Magento: what does option "before" do in config.xml file? - magento

Question

I added admin controller.
This code works correct:
<admin>
<routers>
<adminhtml>
<args>
<modules>
<mycompany_mymodule>Mycompany_Mymodule_Adminhtml</mycompany_mymodule >
</modules>
</args>
</adminhtml>
</routers>
</admin>
If I add before="Mage_Adminhtml" to mycompany_mymodule:
<mycompany_mymodule before="Mage_Adminhtml">Mycompany_Mymodule_Adminhtml</mycompany_mymodule >
then it doesn't work - got 404 error.
1. What does this option do?
Also I looked throught Alans' Storm article: http://alanstorm.com/magento_admin_controllers
There are example:
<config>
<!-- ... -->
<admin>
<routers>
<the_name_of_this_element_is_not_important_it_should_be_unique>
<use>admin</use>
<args>
<module>Alanstormdotcom_Adminhelloworld</module>
<frontName>adminhelloworld</frontName>
</args>
</the_name_of_this_element_is_not_important_it_should_be_unique>
</routers>
</admin>
<!-- ... -->
</config>
2. What is the difference between these definitions?

Answer 1

It solved:
I found Mage_Core_Controller_Varien_Router_Standard class where collectRoutes() method is defined. It parses "after" and "before" parameters to order the modules.
This method is calling from Mage_Core_Controller_Varien_Router_Admin (started from init method in Mage_Core_Controller_Varien_Front).
So after I looked through match process in Mage_Core_Controller_Varien_Router_Standard.
After Mage_Core_Controller_Varien_Router_Standard debuging I understood my fault.
I used Index controller instead of MyModuleContoller.
Alan Storm defined controller which is not under the admin module (i.e. adminhtml). When I use first config - it works perfect because I defined new modules under the section adminhtml. In Alan's config I cannot add my module to adminhtml. I could override it but it is not correct because other modules under the adminhtml will be removed then.
This is correct code for menu under the adminhtml:
<admin>
<routers>
<adminhtml>
<args>
<modules>
<mycompany_mymodule after="Mage_Adminhtml">Mycompany_Mymodule_Adminhtml</mycompany_mymodule >
</modules>
</args>
</adminhtml>
</routers>
</admin>
Inchoo also described this config here.