Question about Jena RDQL and blank nodes.

Hi,
I apologize if this message reached the list twice, there may be some 
problem with the network here.

I'm trying to build a tool to interactively visualize RDF graphs.
The idea is to allow the user to start from a resource/literal (or from 
a graph pattern) and dynamically explore the content of an ontology/RDF 
graph, basically choosing how to expand the graphs and 
selecting/distinguishing namespaces (and with the ability of displaying 
large graphs).
I'm using the Protégé OWL API to parse the ontology (really this 
project is part of something else that may address the owl level), 
generate an OntModel and use RDQL Jena support to make queries.

When I make a query and get(Var) out of ReslutBinding, I only have a 
method to string (even if I cast it to RDFNode). This gives a URI for 
resources or properties, but just a representation of the pointer for 
blank nodes.
Is there any way to have a unique identifier for blank nodes to use in 
other queries ? (in Protégé OWL API there is).
Is there any method to know if a variable has a blank node as value ? 
(I may test if it is a well formed URI...)

Another question:
is there a way to ask for an approximate matching of literals ?

best,
Andrea Splendiani