Down and Dirty with RDF and SPARQL (Part 2)

Erich BremerStony Brook Semantic Web Meetup

April 15, 2015

SPARQLselect, construct, ask, and describe

Directors and actorslinked through movies

http://dbpedia.org/sparql

Star Wars

Harrison Ford

George Lucas

Ender’s Game

Gavin Hood X-Men Origins: Wolverine

Hugh Jackman

Rise of the Guardians

Peter Ramsey

Eye in the Sky

Alan Rickman

Harry Potter

The Anatomy of a SPARQL query

<prefixes><command> <results clause> where {<triple pattern>}<optional query modifier>

“where” is optional

select SPARQL queryselect * where {

?film <http://dbpedia.org/ontology/director> ?director .?film a <http://dbpedia.org/ontology/Film> .?film <http://dbpedia.org/ontology/starring> ?actor

} limit 100

results

prefix dbp: <http://dbpedia.org/ontology/>select * where {

?film dbp:director ?director .?film a dbp:Film .?film dbp:starring ?actor

}limit 100

adding prefix name spaces

prefix dbp: <http://dbpedia.org/ontology/>select * where {?film dbp:director ?director;

a dbp:Film;dbp:starring ?actor

} limit 100

using predicate lists

prefix : <http://dbpedia.org/ontology/>select * where {?film :director ?director;

a :Film;:starring ?actor

} limit 100

using default name space “:”

prefix : <http://dbpedia.org/ontology/>select ?film ?director ?actor where {?film :director ?director;

a :Film;:starring ?actor

} limit 100

specifying variables in select clause

prefix : <http://dbpedia.org/ontology/>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>select ?title ?film ?director ?actor where {?film :director ?director;

a :Film;:starring ?actor;rdfs:label ?title

} limit 100

adding additional predicates

prefix : <http://dbpedia.org/ontology/>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>select ?title ?film ?director ?actor where {?film :director ?director;

a :Film;:starring ?actor .optional {?film rdfs:label ?title}

} limit 100

optional clause

prefix : <http://dbpedia.org/ontology/>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>select ?title ?film ?director ?actor where {?film :director ?director;

a :Film;:starring ?actor;rdfs:label ?titlefilter(lang(?title)="en")

} limit 100

adding a language filter

prefix : <http://dbpedia.org/ontology/>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>

select ?title ?film ?director ?actor where {?film :director ?director;

a :Film;:starring ?actor;rdfs:label ?titlefilter(lang(?title)="en")

}order by asc(?title)limit 100

ordering the results

results

prefix : <http://dbpedia.org/ontology/>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>construct {?film rdfs:label ?title} where {?film :director ?director;

a :Film;:starring ?actor;rdfs:label ?titlefilter(lang(?title)="en")

} limit 10

construct SPARQL query

results

@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .<http://dbpedia.org/resource/Alraune_(1918_film)> rdfs:label "Alraune (1918 film)"@en .<http://dbpedia.org/resource/Alraune_(1928_film)> rdfs:label "Alraune (1928 film)"@en .<http://dbpedia.org/resource/April_Love_(film)> rdfs:label "April Love (film)"@en .<http://dbpedia.org/resource/Ascendancy_(film)> rdfs:label "Ascendancy (film)"@en .<http://dbpedia.org/resource/Chervona_Ruta_(film)> rdfs:label "Chervona Ruta (film)"@en .

prefix : <http://dbpedia.org/ontology/>prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>ask where {?film :director ?director;

a :Film;:starring ?actor;rdfs:label ?titlefilter(lang(?title)="en")

}

ask SPARQL query

Does the pattern exist true or false?

describe <http://dbpedia.org/resource/Star_Wars_(film)>

describe SPARQL query<http://dbpedia.org/resource/Star_Wars_(film)>

select * where {<http://dbpedia.org/resource/Star_Wars_(film)> ?p ?o

}

Kind of a short hand for:

“A free and open source Java framework for building Semantic Web and Linked Data applications.”

https://jena.apache.org/

Jena – Core RDF API Library

ARQ – SPARQL engineTDB – Native Quad/triple storeFuseki – implements http SPARQL protocol on TDB and provide SPARQL Endpoint

Ontology API – Web Ontology Language (OWL)Inference API – RDF reasoning

Apache Jena<http://dbpedia.org/resource/Star_Wars_(film)>

ParameterizedSparqlString pss = new ParameterizedSparqlString("prefix : <http://dbpedia.org/ontology/>\n " + "prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +"select ?title ?film ?director ?actor where {\n" +

"?film :director ?director; a :Film; :starring ?actor; rdfs:label ?title\n" +"filter(lang(?title)=\"en\") order by asc(?title) limit 100");

QueryExecution qe = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", pss.asQuery(), "http://dbpedia.org");

ResultSet rs = qe.execSelect();while (rs.hasNext()) {

QuerySolution qs = rs.next();

String film = qs.getResource("film").toString();String title = qs.getLiteral("title").toString();System.out.println(film+" "+title);

}

Apache Jena – Select Example<http://dbpedia.org/resource/Star_Wars_(film)>

ParameterizedSparqlString pss = new ParameterizedSparqlString("prefix : <http://dbpedia.org/ontology/>\n" +"prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +

"construct {?film rdfs:label ?title} where {\n" +"?film :director ?director;\n" +" a :Film;\n" +

" :starring ?actor;\n" +" rdfs:label ?title\n" +" filter(lang(?title)=\"en\")} limit 100");

QueryExecution qe = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", pss.asQuery(), "http://dbpedia.org");

Model m = qe.execConstruct();System.out.println("Triples loaded : "+m.size());

m.write(System.out,null,"TTL");

Apache Jena – Construct Example<http://dbpedia.org/resource/Star_Wars_(film)>

ParameterizedSparqlString pss = new ParameterizedSparqlString("prefix : <http://dbpedia.org/ontology/>\n" +"prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n" +

"ask where {\n" +"?film :director ?director;\n" +" a :Film;\n" +

" :starring ?actor;\n" +" rdfs:label ?title\n" +" filter(lang(?title)=\"en\")\n" +

"}");QueryExecution qe = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", pss.asQuery(),

"http://dbpedia.org");boolean answer = qe.execAsk();

System.out.println(answer);

Apache Jena – Ask Example<http://dbpedia.org/resource/Star_Wars_(film)>

ParameterizedSparqlString pss = new ParameterizedSparqlString("describe <http://dbpedia.org>");QueryExecution qe = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", pss.asQuery(),

"http://dbpedia.org");

Model m = qe.execDescribe();System.out.println("Triples loaded : "+m.size());m.write(System.out,null,"TTL");

Apache Jena – Ask Example<http://dbpedia.org/resource/Star_Wars_(film)>

Any questions?

To be continued next month…Part 3