For example P(a, b): - A(a, c), B(b, c). How can I ensure 'a' and 'b' are different? Does this policy already imply that they are different? Or I need to explicitly indicate that they are different? If so, then how can I do that? Thanks, -- Su Zhang Senior Software Engineer Symantec Corporation -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openstack.org/pipermail/openstack/attachments/20151014/f3f96634/attachment.html>