Question

Does anyone know when XML should be used instead of JSON and why?

Thanks

Answer 1

XML – pros

1. More strict – can be supplied along with Document Type Definition (DTD) which would allow you to analyze if provided XML data is syntactically correct
2. Namespaces – can help to mix data from various resources (for instance you can use namespaces from Spring Core and Spring Security, which helps to read and understand markup)
3. Can be navigated with XPath – helps to speed up looking for something deeply nested within markup
4. Huge sets of data can be parsed via lightweight processor like SAX parser
5. Used in some protocols (like SOAP) which could enforce using XML over JSON
6. Longer around the block – some older libraries can/use
7. Nice tools support (like native usage in Scala or IDE support)

XML – cons

1. Hard to read when it’s getting really big – harder to maintain
2. Comes with an overhead from all unnecessary tags (like <some_long_tag_name>...</some_long_tag_name> ecountered x1000 times in one file) which can have huge impact on network bandwith and disk usage

JSON – pros

1. Easier to read by humans

2. Native support in web browsers thanks to JavaScript

JSON – cons

1. Doesn’t contain type definition ("some_object" : "10" // String or Int?)

2. Lack of some sort of DTD (how can you tell that “some_object” is required?)

These are just major ones. Honestly one could write a book about it, so I don’t wonder whay are people downgrading this question… However I found appropriate to help you out a little.