0.6.4 namespace introduction?

[eriknelson]

0.6.4 added a change to the answer file format that namespaces(?) a graph nodes name by what appears to be the container name? For example:

Valid 0.6.4

[mariadb-centos7-atomicapp:mariadb-atomicapp]
db_pass = changeme
image = centos/mariadb
db_user = erik
root_pass = MySQLPass
db_name = test

NOT Valid 0.6.4

[mariadb-atomicapp]
db_pass = changeme
image = centos/mariadb
db_user = erik
root_pass = MySQLPass
db_name = test

Curious what the background is behind this change and why its necessary. It's not clear to me what each identifier actually is? They appear to be very similar, all I can glean is that one looks like a container name, and the other is potentially a nulecule name?