[Boost-users] [BGL] Trying to use subgraph

I've been trying to work out how to use the subgraph adapter. I've come to realize that in order to use it, my primary graph must *itself* be an object of the subgraph type (unintuitive). However, I'm getting a static assertion error that edge_index is an unknown property. I had *thought* that an adjacency_list would not have that issue, but apparently I was wrong. The page here: http://www.boost.org/doc/libs/1_39_0/libs/graph/doc/subgraph.html says "we add an edge index property to the adjacency list", but the code which follows demonstrates no such thing. The distinction between bundled properties and internal properties is still a bit mysterious to me. Can anyone shed some light on this?