Resources for Learning to Model OPC UA Interfaces?|OPC UA Implementation: Stacks, Tools, and Samples|Forum|OPC Foundation

I am struggling to understand the modeling aspect of OPC UA.  I understand there are tools to create models (XML) and this tool to compile them into nodesets (XML) https://github.com/OPCFoundati.....elCompiler .  However, I have found the tools lacking in certain abilities or they just fail to operate.

I have tested the following modeling tools:

opcua-modeler - Python tool, but it fails to load https://github.com/OPCFoundati.....iModel.xml

https://github.com/beeond/opcu.....eling-tool - Fails to load the same xml files and has basic errors on file encodiing types

UaModeler v1.6.2 - Can not find any way to load an xml file.  Attempts to import xml files into project fail.  Not useful if I cannot load existing models.

The biggest thing I am struggling with is finding something that explains what actually goes into a model file.  For example:

https://github.com/OPCFoundati.....oModel.xml

This is a demo model that shows a simple model.  However, there is an attribute used on references called "IsInverse".  I have no idea what that means.  I searched the OPC UA specs and cannot find it defined as to what it actually does.  If it is in the specs it is like a needle in a 1300 page haystack.  What I think I really need is a reference for OPC UA modeling, but scouring the internet turns up zero.  I have been staring at OPC UA intro videos that only show block diagrams which are almost useless when trying to program something.  What I would really like is a book that describes in detail the OPC UA modeling process using XML files.  I am not certain any of the books on Amazon describe anything more than this is what OPC UA is from a conceptual point of view. 

Another frustrating aspect is the OPC UA specs describe the rules for using the different pieces in modeling, but never actually show a single line of XML.  Is this because the XML portion is just one possible expression?

So, TL;DR.  I am looking for a digestible explanation of how to program the XML portion to feed to the UA-ModelCompiler.  From there I will use the resulting nodeset to feed to a code generator for my server/client interfaces.  Please let me know if there are active groups that talk via forum or chat.  That would be extremely useful.

Thanks for any help or resources you can point me to.