crossdomain.xml file for AIR app

Hi
I am just adding a crossdomain for an AIR project.
I understand crossdomain in general, where I tell domainA.com to allow calls from DomainB.com.
But if DomainB is my AIR app, then what's the "domain" value??
I would prefer NOT to allow all, but I'm not sure how to restrict it for AIR apps coming from different locations.

Thanks!