Extension Update System/Deploying an Update Server
From Joomla! Documentation
< Extension Update SystemRevision as of 06:15, 21 September 2010 by Batch1211
The Joomla Update System handles three forms of updates:
- Extension specific updates (extension.xml file; required regardless)
- Collections of updates that link to extension specific updates (for ease of indexing) (update.xml file)
Extensions and collections can be maintained by hand if required, however it is not advised to use this method for long.