Hi,all Can I define an edge in ALPS but do not define the any bond operator depending on it? For example, I define the type 0 ,1,2 edges, but only type 0,1 bond operator. I know someone will say since you do not use the type 2 edge, then why you define it. OK, as my argument, I just want to know whether it works. So, what is the answer? Bo-Nan -- Stay foolish,Stay hungry.