>> S-Expressions >>Okay? Is that useful

Yes, super useful. Depends on how your application needs to use S-expressions. You could define DSLs for a very expressive and complex rules-engine with S-Expressions forming your rules. Now you can write your rules as text, pass it around and build rule evaluators of those expressions all on top of Ion.

> Okay? Is that useful?

I bet it's super useful if you have sexprs in your data.

It's interesting to have languages written for and in the same specification as your data.