<XML/>

eXtensible Markup Language

Press → or click to begin your journey

<xml>

</xml>

<data>

</data>

<tag>

</tag>

What is Markup?

Adding meaning to text through special annotations

📝

Plain Text

Just raw content without any structure or meaning attached

🏷️

Markup Language

Text + Tags that describe what the content means or how to display it

🔧

Purpose

Makes data readable by both humans AND machines

XML Defined

                eXtensible
                Markup
                Language
            

Extensible: Create your own custom tags - no predefined vocabulary
Markup: Uses tags to annotate and structure data
Language: A standardized way for systems to communicate
Self-describing: Tags explain what the data means

XML History

1960s

GML (Generalized Markup Language) created at IBM

1986

SGML becomes an ISO standard

1996

XML development begins at W3C

1998

XML 1.0 officially released!

XML Document Structure

Every XML document follows a precise hierarchy

<?xml version="1.0"?>

<root>

<child>

XML Declaration

The prolog tells parsers how to read the document

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

version

XML version (1.0 or 1.1)

encoding

Character encoding (UTF-8, ISO-8859-1)

standalone

External dependencies (yes/no)

XML Elements

The building blocks of every XML document

<element>Content goes here</element>

📦

Opening Tag

<element> marks where an element begins

📄

Content

Text, child elements, or mixed content

🔒

Closing Tag

</element> marks where it ends

XML Attributes

Add metadata and properties to your elements

                <book
                 id="001"
                 category="fiction"
                 lang="en">
                
  <title>The Great Story</title>
                
</book>
            

✓ Always quoted

Values must be in single or double quotes

✓ In opening tag

Attributes only appear in the start tag

✓ Unique per element

No duplicate attribute names allowed

Nesting & Hierarchy

Elements can contain other elements, creating a tree structure

<library>
  <shelf id="A1">
    <book>
      <title>XML Mastery</title>
      <author>Jane Doe</author>
    </book>
    <book>
      <title>Data Structures</title>
      <author>John Smith</author>
    </book>
  </shelf>
</library>
            

Creating XML Documents

Follow these rules for well-formed XML

Must have exactly one root element
All tags must be properly closed
Tags are case-sensitive (<Book> ≠ <book>)
Elements must be properly nested
Attribute values must be quoted
Special characters use entity references

Entity References

How to include special characters in XML

<

Less than: <

>

Greater than: >

&

Ampersand: &

'

Apostrophe: '

"

Quote: "

XML vs HTML

Click the cards to flip between the two!

XML

<person>
  <name>Alice</name>
  <age>25</age>
</person>
                            

Data description & transport

HTML

<div>
  <h1>Alice</h1>
  <p>Age: 25</p>
</div>
                            

Data display & presentation

Key Differences

XML ↔ HTML

XML Validation

Ensuring your XML follows the rules

Well-Formed

✓ Follows XML syntax rules
✓ One root element
✓ Properly nested tags
✓ Correct attribute format

Valid

✓ Well-formed AND
✓ Follows a DTD or Schema
✓ Correct element order
✓ Required elements present

DTD - Document Type Definition

A grammar that defines valid XML structure

<!-- DTD Definition -->
<!DOCTYPE note [
  <!ELEMENT note (to, from, heading, body)>
  <!ELEMENT to (#PCDATA)>
  <!ELEMENT from (#PCDATA)>
  <!ELEMENT heading (#PCDATA)>
  <!ELEMENT body (#PCDATA)>
]>
            

XML Schema (XSD)

A more powerful alternative to DTD

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="book">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="title" type="xs:string"/>
        <xs:element name="price" type="xs:decimal"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>
            

XML Namespaces

Avoiding naming conflicts in complex documents

<root
  xmlns:h="http://www.w3.org/TR/html4/"
  xmlns:f="http://www.furniture.com">

  <h:table>
    <h:tr><h:td>HTML Table</h:td></h:tr>
  </h:table>

  <f:table>
    <f:name>Coffee Table</f:name>
  </f:table>

</root>
            

XML in the Real World

XML powers many technologies you use daily

XSLT - Transforming XML

Convert XML into HTML, text, or other formats

Input XML

<catalog>
  <product>
    <name>Widget</name>
    <price>9.99</price>
  </product>
</catalog>
                    

→

Output HTML

<h1>Widget</h1>
<p class="price">
  $9.99
</p>
                    

XPath - Navigating XML

A query language for selecting XML nodes

// Select all book elements
/bookstore/book

// Select book titles
//book/title

// Select books with price > 30
//book[price > 30]

// Select first book
/bookstore/book[1]
            

Quick Quiz! 🎯

Which statement about XML is TRUE?

XML Best Practices

Use meaningful element names that describe the data
Keep consistent naming conventions (camelCase or snake_case)
Add comments for complex structures
Use indentation for readability
Validate with DTD or XSD for data integrity
Consider namespaces for large projects

Complete Example

<?xml version="1.0" encoding="UTF-8"?>
<!-- Online bookstore catalog -->
<bookstore xmlns="http://example.com/bookstore">
  <book id="bk001" category="programming">
    <title>Learning XML</title>
    <author>
      <firstName>Erik</firstName>
      <lastName>Ray</lastName>
    </author>
    <year>2003</year>
    <price currency="USD">39.95</price>
    <inStock>true</inStock>
  </book>
  <book id="bk002" category="web">
    <title>XML &amp; Web Services</title>
    <author>
      <firstName>Ethan</firstName>
      <lastName>Cerami</lastName>
    </author>
    <year>2002</year>
    <price currency="USD">44.95</price>
    <inStock>false</inStock>
  </book>
</bookstore>
            

Why XML Matters

🌍

Universal

Platform and language independent data exchange

📖

Self-Describing

Data carries its own meaning through tags

🔧

Extensible

Create custom vocabularies for any domain

✅

Validatable

DTD and XSD ensure data integrity

🔄

Transformable

XSLT converts to any output format

🏛️

Standard

W3C recommendation since 1998

</>

XML

✓

🚀

📝

💡

Thank You!

Now you understand the power of XML