@snakes, I think i am getting confused
By default, I always see www and non-www pointing to public_html folder. I never had to create an alias just for pointing www and non-www point to one location. I guess it depends on type of hosting. Doesn't happen on shared as its pretty much setup already.
By htaccess rewrite I meant, using JUST one version of domain i.e. either www or non-www in order to prevent problems like duplicate content and cookies. For example, I setup non-www as preferred choice in htaccess then a user would be directed to non-www version always, doesn't matter if he enter www in the url.