rule Trees 
	merge l : Core!Tree
	with r : Fragment!Tree
	into t : Target!Tree {
	
	t.label = l.label;
	t.children ::= l.children + r.children;
	
}

rule Tree2Tree 
	transform s : Tree!Tree
	to t : Target!Tree {
	
	guard : s.label <> "f_root"
	
	t.label = s.label;
	t.children ::= s.children;
	
}