Start developing for the Semantic Web with JAVA. This is an introduction how to tap into your linked data, open linked data and create flexible useful applications.

1. Developing for the
Semantic Web
by Timea Turdean
21.11.2015
#devfest15
Vienna

2. SEMANTIC WEB
&
LINKED DATA
2 http://dbpedia.org/resource/Sir_Tim_Berners_Lee
Triple
http://example.org/myProject/Triple
the form of
subject–predicate–object
expressions
<?s ?p ?o>
World Wide Web Consortium
(w3.org)
English computer scientists
RDF
http://dbpedia.org/resource/Resource_Description_Framework
http://www.w3.
org/2004/02/skos/core#de
finition
http://www.w3.org/1999/02/22-rdf-
syntax-ns#type http://example.org/Timea-
Custom-
Scheme/contained_in
http://example.org/Timea-
Custom-
Scheme/knows_to_use

3. 3

4. Place your screenshot here
4Web
Application
http://preview.poolparty.biz/sparqlingCocktails/cocktails

5. 5FEATURES &
FUNCTIONALITY
● Tap into your Linked Data endpoint
● Query Linked Data
● Display your Linked Data
● Display OPEN Linked Data
● The power of Linked Data
● BONUS *An improved search

6. Tap into your
Linked Data
endpoint
▸ data contains:
6 ▸ data is available
through a
SPARQL
endpoint

7. Tap into your
Linked Data
endpoint
<http://vocabulary.semantic-web.at/cocktails/8f09ee6f-d5b9-4b8a-aa17-b0665fae4e83>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.
org/2004/02/skos/core#Concept> .
<http://vocabulary.semantic-web.at/cocktails/8f09ee6f-d5b9-4b8a-aa17-b0665fae4e83>
<http://www.w3.org/2004/02/skos/core#prefLabel> "Brandy"@en .
<http://vocabulary.semantic-web.at/cocktails/8f09ee6f-d5b9-4b8a-aa17-b0665fae4e83>
<http://www.w3.org/2004/02/skos/core#altLabel> "Grape spirit"@en .
<http://vocabulary.semantic-web.at/cocktails/8f09ee6f-d5b9-4b8a-aa17-b0665fae4e83>
<http://www.w3.org/2004/02/skos/core#definition> "Brandy (from brandywine, derived from
Dutch brandewijnu2014"burnt wine") is a spirit produced by distilling wine. Brandy
generally contains 35u201360% alcohol by volume and is typically taken as an after-
dinner drink. Some brandies are aged in wooden casks, some are coloured with caramel
colouring to imitate the effect of aging, and some brandies are produced using a
combination of both aging and colouring."@en .
<http://vocabulary.semantic-web.at/cocktails/8f09ee6f-d5b9-4b8a-aa17-b0665fae4e83>
<http://www.w3.org/2004/02/skos/core#narrower> <http://vocabulary.semantic-web.
at/cocktails/16b625c5-3930-4cf8-a75b-b25e72f2bfb6> .
<http://vocabulary.semantic-web.at/cocktails/16b625c5-3930-4cf8-a75b-b25e72f2bfb6>
<http://www.w3.org/2004/02/skos/core#prefLabel> "Calvados"@en .
7

8. SPARQL
8 SELECT * WHERE
{
?s ?p ?o
}
SELECT * WHERE
{
?s ?p ?o
}

9. Query
Linked Data
▸ Give me all Alcoholic Beverages:
PREFIX skos:<http://www.w3.org/2004/02/skos/core#>
SELECT ?label WHERE {
<http://vocabulary.semantic-web.
at/cocktails/f3000285-36b0-4ffe-af90-
740c2dd8fff5> skos:narrower ?o .
?o skos:prefLabel ?label .
}
▸ Results:
"Brandy"@en
"Fortified wine"@en
"Gin"@en
"Liqueur"@en
"Rum"@en
"Schnapps"@en
"Tequila"@en
"Vodka"@en
"Whisky"@en
"Wine"@en
9

10. Tap into your
Linked Data
endpoint
public class SPARQLendpointConnection extends HttpClient {
URL sparqlEndpointURL = null;
NameValuePair queryParam = new NameValuePair( "query", "QUERY");
List<NameValuePair> urlParams = new ArrayList() ;
List<Header> headers = new ArrayList<>() ;
public SPARQLendpointConnection (URL sparqlEndpointURL) {
this.sparqlEndpointURL = sparqlEndpointURL ;
this.addQueryParameter( "query", "QUERY");
this .addQueryParameter( "content-type" , "application/json" );
super .getParams().setParameter( "http.protocol.version" , HttpVersion. HTTP_1_1);
super .getParams().setParameter( "http.protocol.content-charset" , "UTF-8");
}
public void addQueryParameter (String key , String value) {
if (value.equals( "QUERY")) {
this.queryParam = new NameValuePair(key , value);
} else {
this.urlParams.add(new NameValuePair(key , value));
}
} [...]
}
10

11. Display your
Linked Data
public class SPARQLendpointConnection extends HttpClient {
public TupleQueryResult runAndParseSelectQuery (String query) throws IOException {
InputStream in = null;
TupleQueryResult tqr = null;
try {
in = IOUtils. toInputStream(runSelectQuery(query)) ;
tqr = QueryResultIO. parse(in, TupleQueryResultFormat. JSON);
return tqr;
} catch (QueryResultParseException | TupleQueryResultHandlerException |
UnsupportedQueryResultFormatException ex) {
throw new IOException(ex) ;
} finally {
if (in != null) {
in.close() ;
}
}
}
}
11

12. Display your
Linked Data
public class SPARQLendpointConnection extends HttpClient {
public String runSelectQuery (String query) throws IOException {
PostMethod post = new PostMethod( this.sparqlEndpointURL .toString()) ;
NameValuePair[] params = this.urlParams.toArray(new NameValuePair[ this.urlParams.
size() + 1]);
params[(params. length - 1)] = new NameValuePair( queryParam .getName() , query);
post.setRequestBody(params) ;
for (Header h : this.headers) { post.addRequestHeader(h) ; }
int statusCode ;
String response ;
try {
statusCode = super.executeMethod(post) ;
response = post.getResponseBodyAsString() ;
if (statusCode != HttpStatus. SC_OK) {
System. out.println(statusCode) ;
}} finally {
post.releaseConnection() ;
}
return response;
}}
12

13. Tap into your
Linked Data
endpoint
import org.apache.commons.httpclient.* ;
import org.apache.commons.httpclient.methods.PostMethod ;
13
org.apache.commons.httpclient.jar
commons.io.jar
import org.apache.commons.io.IOUtils ;
sesame-query.jar
import org.openrdf.query.TupleQueryResult ;
import org.openrdf.query.TupleQueryResultHandlerException ;
sesame-queryresultio-api.jar; sesame-queryresultio-sparqljson.jar
import org.openrdf.query.resultio.QueryResultIO ;
import org.openrdf.query.resultio.QueryResultParseException ;
import org.openrdf.query.resultio.TupleQueryResultFormat ;
import org.openrdf.query.resultio.UnsupportedQueryResultFormatException ;

14. Display your
Linked Data
public void test() throws Exception {
String value = "";
SPARQLendpointConnection myConncetion = new SPARQLendpointConnection( new URL("http:
//vocabulary.semantic-web.at/PoolParty/sparql/cocktails" ));
TupleQueryResult tqr = myConnection.runAndParseSelectQuery(
"PREFIX skos:<http://www.w3.org/2004/02/skos/core#> n" +
"SELECT ?label WHERE { n" +
"<http://vocabulary.semantic-web.at/cocktails/f3000285-36b0-4ffe-af90-740c2dd8fff5>
skos:narrower ?p . n" +
"?p skos:prefLabel ?label n" +
"}");
BindingSet bs = null;
try {
while (tqr.hasNext()) {
bs = tqr.next() ;
value = bs.getValue( "label").toString() ;
System.out.println(bs.getValue( "label"));
}} finally {
tqr.close() ;
}}
14

15. Display your
Linked Data
"Brandy"@en
"Fortified wine"@en
"Gin"@en
"Liqueur"@en
"Rum"@en
"Schnapps"@en
"Tequila"@en
"Vodka"@en
"Whisky"@en
"Wine"@en
15 RESULTS

16. Display your
Linked Data
private ModelAndView mavChooseIngredients;
mavChooseIngredients = new ModelAndView( "cocktails/index" );
mavChooseIngredients .addObject( "myMenu", this.retrieveMainAlcoholicBeverages()) ;
[..]
public List<BindingSet> retrieveMainAlcoholicBeverages () throws
IOException , QueryEvaluationException {
return QueryResults. asList(myConnection .runAndParseSelectQuery(
"PREFIX skos:<http://www.w3.org/2004/02/skos/core#> n" +
"SELECT ?label WHERE { n" +
"<http://vocabulary.semantic-web.at/cocktails/f3000285-36b0-4ffe-af90-
740c2dd8fff5> skos:narrower ?p . n" +
"?p skos:prefLabel ?label n" +
"}"
));
}
16

17. Display your
Linked Data
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core " %>
<%@taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions " %>
[...]
<c:forEach items="${myMenu}" var="bindingSet ">
<li class="entity">
${bindingSet.getValue( 'label').stringValue() }
</li>
</c:forEach>
17 index.jsp

18. Display OPEN
Linked Data
DBpedia SPARQL endpoint:
▸ http://dbpedia.org/sparql
SELECT * WHERE {
<http://dbpedia.org/resource/Negroni>
<http://dbpedia.org/ontology/abstract>
?abstract
}
18

19. The POWER
of
Linked data
▸ easy change of data
▸ cost efficient
▸ graph algorithms
19

20. Place your screenshot here
20An improved SEARCH
Faceted search
http://preview.poolparty.biz/sparqlingCocktails/search

21. Thank you!
21

22. Connect
Timea Turdean
Technical Consultant, Semantic Web Company
▸ timea.turdean@gmail.com
▸ http://at.linkedin.com/in/timeaturdean
▸ http://timeaturdean.com
22
© Semantic Web Company - http://www.semantic-web.at/ and http://www.poolparty.biz/

23. ▸ LD2014 picture slide3- http://data.dws.informatik.uni-
mannheim.de/lodcloud/2014/
▸ Linked Data principles: http://www.w3.
org/DesignIssues/LinkedData.html
▸ Introduction to Semantic Web: http://timeaturdean.
com/introduction-semantic-web/
23Resources