skos:hasTopConcept, skos:narrower, skos:broader will be inferred from

inverse relations.

HIStream-SKOS/examples/test-ontology.ttl

@@ -73,3 +73,17 @@ dwh:String a owl:Restriction ;
 			] ;
 	skos:prefLabel	"Decimal_label_en"@en ;
 	skos:notation	"T:type:dec" .
+
+# Test inferred topConcept and narrower
+:OtherScheme a skos:ConceptScheme .
+
+:OtherTop a skos:Concept ;
+	skos:inScheme	:OtherScheme ;
+	skos:topConceptOf	:OtherScheme ;
+	skos:prefLabel "OtherTop_label_en"@en .
+
+:OtherSub a skos:Concept ;
+	skos:inScheme	:OtherScheme ;
+	skos:broader	:OtherTop ;
+	skos:prefLabel "OtherSub_label_en"@en ;
+	skos:notation	"other" .

HIStream-SKOS/src/main/java/de/sekmi/histream/ontology/skos/ConceptImpl.java

@@ -25,6 +25,16 @@ public class ConceptImpl implements Concept {
 		this.res = concept;
 	}
 	
+	@Override 
+	public boolean equals(Object other){
+		if( other.getClass() != ConceptImpl.class )return false;
+		return res.equals(((ConceptImpl)other).res);
+	}
+	@Override
+	public int hashCode(){
+		return res.hashCode();
+	}
+	
 	@Override
 	public Concept[] getNarrower() throws OntologyException {
 		return store.getNarrower(this);

HIStream-SKOS/src/main/java/de/sekmi/histream/ontology/skos/Store.java

@@ -8,6 +8,7 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
+import java.util.logging.Logger;
 
 import org.openrdf.model.Literal;
 import org.openrdf.model.Resource;
@@ -36,10 +37,14 @@ import de.sekmi.histream.ontology.skos.transform.Rule;
 import de.sekmi.histream.ontology.skos.transform.TransformationRules;
 
 public class Store implements Ontology, Plugin {
+	private static final Logger log = Logger.getLogger(Store.class.getName());
 	private Repository repo;
 	private RepositoryConnection rc;
 	private final static Concept[] noConcepts = new Concept[]{};
 	private long lastModified;
+	private Resource inferredContext;
+	// SKOS scheme to enforce unique notations
+	private Resource scheme;
 	
 	/**
 	 * Plugin constructor which accepts configuration parameters.
@@ -47,6 +52,8 @@ public class Store implements Ontology, Plugin {
 	 * <p>
 	 * Configuration keys have the form {@code rdf.baseURI.1}, {@code rdf.file.1}, {@code rdf.format.1}.
 	 * rdf.file is mandatory, other parameters are optional.
+	 * rdf.skosScheme can specify the skos:ConceptScheme to find top concepts and unique notations
+	 *  
 	 * @param conf configuration parameters
 	 * @throws FileNotFoundException if one of the specified files can not be found 
 	 * @throws IOException for i/o exceptions while reading the files
@@ -69,14 +76,42 @@ public class Store implements Ontology, Plugin {
 			i++;
 		}
 		initializeRepo(files.toArray(new File[files.size()]), baseURIs.toArray(new String[baseURIs.size()]));
+		if( conf.containsKey("rdf.skosScheme") ){
+			this.scheme = repo.getValueFactory().createURI(conf.get("rdf.skosScheme")); 
+		}
+	}
+	/**
+	 * Infer inverse relations. 
+	 * The first predicate is searched. For each found statement the inverse predicate is added if it didn't exist previously. 
+	 * @param predicate predicate to search (use the less common one)
+	 * @param inversePredicate inverse predicate to add
+	 * @return number of inferred statements
+	 * @throws RepositoryException error
+	 */
+	protected int inferInverseRelations(URI predicate, URI inversePredicate) throws RepositoryException{
+		RepositoryResult<Statement> res = rc.getStatements(null, predicate, null, false);
+		int count=0;
+		try{
+			while( res.hasNext() ){
+				Statement stmt = res.next();
+				// try to find whether inverse is already existing
+				if( stmt.getObject() instanceof Resource 
+						&& !rc.hasStatement((Resource)stmt.getObject(), inversePredicate, stmt.getSubject(), false) )
+				{
+					rc.add((Resource)stmt.getObject(), inversePredicate, stmt.getSubject(), inferredContext);
+					count ++;
+				}
+			}
+		}finally{
+			res.close();
+		}
+		return count;
 	}
-	
 	private void initializeRepo(File[] files, String[] baseURIs) throws RepositoryException, RDFParseException, IOException{
 	    repo = new SailRepository(new MemoryStore());
 	    repo.initialize();
-
 		rc = repo.getConnection();
-		
+		inferredContext = repo.getValueFactory().createURI("http://sekmi.de/histream/inferredInverse");
 		this.lastModified = 0;
 
 		for( int i=0; i<files.length; i++ ){
@@ -86,16 +121,28 @@ public class Store implements Ontology, Plugin {
 		    
 			// use timestamps from files for last modified date
 			lastModified = Math.max(lastModified, file.lastModified());
-		}		
+		}
+		int inferred = 0;
+	    inferred += inferInverseRelations(SKOS.TOP_CONCEPT_OF, SKOS.HAS_TOP_CONCEPT);
+	    inferred += inferInverseRelations(SKOS.BROADER, SKOS.NARROWER);
+	    inferred += inferInverseRelations(SKOS.NARROWER, SKOS.BROADER);
+	    if( inferred != 0 ){
+	    	log.fine("Inferred "+inferred+" statements.");
+	    }
+	    
 	}
 
 	public Store(File[] files, String[] baseURIs) throws RepositoryException, RDFParseException, IOException{
 		initializeRepo(files, baseURIs);
 	}
 	
+
 	public Store(File file) throws RepositoryException, RDFParseException, IOException{
 		this(new File[]{file}, new String[]{null});
 	}
+	public void setConceptScheme(String schemeURI){
+		this.scheme = repo.getValueFactory().createURI(schemeURI);
+	}
 	
 	public RepositoryConnection getConnection(){return rc;}
 
@@ -120,8 +167,11 @@ public class Store implements Ontology, Plugin {
 		else return concepts.toArray(new Concept[concepts.size()]);
 	}
 	public Concept[] getTopConcepts()throws OntologyException{
-		// TODO use ConceptSchema specified in configuration
-		return getRelatedConcepts(null, SKOS.HAS_TOP_CONCEPT);	
+		// if this.scheme is null, top concepts of all schemes are returned
+		return getRelatedConcepts(this.scheme, SKOS.HAS_TOP_CONCEPT);
+	}
+	public Concept[] getTopConcepts(String schemeURI)throws OntologyException{
+		return getRelatedConcepts(repo.getValueFactory().createURI(schemeURI), SKOS.HAS_TOP_CONCEPT);
 	}
 	private Concept[] getRelatedConcepts(Resource subject, URI predicate)throws OntologyException{
 		RepositoryResult<Statement> rr;

HIStream-SKOS/src/test/java/de/sekmi/histream/ontology/skos/OntologyTest.java

@@ -16,10 +16,12 @@ import de.sekmi.histream.ontology.skos.Store;
 
 public class OntologyTest {
 	Store store;
+	final static String NS_PREFIX="http://sekmi.de/histream/skos/tests#";
 	
 	@Before
 	public void setupOntology()throws Exception{
 		store = new Store(new File("examples/test-ontology.ttl"));
+		store.setConceptScheme(NS_PREFIX+"TestScheme");
 	}
 
 	@Test
@@ -70,6 +72,37 @@ public class OntologyTest {
 		Assert.assertNotNull(narrower);	
 		Assert.assertEquals(4, narrower.length);
 	}
+	
+	@Test
+	public void inferredBroaderTest() throws OntologyException{
+		Concept[] top = store.getTopConcepts();
+		Assert.assertNotNull(top);
+		Assert.assertEquals(1, top.length);
+		
+		Concept[] narrower = top[0].getNarrower();
+		Assert.assertNotNull(narrower);	
+		for( int i=0; i<narrower.length; i++ ){
+			Concept[] broader = narrower[i].getBroader();
+			Assert.assertNotNull(broader);
+			Assert.assertEquals(1, broader.length);
+			Assert.assertEquals(top[0], broader[0]);		
+		}
+	}
+	
+	@Test
+	public void inferredHasTopConceptAndNarrowerTest() throws OntologyException{
+		Concept[] top = store.getTopConcepts(NS_PREFIX+"OtherScheme");
+		Assert.assertNotNull(top);
+		Assert.assertEquals(1, top.length);
+		
+		Concept[] narrower = top[0].getNarrower();
+		Assert.assertNotNull(narrower);
+		Assert.assertEquals(1, narrower.length);
+		String[] ids = narrower[0].getIDs();
+		Assert.assertEquals(1, ids.length);
+		Assert.assertEquals("other", ids[0]);
+	}
+	
 	@Test
 	public void testLanguage() throws OntologyException{
 		Concept c = store.getConceptByNotation("T:type:int");