Also Prismatic's schema. It achieves some of the same goals for why you would want strong typing:

https://github.com/Prismatic/schema

+1 for Prismatic Schema. It's not only an awesome way to validate your maps, but it is an extremely good way to write documentation.

It's also very worth looking at Typed Racket and Racket's contracts system!

    [1] http://docs.racket-lang.org/ts-guide/
    [2] http://docs.racket-lang.org/guide/contracts.html?q=contracts

Thank you for the link. I will look into the core.typed.