How to evolve complex state (e.g., annotate data)?

Hi Adrien,
thanks for the responses. I already checked out the SessionState code and implemented a proof-of-concept of an annotation script, but it still feels very hacky and is far from readable.
Can you elaborate on the ignore_hash idea? I don’t see how hashing (or not hashing) the output of a function call changes anything.
Maybe my other question (Memoize/cache partial function) goes into a similar direction? If you allow a function to be executed another time, if the last call with the same arguments yielded None, I could see how to implement an annotation script.