Can we replace XML with JSON entirely?

Question

I'm sure lots of developers are familiar with XML and JSON, and they've used both of them. Thus no point in explaining what they are, and what is their purpose, even in brief.

If we try to map their concepts, we can say (correct me if I'm wrong):

1. XML tags are equivalent to JSON {}
2. XML attributes are equivalent to JSON properties
3. XML tag collection is equivalent to JSON []

The only thing I can think of, which doesn't exist in JSON, is XML Namespaces.

The question is, considering this mapping, and considering that JSON is highly lighter in this mapping, can we see a world in future (or at least theoretically think of a world) without XML, but with JSON doing everything XML does? Can we use JSON everywhere XML is used?

PS: Please note that I've seen this question. It's something entirely different from what I'm asking here. Thus please don't mention duplicate.

Answer 1

The thing that gives XML its power and a lot of its complexity is mixed content. Stuff like this:

<p>A <b>fine</b> mess we're in!</p>

Don't even try to do that in JSON, or manipulate it in conventional programming languages. They weren't designed for the job.

This kind of question usually comes from people who forget that that the M in XML stands for markup. It's a way of taking plain text and adding markup to create structured text. It's quite handy for old-fashioned data too, but that's not what it was designed for or where its main strengths lie. There are plenty of ways of handling simple data, and JSON is one of them.

Answer 2

The main difference, I think, is in the fact that XML is designed to be self-explaining with its dtd's and everything.

With JSON, you have to assume alot about the data you are receiving.

Answer 3

A literal translation to JSON is often less succinct and less clear. Consider:

<foo>
   <x:bar x:prop1="g">
      <quuz />
   </bar>
</foo>

The most effective JSON representation I have seen of this:

{"localName":"foo",
 "children": // you need to have a special array to hold all children
 [
    {"localName": "bar",
     "namespace": "x"
        // once again, to ensure that there are no collisions,
        // attributes should be brought out into their own JSON structure 
        "attributes":[
            {"localName":"prop1",
             "namespace":"x",
             "value":"g"}
        ],
         "children":[
             {"name":"quux"}
         ]
     }
 ]}

Now, imagine that for an entire XML file. I am not saying that JSON does not have its place, but XML should not be ruled out.

Answer 4

JSON and XML are both ways of formatting data. Both are capable of doing it perfectly well, so can JSON do everything XML does? Yes.

But..... A more relevant question might not be what XML/JSON can do, but rather, what can you do with XML/JSON.

There are several things you can do with XML that I don't think you can with JSON, such as translate with XLST, search with XPath and validate with schemas. All very, very useful.

Answer 5

There's a lot of functionality using XSLT that may not be possible with JSON. So, if they're not functionally equivalent they couldn't replace each other.

Answer 6

The fact is, we're going to have to live with both for a long time, and being a JSON bigot is "considered harmful."

Answer 7

JSON is fairly new and legacy systems wont support it. Upgrading legacy systems is expesive and introduces bugs. JSON wont replace XML any time in the near future.

Answer 8

I'd say that cwallenpoole makes an excellent point. While most XML can be translated to JSON, whether doing so is better for it is a separate point.

JSON lends itself to data structures at least as well as XML and probably better, but XML reads much more naturally than JSON when marking up textual documents, where tags are used within a larger flow of text rather than simply as a way to delimit a hierarchy of fields.

While HTML 5 may have its own parser, that still leaves applications like DocBook.

Answer 9

It depends on the domain. In terms of web services? Absolutely. It's utterly shameful that vendors are still pushing SOAP on their customers. REST + JSON all the way.

Now, when you're talking about complex, structured data with style information like Docbook or other implementation? That's a proper domain for XML.

Answer 10

Why limit yourself to JSON when YAML is a super set and much more expressive and therefore powerful than XML or JSON.

That said, if you use the correct serialization frameworks you should be able to serialize and de-serialize all the above mentioned formats with a couple of simple lines of code.

Answer 11

It gets ugly when you try to model these two objects in JSON:

<customer><name>John Doe</name></customer>
<employee><name>John Doe</name</employee>

Using JSON as it is used to in 99% cases one gets lost with:

{ name: "John Doe" } 

And now you have to add some meta-structures and all the beauty of JSON is gone while you are left with the downsides.

Answer 12

I don't know if such a facility exists for JSON, but in .NET at least you can validate XML against a given schema. That's a valuable advantage of XML in my eyes.