I recently was dragged into a JSON vs. XML debate. There are definitely some people out there with strong opinions on this matter. I'm not really one of them. However, most web developers I've worked with like how easy JSON is to work with. That's good enough for me. Plus, some of the typical pro-XML arguments are particularly disturbing to me:
- XML has strong typing. That's great if you're doing some kind of B2B data/document exchange. Is it really well-suited for the web? Do you want to run a schema-validating XML parser inside a browser? If your server dishes up an XML doc, do you really want your browser to reject it?
- XML is extensible. Being able to extend a schema and thus add to a document is great, but do you really want data objects that have a lot more information than is needed by your browser? Perhaps you'll want to wait until the net neutrality debate is over before you answer that...
- XML allows your client and server to use the same data model. Again this sounds great, but there are big problems. First, it implies your server is storing everything (or a lot of things) as XML. You better have some really good reasons for doing this, as either your neglecting the considerable strengths of relational data storage or you're probably misusing it. Second, you're creating a strong coupling between the Models and Views in your system. I know this has become more popular as it is viewed as a tenet of "lightweight" development, but it is a design flaw. That doesn't mean you should never do it, just that it must be weighed against the positives that it would bring. In my experience, even when such tightly coupled systems work well at first, they become a nightmare on versions 1.1+
Again, it's not that I'm against XML on the browser... I'm just wary of some of the arguments for it. I think it is often a wash between the two technologies, which is why I say "so be it" when a web dev tells me they prefer JSON because it makes some of the programming easier.