Major.Minor.Micro – or we can only do so much

When you release a piece of software into the world, then you expect there to be problems. That’s where release number taxonomies come from.
Firstly, let’s define things. There is the Major number. This normally means ‘big things’ have changed. By this, we mean that something so fundamental in the system has changed that there is a good chance that stuff that worked previously won’t work now. It is also referred to as a ‘sea change’ – basically, so much stuff has changed that we can’t guarantee that things will work in the new version because too much stuff has changed. This approximates to the differences between IE7 and IE8 – they tried, but the combination of changes made it impossible to guarantee backwards compatibility.
Then there’s Minor number. This generally means that somethings have changed, but it is compatible with the prior version. You should not need to change things in order to work in the new system. You proably can’t go back, though.
Then there’s the micro version. This means it’s a code change that doesn’t affect the product in any way except to fix issues. This means no config changes, no stored data changes. You *should* be able to swap between micro versions without any issue.