RDF newbie - describing folders

Dear all,
I apologize for the silly questions.
My problems are:

- is it possible to describe, using RDF, a whole folder of files 
(i.e., images) as a single entity? In other words, may I use 
something like:
<description about="http://www.blabla.net/folder/"> to identify the 
description of a folder, or is it interpreted as web servers use to 
do?

- furthermore, is it possible to refer to relative URI, in order to 
add metadata to not necessarily online resources? (e.g., to describe 
resources on a removable medium).

Of course, I have some other unclear things in my mind... but let's start.

Thank you very much.

Vincenzo Della Mea