As far as I know, from iOS SDK 3.2, file type handling is added and an iOS application can associate itself with some file type so that other applications can open this kind of file with the application.

Because of the sandbox mechanism in iOS, I wonder when a file in appA is opened with appB, which registered itself with this kind of file, what will happen? Is this file copied to appB and both appA and appB keep a copy of this file? If the answer is yes, is it possible to make appB open the file under appA's document folder? I cannot find any Apple documentation on this.

For example, appA stores a Keynote document in it, if I open this Keynote document with the Keynote app, is it possible to let Keynote app to edit this document in place so that after editing, appA can see the updated document?

Any help is appreciated.