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🧠 What Is XML?
XML (eXtensible Markup Language) is a markup
language designed to store and transport data. It is human-readable,
machine-parsable, and platform-independent, making it ideal for
scenarios where systems need to communicate data reliably.
Unlike HTML, which displays data, XML is used to describe
data.
🔑 Why XML?
📃 Anatomy of an XML
Document
A basic XML document consists of:
✅ Example
xml
<?xml
version="1.0" encoding="UTF-8"?>
<book>
<title>XML Basics</title>
<author>Jane Doe</author>
<price
currency="USD">29.99</price>
</book>
🔍 Explanation:
Component |
Description |
<?xml ... ?> |
Prolog: defines XML
version and encoding |
<book> |
Root element (every
XML must have one) |
<title>...</title> |
Child element |
currency="USD" |
Attribute on
the <price> element |
29.99 |
Text content |
🔤 Basic Syntax Rules
xml
<a><b></b></a>
✅
<a><b></a></b>
❌
🧱 Elements vs Attributes
✅ Example:
xml
<person
age="30">
<name>John Doe</name>
</person>
Element |
Use Case |
<name> |
Main data content |
age="30" |
Metadata / small info |
Tip: Use attributes for metadata and elements for
complex data.
🧼 White Space in XML
XML ignores extra white space outside of content:
xml
<name> John Doe
</name> // Output will
include all spaces
Use xml:space="preserve" to maintain formatting:
xml
<description
xml:space="preserve">
This is
indented
</description>
🔖 Self-Closing Tags
When an element has no content:
xml
<linebreak
/>
Equivalent to:
xml
<linebreak></linebreak>
🌳 XML Hierarchy and Tree
Structure
XML represents data as a tree, starting with a root
and branching into child elements.
Example:
xml
<library>
<book>
<title>Learn XML</title>
<author>Jane Doe</author>
</book>
</library>
Node Type |
Value |
Root |
<library> |
Child |
<book> |
Leaf |
<title>,
<author> |
🏷️ Tag Naming Rules
📦 Prolog and Declaration
The prolog comes at the very beginning:
xml
<?xml
version="1.0" encoding="UTF-8"?>
Attribute |
Description |
version |
XML version (usually
1.0) |
encoding |
Character
encoding (e.g., UTF-8) |
🔀 Real-World XML
Applications
Domain |
Use of XML |
Web Development |
SOAP, RSS, SVG |
App Development |
Android
AndroidManifest.xml |
Configuration |
Apache, Spring, Visual
Studio configs |
Content Publishing |
News feeds,
books (ePub) |
Data Exchange |
APIs, banking,
insurance, healthcare |
🔧 Creating Your First XML
File
xml
<?xml
version="1.0"?>
<contacts>
<contact>
<name>John Smith</name>
<email>john@example.com</email>
<phone>+1234567890</phone>
</contact>
</contacts>
Save as contacts.xml and open with any browser or text
editor.
🧪 Exercise: Create a
Product Catalog
xml
<?xml
version="1.0"?>
<catalog>
<product id="101">
<name>Laptop</name>
<price
currency="USD">899.99</price>
</product>
<product id="102">
<name>Mouse</name>
<price
currency="USD">25.50</price>
</product>
</catalog>
📚 Summary Table
Concept |
Key Points |
Element |
Data container using
<tag>value</tag> |
Attribute |
Metadata
inside the opening tag |
Well-formed XML |
Properly nested,
closed, and structured |
Root Element |
Single
top-level tag |
Case Sensitivity |
Tags must match
exactly in case |
Self-closing Tags |
<tag />
for empty values |
A: XML stands for eXtensible Markup Language.
A: Yes, <Tag> and <tag> are treated as different elements.
A: Absolutely. That's why it's called "extensible."
A: XML stores and structures data, while HTML displays it.
A: Its structured format and readability make it ideal for settings/configs.
A: Yes. Many enterprise and legacy APIs use SOAP, which is XML-based.
A: Not at all. While JSON is preferred for web APIs, XML is widely used in enterprise, publishing, and government systems.
A: You can validate it using DTD or XSD files or an XML validator tool.
A: Not directly. It needs to be base64 encoded first.
A: Notepad++, VS Code, XMLSpy, Eclipse, and Oxygen XML Editor are popular.
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