Prepare: Added Jena and Mondial, performing a test query

prepare/build.gradle

@@ -7,6 +7,9 @@ repositories {
 }
 
 dependencies {
+	implementation 'org.apache.jena:apache-jena-libs:4.4.0'
+	implementation 'org.apache.logging.log4j:log4j-core:2.17.2'
+	implementation 'org.slf4j:slf4j-simple:1.7.36'
 }
 
 version '0.1'

prepare/src/main/java/Main.java

@@ -1,7 +1,60 @@
+import org.apache.jena.query.QueryExecution;
+import org.apache.jena.query.QueryExecutionFactory;
+import org.apache.jena.query.QuerySolution;
+import org.apache.jena.query.ResultSet;
+import org.apache.jena.rdf.model.InfModel;
+import org.apache.jena.rdf.model.Model;
+import org.apache.jena.rdf.model.ModelFactory;
+import org.apache.jena.rdf.model.Resource;
+import org.apache.jena.reasoner.ReasonerRegistry;
+
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.Map;
+
 public final class Main
 {
 	public static void main(String[] args)
 	{
-		System.out.println("Hello world");
+		System.out.println("Loading knowledge graph...");
+		InfModel kg = ModelFactory.createInfModel(ReasonerRegistry.getTransitiveReasoner(), ModelFactory.createDefaultModel());
+		final InputStream mondialDataset = ClassLoader.getSystemResourceAsStream("mondial_2022_04_04.n3");
+		if (mondialDataset == null)
+		{
+			System.err.println("Impossible to open mondial dataset");
+			System.exit(1);
+		}
+		kg.read(mondialDataset, null, "TTL");
+		System.out.printf("Loaded %s triples\n", kg.listStatements().toList().size());
+
+		{
+			Map<String, Resource> countries = mondialGetEntitiesWithName(kg, "Country");
+			System.out.printf("There are %d countries in the dataset\n", countries.size());
+		}
+
+	}
+
+	private static Map<String, Resource> mondialGetEntitiesWithName(Model kg, String prefixedType)
+	{
+		Map<String, Resource> result = new HashMap<>();
+
+		String queryString = String.format("PREFIX m: <http://www.semwebtech.org/mondial/10/meta#> SELECT ?entity ?name WHERE { ?entity a m:%s ; m:name ?name. }", prefixedType);
+		try (QueryExecution execution = QueryExecutionFactory.create(queryString, kg))
+		{
+			final ResultSet resultSet = execution.execSelect();
+			while (resultSet.hasNext())
+			{
+				QuerySolution solution = resultSet.next();
+				Resource entity = solution.getResource("?entity");
+				String name = solution.getLiteral("?name").getString();
+				if (result.containsKey(name))
+				{
+					System.err.printf("Error: multiple entities with the name %s\n", name);
+					System.exit(1);
+				}
+				result.put(name, entity);
+			}
+		}
+		return result;
 	}
 }