Well think of it this way, your directory looks something like
DC=root,DC=com
CN=Builtin,DC=root,DC=com
CN=Computers,DC=root,DC=com
OU=Domain Controllers,DC=root,DC=com
CN=ForeignSecurityPrincipals,DC=root,DC=com
CN=Infrastructure,DC=root,DC=com
CN=LostAndFound,DC=root,DC=com
CN=NTDS Quotas,DC=root,DC=com
CN=Program Data,DC=root,DC=com
CN=System,DC=root,DC=com
CN=Users,DC=root,DC=com
DC=child,DC=Root,DC=com
CN=Builtin,DC=child,DC=root,DC=com
CN=Computers,DC=child,DC=root,DC=com
OU=Domain Controllers,DC=child,DC=root,DC=com
CN=ForeignSecurityPrincipals,DC=child,DC=root,DC=com
CN=Infrastructure,DC=child,DC=root,DC=com
CN=LostAndFound,DC=child,DC=root,DC=com
CN=NTDS Quotas,DC=child,DC=root,DC=com
CN=Program Data,DC=child,DC=root,DC=com
CN=System,DC=child,DC=root,DC=com
CN=Users,DC=child,DC=root,DC=com
If you do a search from root, it is logical that it flows through the children
as well as they are beneath the main root structure i.e. subordinate.
If you switch to a GC search you should get away from the referrals though since
the GC maintains a subset of all attributes.
joe