:- use_module(library(semweb/rdf11)). [semidet]rdf_is_bnode(@Term)
[semidet]rdf_is_bnode(@Term)
A blank node is represented by an atom that starts with
_:.
Success of this goal does not imply that the blank node is present in the database (see rdf_bnode/1 for that).
For backwards compatibility, atoms that are represented with an atom 
that starts with __ are also considered to be a blank node.
:- use_module(library(semweb/rdf_db)). rdf_is_bnode(+Id)
rdf_is_bnode(+Id)_:. 
For backward compatibility reason, __ is also considered to 
be a blank node.