Hello!
My goal is to serve files using REST classes only (no filesystem should be used), and I am a halfway far from it.
What I am succeeded in, is serving character files (html/css/javascript/etc) using the next approach:
InterSystems ObjectScript is a scripting language to operate with data using any data model of InterSystems Data Platform (Objects, Relational, Key-Value, Document, Globals) and to develop business logic for serverside applications on InterSystems Data Platform.