If I recall correctly, the Cisco commands "write memory" and "copy running-config..." always indent child nodes by one space. I never wrote anything that depended on the indentation, but it certainly looked consistent enough to use in parsing the files. YMMV.
in reply to Config files To XML
For example, this is a fragment of a lab router config for a 7200:
So "no ip address" and "duplex full" are child nodes of "interface FastEthernet1/0" because they are indented farther to the right.
no ip address
encapsulation dot1Q 1 native
ipv6 address xxxx:1::3/48
ipv6 traffic-filter lab-only in
ipv6 ospf 1 area 0
line con 0
line aux 0
There are a few cases where second-level child nodes exist and are indented by two spaces, but I don't have any examples handy. Oh, and by the way, don't try to use the exclamation points in parsing; they are not nearly as consistent as the spacing.