When configuring Experience manager, you have to configure the Ambient Data Framework both for the staging site, and for the Preview Webservice. Some of the reasons for this are obvious enough, but I'm left with the idea that I don't have the full picture of what's going on.
So to start with, I'm assuming that these days ADF is pretty much the standard way for content delivery components to get access to a cookie. The staging site needs to see the XPM session token cookie so that it can grab preview content from the preview database, and it makes sense for the ADF to be used for this.
It seems also that use is made of ADF's session management, and that the end of a session triggers the cleanup of temporary files that are created by the filter/module in the web application.
It is less obvious to me why ADF needs to be present/configured for the Preview Webservice. Is there also a session cookie here? (I had assumed the session token was part of the payload.) What is the ADF used for here?
Have I understood it correctly so far? Are there other parts of the Experience Manager dance which are choreographed by the ADF?