if ( ! tokenizer.hasNext() )
throw new TDBException("Failed to tokenise: "+str) ;
Token t = tokenizer.next() ;
try {
Node n = t.asNode() ;
if ( n == null ) throw new TDBException("Not a node: "+str) ;
return n ;
} catch (RiotException ex)
{
throw new TDBException("Bad string for node: "+str) ;