(I can't downvote direct replies, so it wasn't me.) I was not suggesting that you incorporate it. I was suggesting modifying your marketing copy to incorporate the fact that it will not be a superset anymore. Superset is a word we should guard and not let it become "sort of superset-ish, maybe, mostly", but should mean superset. If you don't have every feature, you should not say it's a superset. Since not only is there nothing wrong with feature elimination, but when done well is a downright good thing, it's not like this is some sort of major problem for the marketing or something; just say you used some taste in what you brought over.
And again let me emphasize, since you seem to be saying it again in some other replies, that "{mark} is a superset of JSON", if you mean that syntactically (as opposed to features wise), MUST mean that every valid JSON document will produce a valid {mark} parse. Nothing less than that qualifies it as a superset. Given that you reserve numeric keys I don't think that is the case; whether the grammar is a superset is harder to determine so I haven't tried. That would be something best served by taking a very complete JSON parser test suite from someone and validating that all their corner cases that are supposed to parse in JSON, parse in {mark}. Based on my own experience in the world of parsing, the odds of you passing that first try are very low; if you manage, major kudos to you as that would be a very difficult test. (Though I would imagine that since the grammar largely came from JSON a lot of the surprises would be the ways in which your parser turns out to deviate from the grammar rather than grammar errors.)
And again let me emphasize, since you seem to be saying it again in some other replies, that "{mark} is a superset of JSON", if you mean that syntactically (as opposed to features wise), MUST mean that every valid JSON document will produce a valid {mark} parse. Nothing less than that qualifies it as a superset. Given that you reserve numeric keys I don't think that is the case; whether the grammar is a superset is harder to determine so I haven't tried. That would be something best served by taking a very complete JSON parser test suite from someone and validating that all their corner cases that are supposed to parse in JSON, parse in {mark}. Based on my own experience in the world of parsing, the odds of you passing that first try are very low; if you manage, major kudos to you as that would be a very difficult test. (Though I would imagine that since the grammar largely came from JSON a lot of the surprises would be the ways in which your parser turns out to deviate from the grammar rather than grammar errors.)