Yup - as a result, there's usually a TON of interesting SQLite files on any Mac (and iPhone too if you can get at them).

Sometimes you can pull the phone ones out of backups. You used to be able to mount an application's full directory tree, but Apple killed that API years ago.

I believe you can choose the kind of store you want for Core Data. (SQL is probably the most popular though.)

You can choose between:

1. XML-based (the entire database is one xml file)

2. SQLite-based

3. Roll your own (by providing an implemention)

#1 is terribly slow for most cases and not publicly available on iOS.

#3 was released early in the ioS lifecycle (iOS 3 or iOS 5, depending which piece we're talking about)

SQL is, for most purposes, the only implementation, except for iTunes which used #1 for a decade after #2 clearly won.

iTunes uses a proprietary database format IIRC, but keeps a copy of it in XML on the side so other people can read it if they want.