Best practices

I've been thinking about best practices / versioning more than anything, lots of ambiguity and flexibility today

one question people have is "how can I design & test lexicon before I know exactly what is needed?" How can I update / expand them once the are being used? How can I upgrade old records to the latest schema?

I'm def thinking about versioning and dependencies

Another question, if I use the community event lexicon

How should adding extra fields I need for my app work?

What happens if the common lexicon gets an update and my app is still producing older records?

How does an app transition to/from a common/custom lexicon?