java - Sparql 关系请求

Question

嘿，我为 pizzas 制作了门徒教程。我有一份猫头鹰文件。我将该文件保存为 RDF/XML 格式。现在我尝试获取有关文件中数据的一些信息。诸如此类:

"Select * where {
?s rdfs:subClassOf owl:Thing
}

工作。现在我想获取与“hasTopping”相关的所有主题和对象。

OntModel m = ModelFactory.createOntologyModel(OWL_MEM);

    InputStream in = FileManager.get().open("pizza1.owl");
    m.read(in, "RDF/XML");
    String queryString =
                    "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> " +
                    "PREFIX : <http://www.pizza.com/ontologies/pizza.owl> " +
                    "PREFIX owl: <http://www.w3.org/2002/07/owl#>" +
                    "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>" +
                    "PREFIX xml: <http://www.w3.org/XML/1998/namespace>" +
                    "SELECT * WHERE" +
                    "{" +
                    "?s :hasTopping ?o" +
                    "}";
    Query query = QueryFactory.create(queryString);
    QueryExecution qexec = QueryExecutionFactory.create(query,m);
    try {
        ResultSet results = qexec.execSelect();
        while( results.hasNext()) {
            QuerySolution soln = results.nextSolution();
            RDFNode name = soln.get("s");
            RDFNode name1 = soln.get("o");


            //RDFNode name2 = soln.get("s");
            System.out.println("Subject:" + name);
            System.out.println("Object:" + name1);

            //System.out.println(name2);
        }
    } finally {
        qexec.close();
    }

但结果始终为空。希望有人能帮助我。

亲切的问候!

Answer 1

: 的前缀声明缺少 # 或 / 等分隔符 - 取决于它在本体中的定义方式。

如果没有它，使用 :hasTopping 会生成 URI http://www.pizza.com/ontologies/pizza.owlhasTopping