为什么此 SPARQL 查询 return 某些项目作为主题？

Question

我有如下数据图：

@prefix hr: <http://learningsparql.com/ns/humanResources#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix sch: <http://schema.org/> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

hr:Another a rdfs:Class .

hr:Employee a rdfs:Class ;
    rdfs:label "model" ;
    rdfs:comment "a good employee" .

hr:Longer a hr:Employee ;
    rdfs:label "model" ;
    rdfs:comment "a good employee" .

hr:freestanding a rdf:Property ;
    sch:rangeIncludes sch:Text .

hr:missing rdfs:comment "some comment about missing" .

hr:name a rdf:Property ;
    sch:domainIncludes hr:Employee .

hr:nosuper a rdf:Property ;
    sch:domainIncludes hr:Uncreated ;
    sch:rangeIncludes sch:Text .

hr:randomtype a hr:invalidtype ;
    rdfs:label "some label about randomtype" ;
    rdfs:comment "some comment about randomtype" .

hr:typo a rdfs:Classs ;
    rdfs:label "some label about typo" ;
    rdfs:comment "some comment about typo" .

三元组中定义的唯一主题是 hr:Another、hr:Employee、hr:Longer、hr:freestanding、hr:missing、hr:name、hr:nosuper、hr:randomtype 和 hr:typo。作为证明，当我运行查询时：

SELECT DISTINCT ?s 
WHERE {
    ?s ?p ?o .    
}

我得到结果：

--------------------------------------------------------------
| s                                                          |
==============================================================
| <http://learningsparql.com/ns/humanResources#freestanding> |
| <http://learningsparql.com/ns/humanResources#Another>      |
| <http://learningsparql.com/ns/humanResources#typo>         |
| <http://learningsparql.com/ns/humanResources#nosuper>      |
| <http://learningsparql.com/ns/humanResources#Employee>     |
| <http://learningsparql.com/ns/humanResources#randomtype>   |
| <http://learningsparql.com/ns/humanResources#Longer>       |
| <http://learningsparql.com/ns/humanResources#missing>      |
| <http://learningsparql.com/ns/humanResources#name>         |
--------------------------------------------------------------

但是，如果我执行此 SPARQL 查询：

SELECT DISTINCT ?s
WHERE {
    {

            ?s rdf:type* ?o .    
    }
}

我得到以下结果：

--------------------------------------------------------------
| s                                                          |
==============================================================
| <http://learningsparql.com/ns/humanResources#Longer>       |
| rdfs:Class                                                 |
| sch:Text                                                   |
| "some comment about typo"                                  |
| "some label about typo"                                    |
| <http://learningsparql.com/ns/humanResources#nosuper>      |
| "a good employee"                                          |
| <http://learningsparql.com/ns/humanResources#Uncreated>    |
| <http://learningsparql.com/ns/humanResources#missing>      |
| "some comment about randomtype"                            |
| "model"                                                    |
| <http://learningsparql.com/ns/humanResources#freestanding> |
| "some label about randomtype"                              |
| "some comment about missing"                               |
| <http://learningsparql.com/ns/humanResources#Another>      |
| <http://learningsparql.com/ns/humanResources#invalidtype>  |
| <http://learningsparql.com/ns/humanResources#typo>         |
| <http://learningsparql.com/ns/humanResources#randomtype>   |
| <http://learningsparql.com/ns/humanResources#Employee>     |
| rdfs:Classs                                                |
| rdf:Property                                               |
| <http://learningsparql.com/ns/humanResources#name>         |
--------------------------------------------------------------

我不确定为什么 rdf:Property、"a good employee"、sch:Text 等项目在数据图中不是主题时却作为主题返回。

为什么是他们？

显然，这与 SPARQL 如何处理属性我还不了解的路径有关。

Answer 1

您正在使用带有零个或多个通配符（“*”）的属性路径。实际上，模式 ?s rdf:type* ?o 表示 "every value ?s connected through zero or more type relations to any value ?o"。

图中出现的每个 值（实际上是任何图中的每个值）都与之匹配，因为每个值至少具有零类型关系。因此，会返回像 "some comment about typo" 这样的值，因为尽管它从未作为主题出现在您的数据中，但它确实是一个与其他事物具有零类型关系的值。

为什么此 SPARQL 查询 return 某些项目作为主题？

Why does this SPARQL query return certain items as subjects?

sparql

rdf

turtle-rdf