filter - 如何按 BlankNode id 过滤

Question

我正在尝试在 GraphDB 上的 SPARQL playground 中运行此查询。

select * where { 
    ?s content:value ?value .
    FILTER REGEX(str(?value), "_:x1697BD364N0abcdd866d54")
} 

?value 是 BNodes

我正在尝试过滤 BNode ID 为:_:x1697BD364N0abcdd866d54

的所有值

我尝试了几种不同的方法来按 ID 进行过滤:

1. FILTER REGEX(str(?value), "#bnode-id")
2. FILTER (?value), "#bnode-id")

但都没有成功。

问题:

1. 您将如何根据 bnode id 进行过滤？
2. 是否有可能STR(bnode)？

Answer 1

1. How would you filter based on a bnode id label?

See blank-nodes标签信息。简而言之，不能依赖 SPARQL 查询中的空白节点标签:

There need not be any relation between a label _:a in the result set and a blank node in the data graph with the same label.

An application writer should not expect blank node labels in a query to refer to a particular blank node in the data.

如果在SPARQL中难以通过属性等区分空白节点，可以使用GraphDB的内部资源标识符。

PREFIX ent: <http://www.ontotext.com/owlim/entity#>
SELECT * {
    ?s content:value ?value .
    ?s ent:id ?id .
    FILTER (?id = 424242)
}

或

PREFIX ent: <http://www.ontotext.com/owlim/entity#>
SELECT * {
    ?s content:value ?value 
    BIND (ent:id(?s) AS ?id)
    FILTER (?id = 424242)
}

---

2. Is it possible to STR(bnode)?

没有。来自 17.4.2.5 str :

simple literal  STR (literal ltrl)
simple literal  STR (IRI rsrc)

Returns the lexical form of ltrl (a literal); returns the codepoint representation of rsrc (an IRI).