Why XML tag data inside this <![CDATA[]]>

Question

I have seen in many XML file has the data inside this <![CDATA[ ]]>. What is the use of this?

Answer 1

From Wikipedia

A CDATA section starts with the following sequence:

<![CDATA[

and ends with the first occurrence of the sequence:

]]>

All characters enclosed between these two sequences are interpreted as characters, not markup or entity references. For example, in a line like this:

<sender>John Smith</sender>

the opening and closing "sender" tags are interpreted as markup. However, if written like this:

<![CDATA[<sender>John Smith</sender>]]>

then the code is interpreted the same as if it had been written like this:

<sender>John Smith</sender>

Check out the Wiki page for more details.

Answer 2

See CDATA at Wikipedia:

In an XML document or external parsed entity, a CDATA section is a section of element content that is marked for the parser to interpret as only character data, not markup.

That means the parser will not interpret any data contained in <![CDATA[ ]]>.

Lets say you want to store HTML as text in an XML document. This is wrong:

<root>
    <myhtml>
        <div><b>Foo bar</b></div>
    </myhtml>
</root>

The parser would try to parse <div><b>Foo bar</b></div> and create DOM elements. It would work in this example, but not for documents that conform to an DTD.

Instead, we want this:

<root>
    <myhtml>
        <![CDATA[ <div><b>Foo bar</b></div> ]]>
    </myhtml>
</root>

and <div><b>Foo bar</b></div> will become the content of a text node.