我在两个单独的查询中计算了有向图中每个节点的indegree和outdegree:
SELECT ?s (COUNT(*) AS ?outdegree)
{ ?s ?p ?o }
GROUP BY ?s
ORDER BY DESC(?outdegree)
SELECT ?o (COUNT(*) AS ?indegree)
{ ?s ?p ?o }
GROUP BY ?o
ORDER BY DESC(?indegree)
我需要计算图表的最大程度。由于有向图的最大度是图的最大值(indegree + outdegree),我想知道如何组合上述两个查询的结果来计算它。
此外,如果有更有效的方法,请同时提出建议。
答案 0 :(得分:3)
使用以下测试数据:
<urn:ex:cent0> <urn:ex:p> <urn:ex:cent1> , <urn:ex:o1> , <urn:ex:o0> .
<urn:ex:s1> <urn:ex:p> <urn:ex:cent0> .
<urn:ex:cent1> <urn:ex:p> <urn:ex:o3> , <urn:ex:o2> .
<urn:ex:s2> <urn:ex:p> <urn:ex:cent0> .
<urn:ex:s0> <urn:ex:p> <urn:ex:cent0> .
我执行了您的查询和以下查询:
SELECT ?cent (( ?indegree + ?outdegree ) AS ?degree)
WHERE
{ { SELECT (?s AS ?cent) (count(*) AS ?outdegree)
WHERE
{ ?s ?p ?o }
GROUP BY ?s
ORDER BY DESC(?outdegree)
}
{ SELECT (?o AS ?cent) (count(*) AS ?indegree)
WHERE
{ ?s ?p ?o }
GROUP BY ?o
ORDER BY DESC(?indegree)
}
}
导致以下输出:
-----------------------------
| o | indegree |
=============================
| <urn:ex:cent0> | 3 |
| <urn:ex:cent1> | 1 |
| <urn:ex:o0> | 1 |
| <urn:ex:o1> | 1 |
| <urn:ex:o2> | 1 |
| <urn:ex:o3> | 1 |
-----------------------------
------------------------------
| s | outdegree |
==============================
| <urn:ex:cent0> | 3 |
| <urn:ex:cent1> | 2 |
| <urn:ex:s0> | 1 |
| <urn:ex:s1> | 1 |
| <urn:ex:s2> | 1 |
------------------------------
---------------------------
| cent | degree |
===========================
| <urn:ex:cent0> | 6 |
| <urn:ex:cent1> | 3 |
---------------------------
这满足了识别具有最大总度的节点的目标。以下是我用来构建此模型并执行此测试的代码(如果您希望重现它):
final Resource c0 = ResourceFactory.createResource("urn:ex:cent0");
final Resource c1 = ResourceFactory.createResource("urn:ex:cent1");
final Property p = ResourceFactory.createProperty("urn:ex:p");
final Model model = new ModelCom(Factory.createDefaultGraph()){{
this.add(this.createResource("urn:ex:s0"), p, c0);
this.add(this.createResource("urn:ex:s1"), p, c0);
this.add(this.createResource("urn:ex:s2"), p, c0);
this.add(c0, p, this.createResource("urn:ex:o0"));
this.add(c0, p, this.createResource("urn:ex:o1"));
this.add(c0, p, c1);
this.add(c1, p, this.createResource("urn:ex:o2"));
this.add(c1, p, this.createResource("urn:ex:o3"));
}};
final Query outdeg = QueryFactory.create(
"SELECT ?s (COUNT(*) AS ?outdegree)\n"+
"{ ?s ?p ?o }\n"+
"GROUP BY ?s\n"+
"ORDER BY DESC(?outdegree)"
);
final Query indeg = QueryFactory.create(
"SELECT ?o (COUNT(*) AS ?indegree)\n"+
"{ ?s ?p ?o }\n"+
"GROUP BY ?o\n"+
"ORDER BY DESC(?indegree)"
);
final Query alldeg = QueryFactory.create(
"SELECT ?cent ((?indegree+?outdegree) AS ?degree) WHERE {\n"+
" {SELECT (?s AS ?cent) (COUNT(*) AS ?outdegree)\n"+
" { ?s ?p ?o }\n"+
" GROUP BY ?s\n"+
" ORDER BY DESC(?outdegree)\n"+
" }\n"+
" {SELECT (?o AS ?cent) (COUNT(*) AS ?indegree)\n"+
" { ?s ?p ?o }\n"+
" GROUP BY ?o\n"+
" ORDER BY DESC(?indegree)\n"+
" }\n"+
"}"
);
@Test
public void test()
{
model.write(System.out, "TTL");
System.out.println();
System.out.println(alldeg);
final QueryExecution exec0 = QueryExecutionFactory.create(indeg, model);
ResultSetFormatter.out(exec0.execSelect(), indeg);
exec0.close();
final QueryExecution exec1 = QueryExecutionFactory.create(outdeg, model);
ResultSetFormatter.out(exec1.execSelect(), outdeg);
exec1.close();
final QueryExecution exec2 = QueryExecutionFactory.create(alldeg, model);
ResultSetFormatter.out(exec2.execSelect(), alldeg);
exec2.close();
}
答案 1 :(得分:3)
您可以使用非常简单的查询来获取每个顶点?x
的度:
select ?x (count(*) as ?degree) {
{ ?x ?p ?o } union
{ ?s ?p ?x }
}
group by ?x
例如,关于这些数据:
@prefix : <https://stackoverflow.com/q/24270532/1281433/> .
# a
# |
# V
# b<--c-->d
# |
# V
# e
:a :p :c .
:c :p :b, :d, :e .
你会得到结果:
---------------
| x | degree |
===============
| :a | 1 |
| :b | 1 |
| :c | 4 |
| :d | 1 |
| :e | 1 |
---------------
现在,如果您想要最大值,您可以简单地订购并使用限制为1,例如
select ?x (count(*) as ?degree) {
{ ?x ?p ?o } union
{ ?s ?p ?x }
}
group by ?x
order by desc(?degree)
limit 1
---------------
| x | degree |
===============
| :c | 4 |
---------------
如果只有一个具有最高学位的顶点,这将有效。如果有多个具有相同的最高学位,您将获得其中一个。
如果您真的希望合并您已经获得的两个查询,那么Rob Hall's answer之类的内容将起作用,除了,因为子查询不是t返回具有0 indegree或0 outdegree的节点,它们不在最终结果中,因为它们不可用于连接。因此,如果您保证每个节点都具有非零的indegrees和outdegree,则只使用该方法。他的答案也很有用,作为如何构建图形并以编程方式使用Jena运行这些查询的示例。