Jena Sparql 和构建
CONSTRUCT 是 SELECT 的替代 SPARQL 结果子句。 CONSTRUCT 返回一个 RDF 图，而不是返回结果值表。例如，在以下 Java 代码中运行此查询会产生 HttpException: 406 Unacceptable。但如果我选择 SELECT ?x 而不是 CONSTRUCT 块，那就没问题了。 Jena 是否支持 CONSTRUCT？如果支持，如何支持？ DBpedia 端点可接受这两个查询。
PREFIX : <http://dbpedia.org/resource/>
PREFIX onto: <http://dbpedia.org/ontology/>
CONSTRUCT {
:France onto:anthem ?x
}
WHERE
{
:France onto:anthem ?x .
}
Query query = QueryFactory.create("the query goes here");
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
ResultSet results = qexec.execSelect();
ResultSetFormatter.out(System.out, results, query);
CONSTRUCT is an alternative SPARQL result clause to SELECT. Instead of returning a table of result values, CONSTRUCT returns an RDF graph. For instance, running this query in the following Java code produces an HttpException: 406 Unacceptable. But if instead of the CONSTRUCT block, I choose SELECT ?x, it's just fine. Does Jena support CONSTRUCT, and if so, how? Both queries are acceptable to the DBpedia endpoint.
PREFIX : <http://dbpedia.org/resource/>
PREFIX onto: <http://dbpedia.org/ontology/>
CONSTRUCT {
:France onto:anthem ?x
}
WHERE
{
:France onto:anthem ?x .
}
Query query = QueryFactory.create("the query goes here");
QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);
ResultSet results = qexec.execSelect();
ResultSetFormatter.out(System.out, results, query);
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Jena 支持
CONSTRUCT，但要获取结果，您需要调用不同的方法，因为execSelect和ResultSet仅适用于SELECT< /code> 查询。请使用它：Model是 Jena 用于访问 RDF 图的接口，请参阅 javadocs 了解详细信息。Jena supports
CONSTRUCT, but to get the result you need to call a different method, becauseexecSelectandResultSetare only forSELECTqueries. Use this instead:Modelis Jena's interface for accessing RDF graphs, see the javadocs for details.ResultSetFormatter.out(System.out, results, query) 找不到符号和标识符此时发生预期错误
ResultSetFormatter.out(System.out, results, query) cannot find symbol and identifier expected error occurs at this point