Obviously, that's only a benefit if you care about and utilize those features; most teams doing JSON integrations will just build those into the consumer in lieu of them being provided by the transport. But it is something that some people (especially larger enterprise organizations) value.
In addition, JSON is easier to parse and to map to common data structures of programming languages.
I'm also not so sure about JSON being easier to map to common data structures. The lack of order guarantees within objects makes things like ordered maps quite annoying (you need to either use an array of entries with key and value, or an index within the mapped objects).
JSON is still figuring it out.
As for DTD: https://en.wikipedia.org/wiki/Document_type_definition
Basically it tells the system what elements are allowed in which places and what attributes they can contain.
<!ELEMENT html (head, body)>
It was kinda-sorta eventually superseded by XML Schema that could also define what KIND of data the attributes could contain, but did exist at the top of XML/HTML/SGML documents for years.
In retrospect, its useful for creating islands of sanity/enforcement in a codebase. Lightweight way to give type annotations across organizational boundaries.
> we use an XML parser to parse it to JSON and even then it's not perfect
I can't quite picture this: how does one parse XML to JSON? I assume there's code that's parsing XML and returning a JSON object? What would make this not perfect, other than a poor implementation of the translator? Would them using JSON help? If JSON is a less expressive format than JSON, is it possible to 100% translate their XML to JSON?
Thanks for the insight! Is this what JSDoc/Swagger is now used for?
> I can't quite picture this: how does one parse XML to JSON?
I'm not sure actually. I haven't personally seen the code, I just hear my coworkers always lambasting that API provider for their usage of XML. Maybe it's just their lack of documentation that sucks, but it's become a running joke whenever we get a new partner that the team integrating it jokes that their API is XML.
I hear this too, but often when I ask why people say things like that, it's either because XML is "outdated" or because they don't like it.
It's like programs written in C or C++: very few large projects chose those languages nowadays, often for good reasons, so the projects written in those languages are usually 10 to 20 years old. Age comes with a lot of legacy cruft and obscure behaviour, but that's not the fault of those languages per se. Or for people blasting banks for using COBOL, even though COBOL is a perfectly fine high-performance language for the niches bank mainframes serve.