SPARQL：select 项并计算其标签的出现次数

Question

我已 this SPARQL query 转到开放研究知识图谱 (ORKG)：

PREFIX orkgr: <http://orkg.org/orkg/resource/>
PREFIX orkgc: <http://orkg.org/orkg/class/>
PREFIX orkgp: <http://orkg.org/orkg/predicate/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?o1Label (COUNT(?o1Label) AS ?o1LabelCount)
WHERE {
  ?o1 a orkgc:Paper.
  ?o1 rdfs:label ?o1Label.
  
  FILTER (strlen(?o1Label) > 1).
}

GROUP BY ?o1Label
ORDER BY DESC(?o1LabelCount)

这导致标签 (?o1Label) 和该标签的出现次数 (?o1LabelCount)。

如何扩展此查询以包含实际项目 (?o1) 的列？

因为可能有多个候选项（当 o1LabelCount > 1 时），所以这些项目中的每一项都应该有一行（具有相同的标签和相同的标签计数）。

Answer 1

我看到两个选项：

首先（可能更好）是使用 GROUP_CONCAT and collect the entities into one field to be parsed again on application side. this could look like this (link):

PREFIX orkgr: <http://orkg.org/orkg/resource/>
PREFIX orkgc: <http://orkg.org/orkg/class/>
PREFIX orkgp: <http://orkg.org/orkg/predicate/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?o1Label (GROUP_CONCAT(?o1, "\t") AS ?o1s) (COUNT(?o1Label) AS ?o1LabelCount)
WHERE {
  ?o1 a orkgc:Paper.
  ?o1 rdfs:label ?o1Label.
  
  FILTER (strlen(?o1Label) > 1).
}

GROUP BY ?o1Label
ORDER BY DESC(?o1LabelCount)

另一种方法是使用 nested queries and receive a result as you described (link):

PREFIX orkgr: <http://orkg.org/orkg/resource/>
PREFIX orkgc: <http://orkg.org/orkg/class/>
PREFIX orkgp: <http://orkg.org/orkg/predicate/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?o1Label ?o1 ?o1LabelCount
WHERE {
  ?o1 rdfs:label ?o1Label .

  {
    SELECT ?o1Label (COUNT(?o1Label) AS ?o1LabelCount)
    WHERE {
      [
        a orkgc:Paper;
        rdfs:label ?o1Label
      ]
      FILTER (strlen(?o1Label) > 1).
    }
  }
}

GROUP BY ?o1Label
ORDER BY DESC(?o1LabelCount)

SPARQL：select 项并计算其标签的出现次数

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