How do I add a new item to a schema file?

[Evalis]

Breaking this up into two parts:

Part 1:
Let's say I want to add an option into a schema that already exists in other schema's, such as adding bonus trade routes to a trait, or adding health to improvements.

Can this be done purely via xml? What would be the line of code required to do so (assuming this can be easily edited).

Part 2:
Let's say I want to add an option into a schema that does not exist, such as a penalty to research when at war. Is such a thing possible, and would it require editing the dll or python, or both?

 

[The_J]

1) No, not possible via XML.
To make a tag work, you'd have to code it's functionality into the .dll.

If you want to try your hands on C++, there's a tutorial for "copying" a tag from one file to another here, and there's a tutorial for compiling the .dll here.
But attention, this is nothing which is done in 5 minutes (...probably not even days if you don't know what this is all about).