Hello again and welcome to the next tutorial on this series: Part 4 - Sharing data across router methods. Here we are going to learn how to share a object containing data that is available for read across every router methods.
You're required to complete at least the Part 1 before entering this one. Still, this is supposed to be a really short tutorial, since there isn't much to be said about data sharing.
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.

XDATA is used for a whole host of ISC libraries to store things like Zen pages, BPL logic and DTL transformations.