Parents & Children
A service can be a parent for other services.
It's just a way of organizing your services and grouping them.
You will typically do it for indicating some kind of child/parent relationship, e.g. an app living inside a node.
The parent/child relationship defines the location in the AYS repo directory structure (so purely visualization).
Child services also inherit their parent's executor defined in getExecutor
by default.
See the section Parent/Child for more information on this topic.