Upgrading Mediawiki from version 1.5.6 to 1.15.0

Hello,

I'm running MediaWiki version 1.5.6 and would like to upgrade to current
version (1.15.0).
What is the procedure to upgrade ? Is the database compatible ? What about
configuration files ?

Thanks for any advice.
--
francois.piette <at> overbyte.be
Author of ICS (Internet Component Suite, freeware)
Author of MidWare (Multi-tier framework, freeware)
http://www.overbyte.be