JSON versus XML

As mentioned previously, one of the advantages of JSON over XML is that it's more compact. XML is considered by some to be overly verbose for its purpose. But what does this mean exactly? Consider the following XML data:

<classinfo>
    <students>
        <student>
            <name>Michael Smith</name>
            <average>99.5</average>
            <age>17</age>
            <graduating>true</graduating>
        </student>
        <student>
            <name>Steve Johnson</name>
            <average>34.87</average>
            <age>17</age>
            <graduating>false</graduating>

        </student>
        <student>
            <name>Rebecca Young</name>
            <average>89.6</average>
            <age>18</age>
            <graduating>true</graduating>
        </student>
    </students>
</classinfo>

This example contains information about three students in a class. Right away, there is some XML information that isn't entirely necessary: the <classinfo> and <students/> elements. These elements help to define the overall structure and meaning of the information, but the actual information you're interested in is the students and their information. Plus, for each piece of information about the students, the name of the information is repeated twice, although the actual data is repeated only once (for example, "name" appears both in <name> and </name>. Consider the same information formatted as JSON:

{ "classinfo" :
    {
        "students" : [
            {
                "name" : "Michael Smith",
                "average" : 99.5,
                "age" : 17,
                "graduating" : true
            },
            {
                "name" : "Steve Johnson",
                "average" : 34.87,
                "age" : 17,
                "graduating" : false
            },
            {
                "name" : "Rebecca Young",
                "average" : 89.6,
                "age" : 18,
                "graduating" : true
            }
        ]
    }
}

As you can see, a lot of the superfluous information isn't present. Since closing tags aren't necessary to match opening tags, it greatly reduces the number of bytes needed to transmit the same information. Not including spaces, the JSON data is 224 bytes, whereas the comparable XML data is 365 bytes, saving more than 100 bytes. (This is why Crockford, JSON's creator, calls it the "fat free alternative to XML.")

The disadvantage to JSON-formatted data as compared to XML is that it's less readable to the layperson. Because XML is verbose, it's fairly easy to understand what data is being represented. JSON, with its shorthand notation, can be difficult to decipher using the naked eye. Of course, an argument can be made that data exchange formats should never be viewed with the naked eye. If you're using tools to create and parse the data being passed back and forth, then there is really no reason to have the data be human readable. But this begs the question: Are there any JSON tools available? The answer is yes.