为什么空白节点不作为链接显示在资源页面上，而不显示在可视化图表上？

Question

Ontotext GraphDB 9.1.1, Free Edition Centos7 3.10.0-1062.9.1.el7.x86_64

One of my graph that contains blank nodes like this:

@prefix : <urn:ex:> .
:John :weight [ :value "5" ;
                :unit  "kg"  ] .

When I searching John in the Explore/Graphs Overview for the default graph, triples are displayed and the subject :John has a object called _:node3.

However, the object is displayed as text rather than a resource link like a :John.

And I click Visual Graph for :John, nothing is displayed.I tried Advanced Graph Configuration , also failed.

I found some solution that using CONCAT to merge object, but it's not enough graceful.

What I expect is that blank nodes could be displayed on Overview and Visual Graph .

Is that possible no matter what version of graphDB?

Thanks!

Answer 1

A blank node is a node that does not have a IRI as its identifier. That's the reason the Visual Graph shows only IRIs. Ideally you should avoid using blank nodes as it will be inconsistent with the fact that :John is IRI and you are using blank node to define it's properties.Here's a workaround (I'm not sure if you found this one):

prefix : <urn:ex:>
CONSTRUCT { 
    :John :weight ?value
} WHERE {
    :John :weight ?bnode.
    ?bnode :value ?nameLiteral;
       :unit "kg" .
    BIND( IRI(CONCAT("http://test", ?nameLiteral)) as ?value)
}