Var v = Var.alloc(gn) ;
Op union = null ;
for ( Node n : namedGraphs )
{
Binding b = BindingFactory.binding(v, n) ;
Op x2 = QC.substitute(opQuadPattern, b) ;
Op op = OpAssign.assign(x2, v, NodeValue.makeNode(n)) ;
union = OpUnion.create(union, op) ;
}
return union ;