我运行了以下查询，并从linkedmdb获取了电影及其相应的DBpedia URI的数据。
SELECT ?film ?label ?dbpediaLink
WHERE {
?film rdf:type movie:film .
?film rdfs:label ?label .
?film owl:sameAs ?dbpediaLink
FILTER(regex(str(?dbpediaLink), "dbpedia", "i"))
}
LIMIT 100
我想使用?dbpediaLink URI从DBpedia获取这些电影的类别。另外，我需要从DBpedia获取电影的dcterms:subject属性的值。我无法理解如何连接它们？我可以通过SPARQL来完成，还是需要为此编写代码？
答案 0 :(得分：5)
你想要一个federated SPARQL query。您不需要编写代码（SPARQL查询除外）。您需要一个支持它们的端点，并且由于它需要查询多个端点，您可能需要运行自己的端点（可能不包含任何实际数据，但可以为您执行联合）。根据您在上面概述的要求，您可能需要如下查询。请注意，我从投影变量中删除了?dbpediaLink;也就是说，此查询不会SELECT ?dbpediaLink，因为您可能不会对使用它从DBpedia检索数据看到这个值感兴趣。当然，如果需要，可以将其添加回来。
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX movie: <http://data.linkedmdb.org/resource/movie/>
PREFIX dcterms: <http://purl.org/dc/terms/>
SELECT ?film ?label ?subject WHERE {
SERVICE <http://data.linkedmdb.org/sparql> {
?film a movie:film .
?film rdfs:label ?label .
?film owl:sameAs ?dbpediaLink
FILTER(regex(str(?dbpediaLink), "dbpedia", "i"))
}
SERVICE <http://dbpedia.org/sparql> {
?dbpediaLink dcterms:subject ?subject
}
}
LIMIT 50
您不能直接针对DBpedia SPARQL endpoint运行它，但您可以使用Jena's ARQ在本地运行查询，ARQ将为您执行对其他端点的查询。我创建了一个空文件data.n3作为--query参数传递给ARQ，并且能够像这样运行查询（其中query.sparql是上面的查询）：
$ arq --query query.sparql --data data.n3
结果如下所示。请注意，每个DBpedia资源都可以通过dcterms:subject属性与多个类别相关联，因此即使我们在那里有一个LIMIT 50，我们实际上并没有获得五十部电影，而是五十个结果行。
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| film | label | subject |
================================================================================================================================================================================
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:1960s_horror_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Films_directed_by_Jun_Fukuda> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Giant_monster_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Monster_movies> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:1966_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Godzilla_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Japanese_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Kaiju_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Mothra> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Terrorism_in_fiction> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:1960s_science_fiction_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Sequel_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Japanese-language_films> |
| <http://data.linkedmdb.org/resource/film/11> | "Godzilla vs. the Sea Monster" | <http://dbpedia.org/resource/Category:Mystery_Science_Theater_3000_episodes> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:1930s_musical_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:American_musical_comedy_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:American_romantic_comedy_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:American_romantic_musical_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:1935_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:American_screwball_comedy_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:Black-and-white_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:Films_directed_by_Mark_Sandrich> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:1930s_romantic_comedy_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:United_States_National_Film_Registry_films> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:Films_set_in_London> |
| <http://data.linkedmdb.org/resource/film/105> | "Top Hat" | <http://dbpedia.org/resource/Category:RKO_Pictures_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:American_children's_fantasy_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Best_Original_Music_Score_Academy_Award_winners> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:E.T._the_Extra-Terrestrial> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:English-language_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:1980s_science_fiction_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:1982_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Alien_visitation_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Amblin_Entertainment_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Films_directed_by_Steven_Spielberg> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:1985_novels> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:American_science_fiction_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Films_produced_by_Steven_Spielberg> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Films_set_in_the_San_Fernando_Valley> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Films_that_won_the_Best_Sound_Mixing_Academy_Award> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:United_States_National_Film_Registry_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Universal_Pictures_films> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Best_Drama_Picture_Golden_Globe_winners> |
| <http://data.linkedmdb.org/resource/film/154> | "E.T. the Extra-Terrestrial" | <http://dbpedia.org/resource/Category:Films_that_won_the_Best_Visual_Effects_Academy_Award> |
| <http://data.linkedmdb.org/resource/film/155> | "Easy Rider" | <http://dbpedia.org/resource/Category:1960s_drama_films> |
| <http://data.linkedmdb.org/resource/film/155> | "Easy Rider" | <http://dbpedia.org/resource/Category:American_films> |
| <http://data.linkedmdb.org/resource/film/155> | "Easy Rider" | <http://dbpedia.org/resource/Category:1969_films> |
| <http://data.linkedmdb.org/resource/film/155> | "Easy Rider" | <http://dbpedia.org/resource/Category:Films_shot_in_New_Orleans,_Louisiana> |
| <http://data.linkedmdb.org/resource/film/155> | "Easy Rider" | <http://dbpedia.org/resource/Category:Directorial_debut_films> |
| <http://data.linkedmdb.org/resource/film/155> | "Easy Rider" | <http://dbpedia.org/resource/Category:Films_about_drugs> |
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