ubuntu - Linux directory permission inheritance -

can explain me how directory permissions inherited in linux (ubuntu, specifically)?

for example, if have following directory structure:

folder_a     folder_b 

do folder_a's permissions override folder_b's? there difference if folder_a's permissions more restrictive folder_b's, or vice-versa?

my guess if folder_b had more restrictive permissions, override folder_a's, if folder_a had more restrictive permissions, override children.

the way permissions affect paths explained in path_resolution man page: http://linux.die.net/man/2/path_resolution

the permission on folder matters search (execute) permission: if don't have can't descend folder b. other there no relation between permissions of , b, example if read-only , b not, or if don't have read permission a, still can create , delete files in b.