Hi Yes when changing edges or vertices in the original or filtered graph it will affect both graphs as mentioned in other response the filtered graph is just a mask. Therefore it is really easy to change the filtered graph fg (using an attribute to filter on).
I know I could write a simple test to find out, which I am doing, but I'd be grateful if someone with more experience of BGL could let me know of any exceptions or potential pitfalls.
As mentioned a lot in the BGL online litterature a "pitfall" is that the num_vertices(fg) reports the num_vertices(g) and does not refelct the number of vertices in fg. Also remember that changes such as deleting edges in the filtered graph will result in deleting edges in the original as well. Hope it makes sence. Best Line Reinhardt