MigrAIRable is a project mainly written in ActionScript, it's free.
An AIR library used to make objects that you serialize migratable
If you are serializing custom classes to disk in your AIR application, what will you do when you want to add an additional field to a class? The readExternal function would not properly read this new field if it was present. What if you wanted to reorder the serialization order of the class? Then the readExternal class would throw a runtime error due to your code trying to read the wrong data type.
The solution: MigrAIRable classes:
It's that easy!
This library won the Adobe AIR Cook-off in 2008. Here's a blog post announcing the initial release.