drupal code implements URL rewrite

Here is an example of the implementation:

 
/* 
*  Pseudo address to original address  (url_alter) 
*/ 
function example_url_inbound_alter(&$path, $original_path, $path_language) 
{ 
if (preg_match('|^article(/.*)|', $path, $matches)) { 
$path = 'node'. $matches[1]; 
} 
} 
/* 
*  Turn the original address into a pseudo-address  (url_alter) 
*/ 
function example_url_outbound_alter(&$path, &$options, $original_path) 
{ 
if (preg_match('|^node(/.*)|', $path, $matches)) { 
$path = 'article' . $matches[1]; 
} 
} 

PS: when implementing hook_url_inbound_alter, I don't know why I can't call the implementation function. Maybe because HOOK loaded too early, module was not fully loaded. So what I did was write it in the URL rewrite module, such as subpath_alias