Forum OpenACS Development: Response to Breadcrumb trail service?
Working just off the site map doesn't work for the other style, either, as you want nav bars like:
... | New Post | Confirm New Post
where the "new post" and "confirm" pages are in the same directory within the site map. So the site map can build the first part of a nav bar that locates you within the URL "directory" structure, but not
the last part that lets you move around files within that "directory".
And it helps even lest if you adopt the "nav bar should reflect the path the user took to get here" paradigm.