In our daily web application development, we use XML or JSON as data interchange formats; but do we really know when to use XML and JSON. Here in this post i have tried to explain it.

XML and JSON both are the data interchange formats accessed over WEB. Both of these formats have their own pros/cons. No one is replacement of other. Use the right tool for the right job.

Talking about which one is better, is something related to the applications/requirements and the collaboration between client and server. Selection and strength of data interchange media types, is application specific.

Below i have given a summary of each format.

XML: Extensible Markup Language

1. An open standard for describing data defined by the World Wide Web Consortium (W3C).

2. XML lets Web developers and designers create customized tags that offer greater flexibility in organizing and presenting information. 

3. XML defines rules to mark-up a document in a way that allows the author to express semantic meaning in the mark-up. XML does not necessarily restrict the author to certain tags (elements) as HTML does.

4. Internet media type: application/xml

JSON: JavaScript Object Notation

1. A lightweight text-based open standard designed for human-readable data interchange.

2. A text-based format for exchanging objects.

3. It is an alternative to XML that is more concise because, unlike XML,  it is not a markup language that requires open and close tags.

4. It is derived from the object literals of JavaScript.

5. Design goals were for it to be minimal, portable, textual, and a subset of JavaScript.

6. Internet media type: application/json

 

JSON is built on two structures:

1. A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.

2. An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

 

Below are the differences between XML and JSON.

XML vs JSON

1.  JSON format is lightweight over XML.

2. JSON is recognized natively by JavaScript.

3. JSON can contain integers, strings, lists, arrays. XML is just elements and nodes that need to be parsed into integers and so on before it can be consumed.

4. The most important disadvantage of JSON is that the format is very hard to read for humans, and that, of course,    every single comma, quote, and bracket should be in exactly the correct place. While this is also true of XML, JSON’s welter of complicated-looking syntax, like the }}]} at the end of the data snippet, may frighten the newbies and make for complicated debugging.

5. Serialization format for your data, JSON is smaller, lighterweight and generally faster than XML.

6. JSON is best for consumption of data in web applications from webservices for its size and ease of use, especially due to the built-in support in JavaScript.
Imagine the computation overhead for parsing an xml fragment compared to the instant lookup in JSON.

7. XML is still great. JSON’s just the “latest and greatest” compared to XML.

8. For configurations file XML is better choice to make because it more human readable.

9. A browser JSON is faster to serialize/deserialize as it’s simpler, more compact and more importantly natively supported.

10. XML is document-oriented. JSON is data-oriented. JSON can be mapped more easily to object-oriented systems.

11. XML and JSON both use Unicode.That help in support for internationalization.

12. JSON does not have afeature, so it is not well suited to act as a carrier of sounds or images or other large binary payloads. JSON is optimized for data.

13. XML documents can contain any imaginable data type – from classical data like text and numbers, or multimedia objects such as sounds, to active formats like Java applets or ActiveX components.

14. JSON is a better data exchange format. XML is a better document exchange format. Use the right tool for the right job.

15. XML requires translating the structure of the data into a document structure. This mapping can be complicated. JSON structures are based on arrays and records. That is what data is made of. XML structures are based on elements (which can be nested), attributes (which cannot), raw content text, entities, DTDs, and other meta structures.

16. JSON is not extensible because it does not need to be. JSON is not a document markup language, so it is not necessary to define new tags or attributes to represent data in it.

 

Below is the final summary.

Summary:

1. For Data delivery between servers and browsers, JSON is better choice.
2. For storing Information in configuration files on the server side, XML is better choice.
3. On Browser Side: The speed and ease with which JSON is parsed and the ease of simple data retrieval from JavaScript object; makes JSON is a better choice.
4. Server Side: The querying data and format changes; makes XML a better choice.

Querying data: Using XPath, it’s possible to get direct access to a part of multiple parts of an XML data structure; no such interface exists for JSON. To get data from a JSON structure, you must know exactly where it is or else iterate over everything until you find it.

Format changes: You have your data in one format but you want it in another. If the data is in XML, you can write an XSLT template and run it over the XML to output the data into another format: HTML, SVG, plain text, comma-delimited, even JSON. When you have data in JSON, it’s pretty much stuck there. There’s no easy way to change it into another data format.

5. Security: JSON is less secure because of absence of JSON parser in the Browser; only way is to use eval() function. For security reasons on the browser side XML is better choice.
6. To extract data from database; XML is the only choice.

 

Below is the example; i used to explain each one’s usage in the Browser. This usage will also show you which one is easy to use on the browser side.

Example Data Operations:

XML

<?xml version="1.0" encoding="UTF-8"?>
<root>
	<data> 
		<id>1</id> 	               
		<name>PHP </name> 
	</data>
	<data> 
		<id>2</id> 	               
		<name>Table of Contents</name> 
	</data>
<root>

JSON

 {
                "data": [
                           {
                                "id" :    "1",
                                "name" :    "PHP"                            
                            },
                            {
                                "id" :    "2",
                                "name" :    "Table of Contents" 
                            }
]}

XML Responses + Accessing the data

The following code shows the source code used in retrieving the XML document. The getPage() function takes the URL from where you will retrieve the XML document. The function does so by setting up a reference to the XMLHTTP Request object, which does the task of retrieving and parsing the XML document as described in the XMLDOM. This is done after checking the status and availability of the document on the server.

var root = xhr.responseXML;
var dataElements = root.getElementsByTagName('data'); 
var idElementsValue = dataElements[0].getElementsByTagName('id')[0].firstChild.nodeValue;
var nameElementsValue = dataElements[0].getElementsByTagName('name')[0].firstChild.nodeValue;

JSON Responses + Accessing the data

While it might not be obvious, that lengthy string above is just an array, and once you’ve got that array in a JavaScript variable, you can access it easily. In fact, you can simply separate the array with period delimiters. So, to access the name of the first entry of the PHP documentation pages, you would use code like this in your JavaScript:

data.name[0];

Modifying JSON data

Just as you can access data with the dot and bracket notation shown above, you can easily modify data in the same way:

data.name[1] = "JSON is HERE";

That’s all you need to do to change data in a variable once you’ve converted from a string to JavaScript objects.

Hope this post helped you to understand the both XML and JSON. Please feel free to comment if you want to add something more on this.

 
 
 

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