yes SPARQL is indeed possible. But in that case, I'd go the SPARQL 1.1 way:
|SELECT DISTINCT ?s||
||WHERE||
|| { ?s a owl:Class||
|| FILTER ( ! isBlank(?s) )||
|| FILTER ( ?s NOT IN (owl:Thing, owl:Nothing) )||
|| FILTER NOT EXISTS { ?s rdfs:subClassOf ?super||
|| FILTER ( ( ?super NOT IN (rdfs:Resource,
owl:Thing, rdfs:Class) ) && ( ?s != ?super ) )||
|| }||
|| }|
On 06.09.19 03:47, Alex To wrote:
> Thanks Lorenz
>
> I figured out the union thing too so I ended up using the below SPARQL
> instead and it seems to work fine but would love to know what is the
> equivalent using Jena API
>
> "SELECT DISTINCT ?s WHERE { " +
> "?s a owl:Class . " +
> "FILTER (!isBlank(?s)) " +
> "FILTER (?s != owl:Thing && ?s != owl:Nothing) . " +
> "OPTIONAL { " +
> " ?s rdfs:subClassOf ?super . " +
> " FILTER (?super != rdfs:Resource && ?super != owl:Thing
> && ?s != ?super) " +
> " } . " +
> "FILTER (!bound(?super))" +
> "}");
>
>
> Regards
>
>
> On Thu, Sep 5, 2019 at 8:00 PM Lorenz Buehmann <
> [email protected]> wrote:
>
>> schema.org contains a bunch of anonymous classes like the union of other
>> classes which are used as domain or range of a property, that's why you
>> get null values because they do not have a URI. If you'd just call
>>
>> |System.out.println(clazz);|
>>
>>
>> you'd see the blank node Ids.
>>
>>
>> Among all those blank nodes, there is indeed the one top level class
>> http://schema.org/Thing .
>>
>>
>> I thought just adding a filter on the iterator is enough, i.e.
>>
>> |topClazzez = topClazzez.filterDrop(OntResource::isAnon);|
>>
>>
>> but while it doesn't return the blank nodes anymore, it leads to an
>> exception:
>>
>>
>> |Exception in thread "main"
>> org.apache.jena.ontology.ConversionException: Cannot convert node
>> http://www.w3.org/2000/01/rdf-schema#Class to OntClass: it does not have
>> rdf:type owl:Class or equivalent||
>> || at
>> org.apache.jena.ontology.impl.OntClassImpl$1.wrap(OntClassImpl.java:82)||
>> || at org.apache.jena.enhanced.EnhNode.convertTo(EnhNode.java:152)||
>> || at org.apache.jena.enhanced.EnhNode.convertTo(EnhNode.java:31)||
>> || at
>> org.apache.jena.enhanced.Polymorphic.asInternal(Polymorphic.java:62)||
>> || at org.apache.jena.enhanced.EnhNode.as(EnhNode.java:107)||
>> || at
>>
>> org.apache.jena.ontology.impl.OntResourceImpl.lambda$listDirectPropertyValues$8(OntResourceImpl.java:1536)||
>> || at
>> org.apache.jena.util.iterator.Map1Iterator.next(Map1Iterator.java:46)||
>> || at
>>
>> org.apache.jena.ontology.impl.OntResourceImpl.computeDirectValues(OntResourceImpl.java:1580)||
>> || at
>>
>> org.apache.jena.ontology.impl.OntResourceImpl.listDirectPropertyValues(OntResourceImpl.java:1553)||
>> || at
>>
>> org.apache.jena.ontology.impl.OntClassImpl.listSuperClasses(OntClassImpl.java:180)||
>> || at
>>
>> org.apache.jena.ontology.impl.OntClassImpl.isHierarchyRoot(OntClassImpl.java:739)||
>> || at
>>
>> org.apache.jena.util.iterator.FilterIterator.hasNext(FilterIterator.java:56)||
>> || at
>>
>> org.apache.jena.util.iterator.WrappedIterator.hasNext(WrappedIterator.java:90)||
>> || at
>>
>> org.apache.jena.util.iterator.FilterIterator.hasNext(FilterIterator.java:55)||
>> || at com.company.Main.main(Main.java:25)|
>>
>>
>>
>> On 05.09.19 03:11, Alex To wrote:
>>> Hi I am trying to load schema.org ontology and get all top classes
>>> using ontModel.listHierarchyRootClasses() but can't get the expected
>>> results with different OntModelSpec.
>>>
>>> If I use OWL_MEM, it lists 2500+ records with all the records have "null"
>>> URI.
>>> If I use OWL_DL_MEM, it lists 0 records
>>>
>>> The code is very simple as follows
>>>
>>> Model model = ModelFactory.createDefaultModel();
>>> model.read("https://schema.org/docs/schemaorg.owl";);
>>> OntModel ontModel =
>>> ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM, model);
>>> ExtendedIterator<OntClass> topClazzez =
>> ontModel.listHierarchyRootClasses();
>>> while (topClazzez.hasNext()) {
>>> OntClass clazz = topClazzez.next();
>>> System.out.println(clazz.getURI());
>>> }
>>>
>>> A minimal Maven project ready to run to demonstrate my problem is here
>>> https://github.com/AlexTo/jena-lab (have a look at the Main.java)
>>>
>>> Thanks a lot
>
> --
>
