Alias in htaccess with rewrite module

I am trying to install mysource matrix on a shared host, I appreciate that this is a near impossibility


I have managed to get to the stage of setting up aliases in the httpd.conf

of course being a shared host I dont have access to the httpd.conf



i have seen it referenced in several places that it is relatively easy to set the aliases up as rewrites in the .htaccess

however after searching the forums and the web i haven't been able to find any where that explains the rules you need to setup

and all my experimentations have failed



does any one have any knowledge of this or know somewhere that it has been discussed?

Here is a sample .htaccess file:

    Options +FollowSymLinks
    RewriteEngine On
    
    #Set the base uri (i.e. the URL to matrix)
    RewriteBase /
    
    #Now do some rules for redirection
    #if index, don't redirect (again)
    RewriteRule index.php   - [L]
    
    #don't redirect double-underscore dirs
    RewriteRule __lib	   - [L]
    RewriteRule __data	  - [L]
    RewriteRule __fudge	 - [L]
    
    #redirect everything else to index.php
    RewriteRule (.*)		index.php/$1 [L]