CDATA section

CDATA Section

A CDATA section in XML (Extensible Markup Language) is a section of the document where the text data enclosed within it is not parsed by the parser. Characters such as "<" and "&", which are normally recognized as markup, are treated as regular text. This allows for the inclusion of material such as JavaScript code snippets, which might otherwise be mistaken for XML markup, without the need for escaping less-than and ampersand characters. CDATA sections are useful in XML documents that include characters that could be misinterpreted as XML markup.

Syntax

The syntax for a CDATA section is straightforward. It starts with "<![CDATA[" and ends with "]]>". Any text contained within these markers is ignored by the XML parser, which means it does not interpret any contained tags or entities as XML code. For example:

<![CDATA[
<This text will be ignored by the XML parser, including <, &, or any other characters that have special meaning in XML.>
]]>

Usage

CDATA sections are often used in XML files that contain code or raw text that could interfere with the parsing of the XML. This includes:

• Embedding JavaScript or CSS directly into XML documents
• Including XML or HTML code within an XML document without it being parsed
• Storing raw text that may contain characters that are otherwise reserved in XML

Limitations

While CDATA sections are useful for including literal text in an XML document, they have limitations:

• CDATA sections cannot contain the sequence "]]>", as it is used to mark the end of the CDATA section. If this sequence is needed within a CDATA section, it must be split in some way to prevent it from being recognized as the end of the CDATA section.
• CDATA sections are not a mechanism for security or for preventing the processing of data. Sensitive data should not be handled using CDATA sections without proper security measures.

Comparison with Character Escaping

An alternative to using CDATA sections is to escape special characters in the XML data. For example, "<" can be replaced with "<", "&" can be replaced with "&", and so on. This method ensures that the data is parsed and treated as text, but it can be cumbersome for large blocks of text or code.

See Also

• XML
• Markup language
• JavaScript
• CSS