It might be helpful to think about the context bar as one
instantiation of a variety of site-wide navigation aids a developer
might want to build. For example, you should be able to use the
same information (about the navigation tree that's required for
the context bar) to generate a hierarchical pull-down or left-side
menu.
If what we end up with is some kind of a navigation
service-contract, then it might make sense to look at the degree
to which it could integrate with site-map. (I don't really fully get
site-map yet, but that may just be me being dense.) There
should be one central place that makes it easy and intuitive to
organize the site-wide (or sub-site-wide) navigation tree.
