RDF中的三重复制,权威观点？

Question

如果三重商店包含两倍于相同的三元组,那么(如果存在的话)关于此冗余的权威位置是什么？

另外,是否允许三元组在同一上下文中存储两次相同的三元组？

我问这个是因为在rdflib显然你可以存储两次(或更多)相同的三倍.这是读者

import rdflib
from rdflib import store

s = rdflib.plugin.get('MySQL', store.Store)('rdfstore')

config_string = "host=localhost,password=foo,user=foo,db=foo"
rt = s.open(config_string,create=False)
if rt != store.VALID_STORE:
    s.open(config_string,create=True)

graph = rdflib.ConjunctiveGraph(s, identifier = rdflib.URIRef("urn:uuid:a19f9b78-cc43-4866-b9a1-4b009fe91f52"))
rows = graph.query("SELECT ?id ?value { ?id <http://localhost#ha> ?value . }")
for r in rows:
    print r[0], r[1]

这是作家

import rdflib
from rdflib import store

s = rdflib.plugin.get('MySQL', store.Store)('rdfstore')

config_string = "host=localhost,password=foo,user=foo,db=foo"
rt = s.open(config_string,create=False)
if rt != store.VALID_STORE:
    s.open(config_string,create=True)

graph = rdflib.ConjunctiveGraph(s, identifier = rdflib.URIRef("urn:uuid:a19f9b78-cc43-4866-b9a1-4b009fe91f52"))
graph.add( ( rdflib.URIRef("http://localhost/1000"), rdflib.URIRef("http://localhost#ha"), rdflib.Literal("18")) )
graph.commit()

这就是我所获得的

sbo@dhcp-045:~/tmp/gd $ python ./reader2.py 
table kb_7b066eca61_relations Doesn't exist
table kb_7b066eca61_relations Doesn't exist
sbo@dhcp-045:~/tmp/gd $ python ./reader2.py 
sbo@dhcp-045:~/tmp/gd $ python ./reader2.py 
sbo@dhcp-045:~/tmp/gd $ python ./writer2.py 
sbo@dhcp-045:~/tmp/gd $ python ./reader2.py 
http://localhost/1000 18
sbo@dhcp-045:~/tmp/gd $ python ./writer2.py 
sbo@dhcp-045:~/tmp/gd $ python ./reader2.py 
http://localhost/1000 18
http://localhost/1000 18

对我而言,这似乎是一个错误.修改后的版本告诉我两个三元组属于同一个上下文,并且确实有两个三元组

len : 2
http://localhost/1000 18
http://localhost/1000 18
(rdflib.URIRef('http://localhost/1000'), rdflib.URIRef('http://localhost#ha'), rdflib.Literal(u'18'), <Graph identifier=urn:uuid:a19f9b78-cc43-4866-b9a1-4b009fe91f52 (<class 'rdflib.Graph.Graph'>)>)
(rdflib.URIRef('http://localhost/1000'), rdflib.URIRef('http://localhost#ha'), rdflib.Literal(u'18'), <Graph identifier=urn:uuid:a19f9b78-cc43-4866-b9a1-4b009fe91f52 (<class 'rdflib.Graph.Graph'>)>)

Answer 1

RDF三重存储是一组三元组,因此根据定义,相同的三元组不能出现两次.但是,大多数rdf存储实际上是四元存储(rdf图形集也称为数据集),在这种情况下,三元组可能会出现多次.这有时被称为上下文,取决于商店(例如我的,Redland).权限取决于用户定义特定图形名称/上下文名称的含义.