I am looking for a schema language that allows definition of functions. I thought of http://json-schema.org/ at first, but that format is data-only. My knowledge from XSD is the same.
The language is at first not important, my project is just starting, so there is plenty of flexibility. The thing which, i think, is important, is to be able to model a datastructure containing functions.
Ultimately it is possible to model a function with the data-only literals, which will be my last resort if no good language with native support exists.