AFAIK, you can't using Apache
, As all Apache can serve is URL's, they have to be in the scope of the server (the DocumentRoot) OR on some other resolvable resource.
Yous should also look at your post title, and realize/understand what a URL is. http://en.wikipedia.org/wiki/Uniform_Resource_Locator
What your post title inplies is absolute vs. relative URL's
not filesystem locations,
Take a minute and try thinking this through - would you want people to be able to scan your machine if you made a minor error in your configuration settings?