Updating drupal 6
The numbers are composed of three parts: A good rule of thumb is to remove updates older than two major releases of Drupal.
See hook_update_last_removed() to notify Drupal about the removals.
The documentation block preceding this function is stripped of newlines and used as the description for the update on the pending updates task list. Implementations of hook_update_N() are named (module name)_update_(number).
An update function can force the current and all later updates for this module to abort by returning a $ret array with an element like: $ret['#abort'] = array('success' = ' What went wrong'); The schema version will not be updated in this case, and all the aborted updates will continue to appear on as updates that have not yet been run.
Multipass update functions will also want to pass back the $ret['#finished'] variable to inform the batch API of progress.
Core modules also includes a hierarchical taxonomy system, which lets developers categorize content or tagged with key words for easier access.
Drupal localization is built on top of gettext, the GNU internationalization and localization (i18n) library.