[Boost-users] [graph] named vertices?

I notice that in the changes for the newest boost that "named vertexes" is now supported in adjacency_list. I can't find anything on this feature though. I have the book, have searched the web. Only thing I find is comments in adjacency_list.hpp that maybe refers to a NamedGraph concept? I don't see that in the docs either: http://www.boost.org/doc/libs/1_39_0/libs/graph/doc/table_of_contents.html Could someone give me an overview of what this feature is and why I might use it? Probably better...point me to some place that documents it?