I agree with that, but in this case, the author had already scoped it down to services calling other services in a "microservices" context. And even if the cal

I agree with that, but in this case, the author had already scoped it down to services calling other services in a "microservices" context. And even if the call graph is a->b->c->a->b, I can still say up/down if I give the context of which invocation. I'm hoping people don't do that much in real life though, too easy to recurse.