通过联邦SPARQL查询连接Linkedmdb和DBpedia

Question

我运行了以下查询，并从linkedmdb获得了电影及其对应的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。此外，我还需要从DBpedia获取电影的dcterms:subject属性的值。我不能理解如何连接它们？我可以通过SPARQL来完成吗?或者我需要为此编写代码吗？

Answer 1

你想要一个federated SPARQL query。您不需要编写代码(除了SPARQL查询)。您将需要一个支持它们的端点，并且由于它需要查询多个端点，因此您可能需要运行自己的端点(它可能不包含任何实际数据，但可以为您执行联合)。根据您上面概述的需求，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，该查询不执行SELECT ?dbpediaLink，因为您可能对查看该值并不感兴趣，而是希望使用它从DBpedia中检索数据。当然，如果你想要的话，你可以把它加回去。

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

您不能直接对ARQ运行该命令，但是您可以使用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，所以即使我们有一个LIMIT 50，实际上我们得到的不是50部电影，而是50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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