)][:gag]
- 35. Query SPARQL Endpoint (RAP) $client = ModelFactory::getSparqlClient("http://www.exampleSparqlService.net:2020/ example"); $query = new ClientQuery(); $query-‐>query(‘PREFIX skos: <http://www.w3.org/2004/02/skos/core#> PREFIX dbpprop: <http://dbpedia.org/property/> PREFIX dcterms: <http://purl.org/dc/terms/> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-‐schema#> SELECT ?gag WHERE { ?series skos:broader <http://dbpedia.org/resource/ Category:The_Simpsons_episodes> . ?episode dcterms:subject ?series . ?episode dbpprop:blackboard ?gag . } LIMIT 1000’); $result = $client-‐>query($query); foreach($result as $line){ echo($line['?gag']-‐>toString()); }
- 36. Query SPARQL Endpoint (ARC2) $store = ARC2::getRemoteStore( array('remote_store_endpoint' => 'http://dbpedia.org/sparql')); $q = ‘PREFIX skos: <http://www.w3.org/2004/02/skos/core#> PREFIX dbpprop: <http://dbpedia.org/property/> PREFIX dcterms: <http://purl.org/dc/terms/> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-‐schema#> SELECT ?gag WHERE { ?series skos:broader <http://dbpedia.org/resource/ Category:The_Simpsons_episodes> . ?episode dcterms:subject ?series . ?episode dbpprop:blackboard ?gag . } LIMIT 1000’; $rows = $store-‐>query($q, 'rows');
- 37. Task #2 1. Select one of frameworks (preferably Jena) 2. Load data from your NotaDon3 file 3. Write out names and work Dtles of people
- 38. MoDvaDon Example
- 39. Knowledge Engineering Group Website § hLp://keg.vse.cz/ § RDF outside § Data dumps in RDF/XML § Web pages enriched with RDFa § RDF inside § Data created by SPARQL INSERT § Data queried by SPARQL SELECT § Data updated by SPARQL DELETE and SELECT § Data manipulated by user–friendly forms § Ongoing: data integraDon with ISIS VŠE and other department applicaDons
- 40. SPARQL: Create data INSERT INTO <http://keg.vse.cz/> { <http://keg.vse.cz/resource/event/1> rdf:type ical:Vevent . <http://keg.vse.cz/resource/event/1> ical:uid ”1" . <http://keg.vse.cz/resource/event/1> ical:summary ”IZI440" . <http://keg.vse.cz/resource/event/1> ical:dtstart ”2011-‐02-‐28" . }
- 41. SPARQL: Read data SELECT ?summary ?uid ?dtstart ?dtend WHERE { <http://keg.vse.cz/resource/event/1> rdf:type ical:Vevent . <http://keg.vse.cz/resource/event/1> ical:uid ?uid . <http://keg.vse.cz/resource/event/1> ical:summary ?summary . <http://keg.vse.cz/resource/event/1> ical:dtstart ?dtstart . OPTIONAL { <http://keg.vse.cz/resource/event/1> ical:dtend ?dtend . } }
- 42. SPARQL: Update data DELETE { <http://keg.vse.cz/resource/event/1> ?p ?o . } INSERT INTO <http://keg.vse.cz/> { <http://keg.vse.cz/resource/event/1> rdf:type ical:Vevent . <http://keg.vse.cz/resource/event/1> ical:uid ”1" . <http://keg.vse.cz/resource/event/1> ical:summary ”4IZ440" . <http://keg.vse.cz/resource/event/1> ical:dtstart ”2011-‐02-‐28" . }
- 43. References § hLp://dsic.zapisky.info/RDF/FOAF/parsingWithPHP/ § hLp://zapisky.info/?item=zverejnime-‐akademicke-‐projekty-‐ samozrejme-‐semanDcky § BOOK – John Hebeler (Author), MaLhew Fisher (Author), Ryan Blace (Author), Andrew Perez-‐Lopez (Author), Mike Dean (Foreword): Seman4c Web Programming, Wiley, 2009
- 44. QuesDons?
- 45. Thank you