java - 从 RDF 节点拉出字符串

Question

在 Jena 中使用 SPARQL 查询时，我试图以更易读的格式获取数据，但是我不知道如何以正确的方式提取数据。就目前而言，输出是:

"http://www.w3.org/TR/2003/PR-owl-guide-20031209/wine#SaucelitoCanyon "

只想将“SaucelitoCanyon”作为输出。

public JenaQuery() {

    String wineRegion = "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>\n"
            + "PREFIX owl: <http://www.w3.org/2002/07/owl#>\n"
            + "PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>\n"
            + "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>\n"
            + "PREFIX wine:<http://www.w3.org/TR/2003/PR-owl-guide-20031209/wine#>\n"
            + "SELECT  ?region ?winery \n"
            + "WHERE {?wine wine:locatedIn ?region . \n"
            + "?region wine:locatedIn wine:CaliforniaRegion  . \n"
            + "?wine wine:hasMaker  ?winery}";

    String inputFileName = "wine.rdf";
    // create an empty model

    Model model = ModelFactory.createDefaultModel();
    // use the FileManager to find the input file
    InputStream in;
    in = FileManager.get().open(inputFileName);
    if (in == null) {
        throw new IllegalArgumentException(
                "File: " + inputFileName + " not found");
    }
    // read the RDF/XML file
    model.read(in, null);
    try (QueryExecution qexec = QueryExecutionFactory.create(wineRegion, model)) {

        ResultSet results = qexec.execSelect();

        while (results.hasNext()) {
            QuerySolution row = results.next();
            RDFNode winery = row.get("winery");
            System.out.println(winery);
        }

        qexec.close();

    }

}

Answer 1

由于您已经在 SPARQL 查询中获得了前缀，因此您可以使用 strafter 和 str 函数将 URI 转换为字符串，并在后面加上后缀字首。在下面，我使用 values ?winery { ... } 将 ?winery 绑定(bind)到特定的 URI，但您的查询已经处理了这个问题。重要的部分是之后的绑定(bind)，它负责字符串处理。

PREFIX wine: <http://www.w3.org/TR/2003/PR-owl-guide-20031209/wine#>
SELECT ?winery ?localname
WHERE {
  values ?winery { wine:SomeWinery }
  bind( strafter(str(?winery),str(wine:)) as ?localname )
}

winery                                                            localname
<http://www.w3.org/TR/2003/PR-owl-guide-20031209/wine#SomeWinery> "SomeWinery"

也就是说，在结构良好的本体中，个人通常会有一个 rdfs:label 来为个人提供字符串标签。当它可用时，您可能会考虑简单地检索该值。例如，

SELECT ?winery ?name
WHERE {
  #-- ... 
  ?winery rdfs:label ?name
}

这之前已在 my answer 中描述过至retrieving the class name of a specific subclass in owl ，但该问题不涉及 Jena，因此它并不完全重复，即使相同的基于 SPARQL 的解决方案也有效。