The XML (extensible Markup Language) is used often XHR because this is a standard broadcasting language, what can be used by any programming language, and supported both server and client side, so this is the most flexible solution. The XML can be separated for more parts so a specified group can develop the part of the program, without affecting the other parts. The XML format can also be determined by the XML DTD or XML Schema (XSL) and can be tested.
The JSON a data-exchange format which is getting more popular as the JavaScript applications possible format. Basically this is an object notation array. JSON has a very simple syntax so can be easily learned. And also the JavaScript support parsing JSON with the eval function. On the other hand, the eval function has got negatives. For example, the program can be very slow parsing JSON and because of security the eval can be very risky. This not mean that the JSON is not good, just we have to be more careful.
My suggestion is that you should use JSON for applications with light data-exchange, like games. Because you don't have to really care about the data-processing, this is very simple and fast.
The XML is best for the bigger websites, for example shopping sites or something like this. The XML can be more secure and clear. You can create basic data-struct and schema to easily test the correction and separate it into parts easily.
I suggest you use XML because of the speed and the security, but JSON for lightweight stuff.
The important thing about JSON is to keep data transfer encrypted for security reasons. No doubt that JSON is much much faster then XML. I have seen XML take 100ms where as JSON only took 60ms. JSON data is easy to manipulate.
Faster is not an attribute of JSON or XML or a result that a comparison between those would yield. If any, then it is an attribute of the parsers or the bandwidth with which you transmit the data.
Here is (the beginning of) a list of advantages and disadvantages of JSON and XML:
Pro:
Con:
Simple syntax, only a handful of different data types are supported.
No support for comments.
Pro:
Con:
So in the end you have to decide what you need. Obviously both formats have their legitimate use cases. If you are mostly going to use JavaScript then you should go with JSON.
Please feel free to add pros and cons. I'm not an XML expert ;)
Processing speed may not be the only relevant matter, however, as that's the question, here are some numbers in a benchmark: JSON vs. XML: Some hard numbers about verbosity. For the speed, in this simple benchmark, XML presents a 21% overhead over JSON.
An important note about the verbosity, which is as the article says, the most common complain: this is not so much relevant in practice (neither XML nor JSON data are typically handled by humans, but by machines), even if for the matter of speed, it requires some reasonable more time to compress.
Also, in this benchmark, a big amount of data was processed, and a typical web application won't transmit data chunks of such sizes, as big as 90MB, and compression may not be beneficial (for small enough data chunks, a compressed chunk will be bigger than the uncompressed chunk), so not applicable.
Still, if no compression is involved, JSON, as obviously terser, will weight less over the transmission channel, especially if transmitted through a WebSocket connection, where the absence of the classic HTTP overhead may make the difference at the advantage of JSON, even more significant.
After transmission, data is to be consumed, and this count in the overall processing time. If big or complex enough data are to be transmitted, the lack of a schema automatically checked for by a validating XML parser, may require more check on JSON data; these checks would have to be executed in JavaScript, which is not known to be particularly fast, and so it may present an additional overhead over XML in such cases.
Anyway, only testing will provides the answer for your particular use-case (if speed is really the only matter, and not standard nor safety nor integrity…).
Update 1: worth to mention, is EXI, the binary XML format, which offers compression at less cost than using Gzip, and save processing otherwise needed to decompress compressed XML. EXI is to XML, what BSON is to JSON. Have a quick overview here, with some reference to efficiency in both space and time: EXI: The last binary standard?.
Update 2: there also exists a binary XML performance reports, conducted by the W3C, as efficiency and low memory and CPU footprint, is also a matter for the XML area too: Efficient XML Interchange Evaluation.
Worth to be noticed in this context, as HTTP overhead was raised as an issue: the IANA has registered the EXI encoding (the efficient binary XML mentioned above), as a a Content Coding for the HTTP protocol (alongside with compress, deflate and gzip). This means EXI is an option which can be expected to be understood by browsers among possibly other HTTP clients. See Hypertext Transfer Protocol Parameters (iana.org).
I found this article at digital bazaar really interesting. Quoting their quotations from Norm:
About JSON pros:
If all you want to pass around are atomic values or lists or hashes of atomic values, JSON has many of the advantages of XML: it’s straightforwardly usable over the Internet, supports a wide variety of applications, it’s easy to write programs to process JSON, it has few optional features, it’s human-legible and reasonably clear, its design is formal and concise, JSON documents are easy to create, and it uses Unicode. ...
About XML pros:
XML deals remarkably well with the full richness of unstructured data. I’m not worried about the future of XML at all even if its death is gleefully celebrated by a cadre of web API designers.
And I can’t resist tucking an "I told you so!" token away in my desk. I look forward to seeing what the JSON folks do when they are asked to develop richer APIs. When they want to exchange less well strucured data, will they shoehorn it into JSON? I see occasional mentions of a schema language for JSON, will other languages follow? ...
I personally agree with Norm. I think that most attacks to XML come from Web Developers for typical applications, and not really from integration developers. But that's my opinion! ;)
Source: Stackoverflow.com