> It is a property of the data itself, not a property that a person chooses for the file like, say, the file name. I entirely disagree. If I have an empty .jso

> It is a property of the data itself, not a property that a person chooses for the file like, say, the file name. I entirely disagree. If I have an empty .json or empty .bin or empty .txt I expect a different behaviour in the software that I am opening the file with, even if in all cases the actual data is zero bytes. More generally file formats can be polyglots: https://github.com/Polydet/polyglot-database https://github.com/Polydet/polyglot-database