Is there any guide to xml?

Sorry if I have failed to notice the obviouse
Is there any definition of the xml used in watch faces. At the moment I’m finding what I can find out from the xml of others faces. I know there must be much I dont have examples for. So a guide that eg. lists all array types and their options would be very appreciated.

You might have a look at this post:
-Array Types for Watchfaces (Calories, Distance, etc.) - #17 by Odin


ohhhh, so this is indeed a dark and mysterious corner of scripting with just a hint of hacking.
Thank you muchly
I shall now meditate on the theme of Satanic code confustication!