rule Tree2Node 
	transform t : Tree!Tree
	to n : Graph!Node {
	
	n.name = t.label;
	
	// If t is not the top tree
	// create an edge connecting n
	// with the Node created from t's parent
	if (t.parent.isDefined()) {
		var e : new Graph!Edge;
		e.source ::= t.parent;
		e.target = n;
	}	
}