[boost] bgl question: in which namespace to put the functions

Hello, Developping code so that BGL algorithms can run on the vertices and edges of CGAL triangulations, I am wondering if there are rules or recommendations for in which namespace the functions source, target, vertices, out_edges ... shall go. In boost, because it is boostish code, or in CGAL, because that is the namespace where the triangulation lives in? thank's in advance, andreas