rewrite rules with apache does not work - mod-rewrite

Question

I try to make specific rewrite rules by .htaccess but i need help, its doesn't work.
This is my url :
http://mywebsite.net/aaa-bbbb/cccc
aaa = dynamic parameter ( [a-z] )
bbb = dynamic parameter ( [a-z] )
cccc = dynamic parameter but optionnal ( [a-z] )
And i want rewrite user to this url :
http://mywebsite.net/mydir/ccc?x=aaa&y=bbbb**
url still will http://mywebsite.net/aaa-bbbb/cccc on tabbar
i try this
RewriteRule ^([a-z]+)-([a-z]+)/([a-z]+)$ mydir/$3 [L]
but it doesn't work
thx !

Answer 1

To rewrite a request to
http://mywebsite.net/aaa-bbbb/cccc
internally to
/mydir/ccc?x=aaa&y=bbbb
you need such a rewrite rule:
RewriteEngine on
RewriteRule ^([a-z]+)-([a-z]+)/([a-z]+)$ /mydir/$3?x=$1&y=$2 [L]
Note: the above rule has the syntax to be used inside the http servers host configuration. If you really want to use a .htaccess style file instead you need to use a slightly modified syntax, since those files work on relative paths:
RewriteEngine on
RewriteRule ^([a-z]+)-([a-z]+)/([a-z]+)$ mydir/$3?x=$1&y=$2 [L]
You can spot the missing / in the rewrite goal. The .htaccess style file has to reside inside the folder holding the mydir folder for this to work. Also the interpretation of such files has to be enabled at all in the http server configuration for.
A general note: .htaccess style files are notoriously error prone, hard to debug and they really slow down the http server for nothing. They are only offered as a last option for those not having access to the http servers host configuration. So for example for cheat shared hosting providers. In general you should always prefer to place such rules inside the host configuration itself.