相同的查询在DBpedia endpoints (http://ko.dbpedia.org/sparql)中有效,但在我的Java代码中不起作用 . 我只是想使用"COUNT"函数提取频率 .
VirtGraph set = new VirtGraph("http://ko.dbpedia.org", HOST, USERNAME, PASSWORD);
Query freqsparql = QueryFactory.create("SELECT ?class count(distinct ?s) as ?count where{?s <http://ko.dbpedia.org/property/이름> ?o. ?s a ?class.} order by DESC(?count)");
VirtuosoQueryExecution freqvqe = VirtuosoQueryExecutionFactory.create(freqsparql, set);
ResultSet freqresults = freqvqe.execSelect();
错误如下 .
Exception in thread "main" com.hp.hpl.jena.query.QueryParseException: Encountered " "count" "count "" at line 1, column 15.
Was expecting one of:
<VAR1> ...
<VAR2> ...
"from" ...
"where" ...
"(" ...
"{" ...
at com.hp.hpl.jena.sparql.lang.ParserSPARQL11.perform(ParserSPARQL11.java:102)
at com.hp.hpl.jena.sparql.lang.ParserSPARQL11.parse$(ParserSPARQL11.java:53)
at com.hp.hpl.jena.sparql.lang.SPARQLParser.parse(SPARQLParser.java:37)
at com.hp.hpl.jena.query.QueryFactory.parse(QueryFactory.java:148)
at com.hp.hpl.jena.query.QueryFactory.create(QueryFactory.java:80)
at com.hp.hpl.jena.query.QueryFactory.create(QueryFactory.java:53)
at com.hp.hpl.jena.query.QueryFactory.create(QueryFactory.java:41)
我正在使用virt_jena2.jar和virtjdbc4.jar . 我已经查看了类似的问题和答案(Jena ARQ扩展和SPARQL 1.1支持这个聚合查询 - 但我找不到如何更改它 - 我认为我正在使用SPARQL1.1,因为错误消息包含PARSERSPARQL11 . java),但是在这一点上无法弄清楚如何解决这个问题 .
提前致谢 .
String sparqlQueryString = "SELECT ?class count(distinct ?s) as ?count where{?s <http://ko.dbpedia.org/property/이름> ?o. ?s a ?class.} order by DESC(?count)";
Query query = QueryFactory.create(sparqlQueryString);
QueryExecution qexec = QueryExecutionFactory.sparqlService(
"http://ko.dbpedia.org/sparql", query);
try {
ResultSet results = qexec.execSelect();
while(results.hasNext()){
QuerySolution freqresult = results.nextSolution();
RDFNode domain = freqresult.get("class");
RDFNode freqcount = freqresult.get("count");
System.out.println(freqresult);
System.out.println(domain + "---" + freqcount);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
qexec.close();
}
这个Jena代码(没有Virtuoso)给了我同样的错误信息 .
2 回答
这是非法的SPARQL语法:
它应该是
您将遇到
?class
的问题:因为它不是一个分组变量(使用
count
你有一组所有东西) . 你的意思是GROUP BY ?class
?关键字是
Encountered " "count" "COUNT ""