What is the correct way to add relation between swift-proxy and swift-storage by juju

[Ray Wang]

Hello all,

I'm trying to figure out what is the correct way to add relation
between swift-proxy and swift-storage by juju.
I found a link[1] which says

    $ juju add-relation swift-proxy:swift-proxy swift-storage:swift-proxy

But I totally have no idea why add relation between
"swift-proxy:swift-proxy" and "swift-storage:swift-proxy"
I also find there is a README in lp:charms/swift-proxy which says:

    $ juju add-relation swift-proxy swift-storage

I am not sure in which situation, use the former command and which use
later command.

Thanks a lot for the help

[1] https://wiki.canonical.com/InformationInfrastructure/IS/JujuDeploySwift
-- 
Ray Wang
Canonical  www.canonical.com | Ubuntu  www.ubuntu.com