The idea of supplying a spec to transform arbitrary data is interesting to me. I did one in JavaScript called Reshaper[1], and then hooked it up to a library wrapper called Smolder[2].

The result was a sort of system whereby data going into a function would be automatically 'reshaped'. It worked well as a proof-of-concept, but obviously was too fragile for most uses (though it's used in the automatic graphs in Kajero[3]). The difference here seems to be that the spec defines the actual transformations, rather than just the desired final structure.

[1] https://github.com/joelotter/reshaper [2] https://github.com/joelotter/smolder [3] https://github.com/joelotter/kajero