What about an attributes without namespace like:
style="?android:attr/starStyle" ?
Good question. Now I use "android:" namespace by default (if no other namespace was given). So, for custom namespaces you write "mynamespace:foo", for android namespace - just "foo".
I've just updated AAML to use prefix "=:foo" for default namespace or no namespace. If you prefer other syntax for empty namespace - you are welcome to suggest!