What is XML?

XML stands for Extensible Markup Language. It is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. XML is widely used for data representation and data interchange between systems.

Key Features of XML

1. Extensible:

   • XML allows users to define their own tags and document structure. This flexibility makes it suitable for a wide range of applications.

2. Self-Descriptive:

   • XML documents are self-descriptive, meaning that the data is structured in a way that describes its own meaning. This makes it easier to understand the data without needing additional documentation.

3. Platform and Language Independent:

   • XML is not tied to any specific programming language or platform, making it a versatile choice for data interchange between different systems.

4. Hierarchical Structure:

   • XML data is organized in a tree-like structure, with a single root element and nested child elements. This hierarchy allows for complex data representation.

5. Human-Readable:

   • XML is designed to be easily readable by humans, which makes it easier to debug and understand.

XML Encoding

Encoding in the context of XML refers to the conversion of Unicode characters into their binary representation. This is important for ensuring that the data can be correctly interpreted by different systems and applications.

UTF Encoding

UTF stands for Unicode Transformation Format. It is a way to encode Unicode characters into binary format. There are several types of UTF encoding, with the most common being:

1. UTF-8:

   • Description: UTF-8 is a variable-length encoding that uses 1 to 4 bytes to represent each character. It is backward compatible with ASCII, meaning that the first 128 Unicode characters (U+0000 to U+007F) are represented using a single byte, making it efficient for texts primarily in English.
   • Usage: UTF-8 is widely used on the web and is the default encoding for many applications, including XML documents.

2. UTF-16:

   • Description: UTF-16 uses 2 bytes for most characters but can use 4 bytes for characters outside the Basic Multilingual Plane (BMP). It is commonly used in environments where memory usage is a concern, such as in Windows applications.
   • Usage: UTF-16 is often used in programming languages and frameworks that require Unicode support.

Example of XML

Here’s a simple example of an XML document representing a list of books:

xml
1<?xml version="1.0" encoding="UTF-8"?>
2<library>
3    <book>
4        <title>XML Developer's Guide</title>
5        <author>John Doe</author>
6        <year>2021</year>
7        <price>29.99</price>
8    </book>
9    <book>
10        <title>Learning XML</title>
11        <author>Jane Smith</author>
12        <year>2020</year>
13        <price>39.99</price>
14    </book>
15</library>

Explanation of the Example

• Root Element: <library> is the root element that contains all other elements.
• Child Elements: Each <book> element represents a book and contains child elements such as <title>, <author>, <year>, and <price>.
• Self-Descriptive: The tags used in the XML document describe the data they contain, making it easy to understand.

XML Documents must have a Root Element :

xml
1<?xml version="1.0" encoding="UTF-8"?>

xml
1<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
2<library>
3    <book>
4        <title>XML Developer's Guide</title>
5        <author>John Doe</author>
6        <year>2021</year>
7        <price>29.99</price>
8    </book>
9</library>

xml
1<message>Salary>2000</message>

xml
1<message>Salary&gt;2000</message>