I think we mostly agree, but would put it a bit differently. First, I think performance is a bit of a red-herring in this discussion. If a linear scan is reall

I think we mostly agree, but would put it a bit differently. First, I think performance is a bit of a red-herring in this discussion. If a linear scan is really faster for five entries, a good dictionary implementation could simply switch to that. Second, and more to the point, there’s a obviously a semantic difference between a list of pairs and a dictionary. That’s always going to be part of the “protocol” - whether your serialization format is capable of expressing that or not. However, and I think this is where we agree, there are lots of semantic distinctions that JSON can’t express (dates vs. strings, to pick an example I encounter often). So in many cases, you’re going to have a deserialization step anyway that validates the JSON values and converts them into the objects you actually want to use in your application. Why, among all the semantic distinctions that JSON doesn’t capture, is the list/dictionary distinction so special that it needs this kind of syntactic support in a serialization format? (BTW, for JSON, the answer is obviously rooted in JavaScript’s type system. But while that makes it particularly nice to use JSON to serialize JavaScript objects, the context here is its use as a general-purpose serialization format.)