I am new in the field of JENA,so don't laugh at me about this question,please. My question is about the blank node,since I have no idea how to treat them. When I list the root class of a OWL file,there are a lot of blank nodes,even more than the class with URI.Such as
http://xmlns.com/wordnet/1.6/Agent-3 -51cb51a0:134b85abd5d:-7fd3 -51cb51a0:134b85abd5d:-7fc1 -51cb51a0:134b85abd5d:-7fc4 -51cb51a0:134b85abd5d:-7fc7 -51cb51a0:134b85abd5d:-7fca -51cb51a0:134b85abd5d:-7fcc -51cb51a0:134b85abd5d:-7fce -51cb51a0:134b85abd5d:-7fd1 1.the first question is that why there are so many blank nodes created as root class and what's the usage of them? then,when I list the statements of the file,I found there are also many statements with blank node ,for example: class: -51cb51a0:134b85abd5d:-7fcc [-51cb51a0:134b85abd5d:-7fcc, http://www.w3.org/2002/07/owl#minCardinality, "1"^^http://www.w3.org/2001/XMLSchema#nonNegativeInteger] [-51cb51a0:134b85abd5d:-7fcc, http://www.w3.org/2002/07/owl#onProperty, http://www.mindswap.org/2004/owl/funding#source] [-51cb51a0:134b85abd5d:-7fcc, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2002/07/owl#Restriction] class:-51cb51a0:134b85abd5d:-7fce [-51cb51a0:134b85abd5d:-7fce, http://www.w3.org/2002/07/owl#someValuesFrom, http://www.mindswap.org/2004/owl/funding#Funding] [-51cb51a0:134b85abd5d:-7fce, http://www.w3.org/2002/07/owl#onProperty, http://www.mindswap.org/2004/owl/funding#fundedBy] [-51cb51a0:134b85abd5d:-7fce, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2002/07/owl#Restriction] 2.the second question is that why do these blank nodes exist? I can't find them in the Protégé gragh ,but only see them when I parse the file with JENA. Another situation is that when you list all the statements of a class which have URI, some statements are very similar,since the subject and predicate of the statement are same while one object is a resource with URI and another is a blank node.for example the statements for class http://www.owl-ontologies.com/animal.owl#Giraffe is three [http://www.owl-ontologies.com/animal.owl#Giraffe, http://www.w3.org/2000/01/rdf-schema#subClassOf, 72947f0e:134b7e616e0:-7ff9] [http://www.owl-ontologies.com/animal.owl#Giraffe, http://www.w3.org/2000/01/rdf-schema#subClassOf, http://www.owl-ontologies.com/animal.owl#Herbivore] [http://www.owl-ontologies.com/animal.owl#Giraffe, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2002/07/owl#Class] 3.the third question is that is the blank node( 72947f0e:134b7e616e0:-7ff9 ) here a complement or equal class of http://www.owl-ontologies.com/animal.owl#Herbivore.If it is ,why to created a blank node ? Because I want to receate a model with part of the information from another model,so I list all the statements and add them to the new CreatedModel.But I don't know how to deal with the ones with blank node.If I ignore them,that't OK.the new model have no problems.But I add the ones with blank node,there are always display errors.such as Exception in thread "main" com.hp.hpl.jena.ontology.ConversionException: Cannot convert node 2761081c:134b875e25b:-7ffb to OntClass: it does not have rdf:type owl:Class or equivalent at com.hp.hpl.jena.ontology.impl.OntClassImpl$1.wrap(OntClassImpl.java:82) at com.hp.hpl.jena.enhanced.EnhNode.convertTo(EnhNode.java:142) at com.hp.hpl.jena.enhanced.EnhNode.convertTo(EnhNode.java:22) at com.hp.hpl.jena.enhanced.Polymorphic.asInternal(Polymorphic.java:54) at com.hp.hpl.jena.enhanced.EnhNode.as(EnhNode.java:97) at com.hp.hpl.jena.ontology.impl.OntResourceImpl$ObjectAsMapper.map1(OntResourceImpl.java:1607) at com.hp.hpl.jena.ontology.impl.OntResourceImpl$ObjectAsMapper.map1(OntResourceImpl.java:1601) at com.hp.hpl.jena.util.iterator.Map1Iterator.next(Map1Iterator.java:35) at com.hp.hpl.jena.ontology.impl.OntResourceImpl.computeDirectValues(OntResourceImpl.java:1493) at com.hp.hpl.jena.ontology.impl.OntResourceImpl.listDirectPropertyValues(OntResourceImpl.java:1466) at com.hp.hpl.jena.ontology.impl.OntClassImpl.listSuperClasses(OntClassImpl.java:195) at com.hp.hpl.jena.ontology.impl.OntClassImpl.isHierarchyRoot(OntClassImpl.java:722) at com.hp.hpl.jena.ontology.impl.OntModelImpl$1.accept(OntModelImpl.java:527) at com.hp.hpl.jena.ontology.impl.OntModelImpl$1.accept(OntModelImpl.java:524) at com.hp.hpl.jena.util.iterator.FilterKeepIterator.accept(FilterKeepIterator.java:22) at com.hp.hpl.jena.util.iterator.FilterIterator.hasNext(FilterIterator.java:44) But when I add all the namespace of another model to the new one and want to create a blank node with given name then add it to the model to solve it,it doesn't work.My method is that Resource s = CreatedModel.createResource(" http://www.owl-ontologies.com/animal.owl#Herbivore";); Property p = CreatedModel.createProperty(" http://www.w3.org/2000/01/rdf-schema#subClassOf";); Resource o = CreatedModel.createResource(new AnonId("72947f0e:134b7e616e0:-7ff8")); CreatedModel.add(s,p,o); After this process, when I list the statement of the CreatedModel, the new created blank node is not 72947f0e:134b7e616e0:-7ff8, but a random one. 4.So the last question is that could I ignore the statements with blank node when I recreate a new model , will this affect the result ?Or how to create and add a new created blank node with given name to the model? I am very graceful for who can help! Best Wishes!
