iOS 5: iPod Library Access, pt 2

Hello all, Is an _artist_ an MPMediaItemCollection of albums, or an MPMediaItem / Entity? If the later, how do I get it's MPMediaItemPropertyPersistentID? Is an _album_ an MPMediaItemCollection of songs, or an MPMediaItem / Entity? If the later, how do I get it's MPMediaItemPropertyPersistentI

iOS 5: iPod Library Access

Hello, all ... I'm trying to navigate the artists / albums / genres / etc. on a device. The documentation for this is usually easy to follow, but i'm finding it to be confusing regarding the concept of persistent IDs. I've a couple of questions: 1. What does and what does not have an MPMediaIt