XFL - What's the best way how to generate DOMBitmapItem's itemID?

XFL's DOMBitmapItem tag has attribute itemID. What is safe way how to generate such an ID if I want to add new media items from external tool?

The example of itemIDs looks like:

itemID="4cd开发者_运维问答28f37-00000036"
itemID="4cd1d136-0000029a"
itemID="4cd1bd22-0000003b"

So far it looks the best way is to not use this attribute when inserting new bitmap item at all and let the Flash IDE to add it during it's load time.

Anyway, the first part (like "4cd2a469") is hexadecimal representation of Unix epoch.