SPARQL应用实例

注1：以下所有代码块均可直接在https://dbpedia.org/sparql中运行。
注2：SPARQL对大小写不敏感。
前缀汇总：

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX owl: <http://www.w3.org/2002/07/owl#>  
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

查询满足条件的三元组数量。

select count(*) as ?total_num
where {?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?name.
}

查询DBpedia中Class数量。

SELECT COUNT(DISTINCT ?class_name) AS ?total_num
WHERE {?class_name rdf:type owl:Class
}

查询所有存在的Class。

SELECT *
WHERE {?class_name rdf:type owl:Class
}

查询所有存在实体的Class类别。

SELECT (COUNT(DISTINCT ?Class_name) AS ?Class_num)
WHERE {?Class_name rdf:type owl:Class.?entity_name rdf:type ?Class_name.
}

查询所有存在实体的主类（rdf:type为owl:Thing）。

SELECT ?main_class (COUNT(DISTINCT ?entity_name) AS ?entity_num)
WHERE{?main_class rdf:type owl:Class.?main_class rdfs:subClassOf owl:Thing.?entity_name rdf:type ?main_class.
}
GROUP BY ?main_class
ORDER BY desc (?entity_num)

查询每个Class及其实体数量并按照实体数量降序排序（此查询返回的Class类别不包括不含有实体的Class类别）。

SELECT ?Class_name (COUNT(?entity_name) AS ?entity_num)
WHERE {?Class_name rdf:type owl:Class.?entity_name rdf:type ?Class_name.
}
GROUP BY ?Class_name
ORDER BY desc (?entity_num)

查询Work类中的实体数量。

SELECT *
WHERE {?entity_name rdf:type dbo:Work.
}

或（其余前缀均可按照类似方式使用。）

SELECT COUNT(DISTINCT ?entity_name)
WHERE {?entity_name rdf:type <http://dbpedia.org/ontology/Work>.
}

查询Work类中具备英文摘要的实体数量。

SELECT COUNT(DISTINCT ?entity_name)
WHERE {?entity_name rdf:type <http://dbpedia.org/ontology/Work>.?entity_name dbo:abstract ?abstract.FILTER(LANGMATCHES(LANG(?abstract), "en"))
}

查询Work类中不具备英文摘要的实体数量（注意语言匹配中用"en"或"EN"均可）。

SELECT COUNT(DISTINCT ?entity_name)
WHERE {?entity_name rdf:type <http://dbpedia.org/ontology/Work>.OPTIONAL{?entity_name dbo:abstract ?abstract.FILTER(LANGMATCHES(LANG(?abstract), "en"))}FILTER(!bound(?abstract))
}

查询每个Class中具有英文摘要的实体数量（此查询所需时间较长，建议将SPARQL嵌入代码，每次查询仅对一个Class执行）。

SELECT ?Class_name (COUNT(DISTINCT ?entity_name) AS ?entity_num_with_en_abstract)
WHERE {?Class_name rdf:type owl:Class.?entity_name rdf:type ?Class_name.?entity_name dbo:abstract ?abstract.FILTER(LANGMATCHES(LANG(?abstract), "en"))
}
GROUP BY ?Class_name
ORDER BY desc (?entity_num_with_en_abstract)

综合应用实例

from SPARQLWrapper import SPARQLWrapper, JSON
import json
sparql = SPARQLWrapper("http://dbpedia.org/sparql")
sparql.setQuery("""SELECT ?main_class (COUNT(DISTINCT ?entity_name) AS ?entity_num)WHERE{?main_class rdf:type owl:Class.?main_class rdfs:subClassOf owl:Thing.?entity_name rdf:type ?main_class.}GROUP BY ?main_classORDER BY desc (?entity_num)
""")
sparql.setReturnFormat(JSON)
sparql.setTimeout(9223372036)
results = sparql.query().convert()
class_dict = {}
for result in results["results"]["bindings"]:if 'http://dbpedia.org/ontology/' in result['main_class']['value']:class_dict[result['main_class']['value']] = -1
f = open('/home/njucs/Desktop/class_dict_keys.txt', 'w')
for item in class_dict.keys():print(item.ljust(50))print(item.ljust(50), file = f)
f.close()
f = open('/home/njucs/Desktop/class_dict.txt', 'w')
seq = 0
for key in class_dict.keys():sparql = SPARQLWrapper("http://dbpedia.org/sparql")sparql.setQuery("""SELECT (COUNT(DISTINCT ?entity_name) AS ?num)WHERE {?entity_name rdf:type <""" + '{0}'.format(key) + """>.?entity_name dbo:abstract ?abstract.FILTER(LANGMATCHES(LANG(?abstract), "en"))}""")sparql.setReturnFormat(JSON)sparql.setTimeout(9223372036)results = sparql.query().convert()class_dict[key] = int(results["results"]["bindings"][0]["num"]["value"])seq += 1print(seq, "\t", key.ljust(50), class_dict[key])print(key, class_dict[key], file=f)
f.close()
json_str = json.dumps(class_dict)
f = open('/home/njucs/Desktop/class_dict.json', 'w')
f.write(json_str)
f.close()
keys = list(class_dict.keys())
values = list(class_dict.values())
ordered_list = list(zip(keys, values))
ordered_list = sorted(ordered_list, key = (lambda x:x[1]), reverse = True)
json_str = json.dumps(ordered_list)
f = open('/home/njucs/Desktop/ordered_list.json', 'w')
f.write(json_str)
f.close()

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