Question

我是RDF和SPARQL的新手，正在为正确的语法而苦苦挣扎。当我在网络上查找示例时，它看起来相当简单，但是当我尝试应用它并进行练习时，它根本不起作用。

当前，我必须制作一个包含三列的列表，其中包含欧盟国家，人口规模（从大到小排列）以及该国拥有的政府类型。

我尝试了许多PREFIX和几乎所有可以想象的文本（请参见下文），但是没有任何效果。

PREFIX dbc: <dbc:Member_states_of_the_European_Union>
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dcterms: <http://purl.org/dc/terms/>
PREFIX schema: <http://schema.org/Country>

SELECT ?populationsize
WHERE
{
?populationsize dbo:populationTotal ?number
}

Answer 1

就我个人而言，这还不是很清楚，但这可行！

PREFIX  dbo:  <http://dbpedia.org/ontology/>
PREFIX  yago: <http://dbpedia.org/class/yago/>
PREFIX  dbp:  <http://dbpedia.org/property/>
PREFIX  dct:  <http://purl.org/dc/terms/>

SELECT DISTINCT  *
WHERE
{ ?country  dct:subject  
<http://dbpedia.org/resource/Category:Member_states_of_the_European_Union> ;
          dbo:populationTotal  ?populationTotal;
          dbo:governmentType  ?governmentType
}

ORDER BY DESC(?populationTotal)

Answer 2

请注意，your revised query未使用，因此您无需包括yago:或dct:前缀。我还为类别添加了另一个前缀。

PREFIX  dbc:  <http://dbpedia.org/resource/Category:>
PREFIX  dbo:  <http://dbpedia.org/ontology/>
PREFIX  dct:  <http://purl.org/dc/terms/>

SELECT DISTINCT  *
WHERE
{ ?country  dct:subject          dbc:Member_states_of_the_European_Union ;
            dbo:populationTotal  ?populationTotal ;
            dbo:governmentType   ?governmentType
}
ORDER BY DESC(?populationTotal)

这是相同的查询，根本没有PREFIX-

SELECT DISTINCT  *
WHERE
{ ?country  http://purl.org/dc/terms/subject             http://dbpedia.org/resource/Category:Member_states_of_the_European_Union ;
            http://dbpedia.org/ontology/populationTotal  ?populationTotal ;
            http://dbpedia.org/ontology/governmentType   ?governmentType
}
ORDER BY DESC(?populationTotal)

所需标签只是当前正在检索的URI的属性。标签以多种语言存在，因此我在此处添加了FILTER，以仅获取标记为英语的标签。

PREFIX  dbc:  <http://dbpedia.org/resource/Category:>
PREFIX  dbo:  <http://dbpedia.org/ontology/>
PREFIX  dct:  <http://purl.org/dc/terms/>

SELECT DISTINCT  *
WHERE
{ ?country  dct:subject          dbc:Member_states_of_the_European_Union ;
            dbo:populationTotal  ?populationTotal ;
            dbo:governmentType   ?governmentType .
  OPTIONAL  { ?country         rdfs:label  ?countryLabel  .
              FILTER ( lang(?countryLabel)="en" ) }
  OPTIONAL  { ?governmentType  rdfs:label  ?governmentTypeLabel  .
              FILTER ( lang(?governmentTypeLabel)="en" ) }
}
ORDER BY DESC(?populationTotal)

我知道您既不希望使用文字类型也不希望使用langtags，所以这里还有一个调整使所有输出变得简单-

PREFIX  dbc:  <http://dbpedia.org/resource/Category:>
PREFIX  dbo:  <http://dbpedia.org/ontology/>
PREFIX  dct:  <http://purl.org/dc/terms/>

SELECT DISTINCT  ( STR(?populationTotal)     AS ?Population )
                 ( STR(?countryLabel)        AS ?Country )
                 ( STR(?governmentTypeLabel) AS ?Government )
WHERE
{ ?country  dct:subject          dbc:Member_states_of_the_European_Union ;
            dbo:populationTotal  ?populationTotal ;
            dbo:governmentType   ?governmentType .
  OPTIONAL  { ?country  rdfs:label  ?countryLabel  .
                FILTER ( LANG(?countryLabel) = "en" ) }
  OPTIONAL  { ?governmentType  rdfs:label  ?governmentTypeLabel  .
                FILTER ( LANG(?governmentTypeLabel) = "en" ) }
}
ORDER BY DESC(?populationTotal)

dbpedia.org的正确语法SPARQL查询

2 个答案: