Look closely at URI's for ordinary web resources. Those are your template. Think of directory trees; use simple Linux-like file and directory names.
HelloWorld
isn't a really good class of resources. It doesn't appear to be a "thing". It might be, but it isn't very noun-like. A greeting
is a thing.
user-id
might be a noun that you're fetching. It's doubtful, however, that the result of your request is only a user_id. It's much more likely that the result of the request is a User. Therefore, user
is the noun you're fetching
www.example.com/greeting/user/x/
Makes sense to me. Focus on making your REST request a kind of noun phrase -- a path through a hierarchy (or taxonomy, or directory). Use the simplest nouns possible, avoiding noun phrases if possible.
Generally, compound noun phrases usually mean another step in your hierarchy. So you don't have /hello-world/user/
and /hello-universe/user/
. You have /hello/world/user/
and hello/universe/user/
. Or possibly /world/hello/user/
and /universe/hello/user/
.
The point is to provide a navigation path among resources.