Created
October 3, 2012 22:23
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Example of loading ontology imports from named graphs in a local TDB store
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| package example; | |
| import java.io.File; | |
| import java.io.StringReader; | |
| import org.openjena.atlas.lib.NotImplemented; | |
| import com.hp.hpl.jena.ontology.OntModel; | |
| import com.hp.hpl.jena.ontology.OntModelSpec; | |
| import com.hp.hpl.jena.query.Dataset; | |
| import com.hp.hpl.jena.rdf.model.*; | |
| import com.hp.hpl.jena.tdb.TDB; | |
| import com.hp.hpl.jena.tdb.TDBFactory; | |
| import com.hp.hpl.jena.vocabulary.*; | |
| /** | |
| * <p>This Jena example re-uses named graphs stored in a TDB model | |
| * as the imports in an ontology.</p> | |
| * | |
| * @author Ian Dickinson, Epimorphics (mailto:[email protected]) | |
| */ | |
| public class ImportTDBModelsExample | |
| { | |
| /***********************************/ | |
| /* Constants */ | |
| /***********************************/ | |
| public static String ONT1 = "http://example.org/test#ont1"; | |
| public static String ONT2 = "http://example.org/test#ont2"; | |
| // the model we're going to load, which imports ont1 and ont2 | |
| public static String SOURCE = | |
| "@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .\n" + | |
| "@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .\n" + | |
| "@prefix owl: <http://www.w3.org/2002/07/owl#> .\n" + | |
| "<http://example.org/test#upper> a owl:Ontology ;\n" + | |
| " owl:imports <" + ONT1 + "> ;\n" + | |
| " owl:imports <" + ONT2 + "> .\n"; | |
| /***********************************/ | |
| /* Static variables */ | |
| /***********************************/ | |
| /***********************************/ | |
| /* Instance variables */ | |
| /***********************************/ | |
| /***********************************/ | |
| /* Constructors */ | |
| /***********************************/ | |
| /***********************************/ | |
| /* External signature methods */ | |
| /***********************************/ | |
| public static void main( String[] args ) { | |
| new ImportTDBModelsExample().run(); | |
| } | |
| public void run() { | |
| Dataset ds = initialiseTDB(); | |
| loadTDBContent( ds ); | |
| OntModel m = loadImportingOntology( ds.getDefaultModel(), ds ); | |
| m.writeAll( System.out, "Turtle", null ); | |
| } | |
| /***********************************/ | |
| /* Internal implementation methods */ | |
| /***********************************/ | |
| /** | |
| * Initialise the local TDB image if necessary. | |
| */ | |
| protected Dataset initialiseTDB() { | |
| String tdbPath = "./target/data/tdb"; | |
| new File( tdbPath ).mkdirs(); | |
| return TDBFactory.createDataset( tdbPath ); | |
| } | |
| /** | |
| * Load some test content into TDB, unless it has already been initialized. | |
| * @param ds | |
| */ | |
| protected void loadTDBContent( Dataset ds ) { | |
| if (!ds.containsNamedModel( ONT1 )) { | |
| loadExampleGraph( ONT1, ds, "The Dread Pirate Roberts" ); | |
| loadExampleGraph( ONT2, ds, "Chewbacca" ); | |
| } | |
| } | |
| /** | |
| * Create a graph with the given name in the dataset, and initialise it with | |
| * some fake content (namely an owl:Ontology resource). This is a proxy for | |
| * loading a real ontology into the model. | |
| * | |
| * @param graphName | |
| * @param ds | |
| * @param creator | |
| */ | |
| protected void loadExampleGraph( String graphName, Dataset ds, String creator ) { | |
| Model m = ModelFactory.createDefaultModel(); | |
| m.createResource( graphName ) | |
| .addProperty( RDF.type, OWL.Ontology) | |
| .addProperty( DCTerms.creator, creator ); | |
| ds.addNamedModel( graphName, m ); | |
| TDB.sync( m ); | |
| } | |
| /** | |
| * Now we create an ontology model that imports ont1 and ont2, but arrange | |
| * that these are obtained from the TDB image. | |
| * | |
| * @param base | |
| */ | |
| protected OntModel loadImportingOntology( Model base, Dataset ds ) { | |
| // this is a test, so empty the base first just to be sure | |
| base.removeAll(); | |
| OntModelSpec spec = new OntModelSpec( OntModelSpec.OWL_MEM ); | |
| spec.setImportModelGetter( new LocalTDBModelGetter( ds ) ); | |
| OntModel om = ModelFactory.createOntologyModel( spec, base ); | |
| // now read the source model | |
| StringReader in = new StringReader( SOURCE ); | |
| om.read( in, null, "Turtle" ); | |
| return om; | |
| } | |
| /***********************************/ | |
| /* Inner class definitions */ | |
| /***********************************/ | |
| /** | |
| * <p>A type of model getter that loads models from a local TDB instance, | |
| * if they exist as named graphs using the model URI as the graph name.</p> | |
| */ | |
| static class LocalTDBModelGetter implements ModelGetter { | |
| private Dataset ds; | |
| public LocalTDBModelGetter( Dataset dataset ) { | |
| ds = dataset; | |
| } | |
| @Override | |
| public Model getModel( String uri ) { | |
| throw new NotImplemented( "getModel( String ) is not implemented" ); | |
| } | |
| @Override | |
| public Model getModel( String uri, ModelReader loadIfAbsent ) { | |
| Model m = ds.getNamedModel( uri ); | |
| // create the model if necessary. In actual fact, this example code | |
| // will not exercise this code path, since we pre-define the models | |
| // we want to see in TDB | |
| if (m == null) { | |
| m = ModelFactory.createDefaultModel(); | |
| loadIfAbsent.readModel( m, uri ); | |
| ds.addNamedModel( uri, m ); | |
| } | |
| return m; | |
| } | |
| } // LocalTDBModelGetter | |
| } | |
calling ds.close() at the end of run() seems to solve the problem.
org.openjena.atlas.lib.NotImplemented seems to have been deprecated. Import org.apache.jena.atlas.lib.NotImplemented instead.
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I tried out this code with Jena 2.11.0, TDB 1.0.0. The code works the first time through but then if I run it again (repo already exists, models loaded) I get the error below. I guess prefix mappings are required?
Exception in thread "main" java.lang.NullPointerException
at com.hp.hpl.jena.tdb.store.DatasetPrefixesTDB.readPrefixMap(DatasetPrefixesTDB.java:174)
at com.hp.hpl.jena.sparql.graph.GraphPrefixesProjection.getNsPrefixMap(GraphPrefixesProjection.java:62)
at com.hp.hpl.jena.tdb.store.DatasetPrefixesTDB.getPrefixMapping(DatasetPrefixesTDB.java:223)
at com.hp.hpl.jena.tdb.store.DatasetPrefixesTDB.getPrefixMapping(DatasetPrefixesTDB.java:214)
at com.hp.hpl.jena.tdb.store.GraphTDB.createPrefixMapping(GraphTDB.java:75)
at com.hp.hpl.jena.graph.impl.GraphBase.getPrefixMapping(GraphBase.java:186)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.getPrefixMapping(ModelCom.java:959)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.withDefaultMappings(ModelCom.java:1003)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.(ModelCom.java:74)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.(ModelCom.java:70)
at com.hp.hpl.jena.rdf.model.ModelFactory.createModelForGraph(ModelFactory.java:176)
at com.hp.hpl.jena.sparql.core.DatasetImpl.graph2model(DatasetImpl.java:271)
at com.hp.hpl.jena.sparql.core.DatasetImpl.getDefaultModel(DatasetImpl.java:103)
at com.ge.research.sadl.jena.reasoner.ImportTDBModelsExample.run(ImportTDBModelsExample.java:64)
at com.ge.research.sadl.jena.reasoner.ImportTDBModelsExample.main(ImportTDBModelsExample.java:58)