Core Data with Multiple Entities?

[Whitehk]

I finally got through Apple's Core Data tutorial that has you create an application called "Locations". I think I've got a pretty good handle on the basics of the framework at this point; however, I can't seem to figure out how to implement core data with multiple entities.

I took a look at Apple's PhotoLocation, CoreDataBooks, and TagLocation sample code, but those were essentially useless to me due to the fact that it gave little explanation as to what it all really meant.

Does anyone have some good tutorials that really show what Apple was trying to exemplify in the PhotoLocation, CoreDataBooks, and TagLocation projects? Maybe a detailed explanation of these projects? Any references (including books) to this type of advanced core data implementation are welcome.