Good points. The code I had was sufficient for my immediate purposes, but for more general and production cases, I'll use your recommendations.
-----Original Message----- From: Ian Dickinson [mailto:[email protected]] Sent: Wednesday, May 08, 2013 4:45 AM To: [email protected] Subject: Re: Query declared properties returns too much On 07/05/13 21:05, David Jordan wrote: > > I ran into this same problem two weeks ago. Joshua Taylor provided me > with an answer, which I have included below. I ended up writing code > similar to the following, where I passed a Resource object > (OntModel.getResource(classURI)) representing the class to the method. > > private long listProperties(Resource resource){ > StmtIterator iter = omodel.listStatements(resource, (Property)null, > (RDFNode)null); > while( iter.hasNext() ){ > Statement stmt = iter.next(); > Property property = stmt.getPredicate(); > String pname = property.getLocalName(); > } > } This solves a completely different problem to listDeclaredProperties(). What this code does is to list the triples in the graph whose subject is the class resource itself. This is not the same as finding the properties that you would normally expect to be associated with an *instance* of the class. An example to clarify: @prefix ex: <http://example.org/example#>. ex:Dog rdf:type owl:Class ; rdfs:comment "The class of all dogs". ex:pedigree rdf:type owl:DatatypeProperty ; rdfs:domain ex:Dog ; rdfs:range xsd:boolean ; rdfs:comment "Denotes whether a particular dog is a pedigree or not" . In this case, the method you provide will return two values, "type" (short for rdf:type) and "comment" (short for rdfs:comment), because those are the only properties *of the class resource itself*. Conversely, listDeclaredProperties() will return ex:pedigree, because that's a property that we would expect to find (note: not are guaranteed to find, this is a rather informal contract) on instances of ex:Dog. For example: ex:fido rdf:type ex:Dog ; ex:pedigree "false"^^xsd:boolean ; rdfs:comment "Fido is a lovable mongrel!". By the way, the method you wrote is almost exactly the listProperties() method of OntClass (as inherited from Resource), except that your version reduces the URI's to local names. Which, incidentally, isn't generally a very good idea. Different predicates have different semantics, and the full URI is necessary to distinguish predicates that might otherwise have the same name. If you need a short name to present a property in a UI, it's much better to use the rdfs:label or skos:prefLabel. Ian
