is there a way or pattern to indicate that two values are related or constrained? I have a map and there’s validation for that, but I would also like to say “start” (a date) is before “stop” (a date). I can’t quite piece together what to do.

one other question, for RESTful APIs, it’s often the case that all the keys are required for a POST but only some are required for a PUT, does anyone have a design pattern for that?