Why does it have to have a chat interface? What's wrong with entering airports in different fields? I'm not convinced it's needed for a "routine trip" feature, you could just have some sort of bookmark feature..
We've included chat as an option for those who prefer it. I personally find it easier than clicking a bookmark and manually adjusting the dates each time. However, we understand that many people prefer entering fields themselves, so our UI supports that as well.
We see chat evolving into a concierge that can handle the same tasks you’d give a human assistant: planning entire flight + hotel itineraries, rescheduling flights, checking in to upcoming trips, etc.
I haven't gotten around to it yet, but my plan is to use in-process REST with Objective-S, so that accessing the internal endpoint will be the cost of a function call.
The integer numbers can be divided into "negative" (less than zero), zero, and "positive" (greater than zero). When one says "non-negative", they are excluding only the negative numbers, so zero is included; when one says "positive", zero is not included.
It really is, in-universe. Almost noone knows this save other maiar. The wizards are perceived as men by most people, them being maiar is far from common knowledge.